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BertZonn
February 11th, 2017, 06:49 AM
Hi folks, just stumbled on this forum and started reading about some Commodore computers.
But let me introduce myself first: My name in Bert Zonneveld (user: BertZonn why not?:D)
I was born in 1957 in the Netherlands but I moved to Belgium 12 years ago. I got married and devorced there and then remarried my current wife who is 23 years younger then me. We also have a beautiful 8 year old daughter. I started with Commodore when I bought a brand new VIC-20 with the datasette. I believe this was in 1982/1983. Paid topdollar back then. Later I bought the floppydrive (1540).
I've had a C64 also and the C128 (not 128D). I knew about the PET (2001) but it wasn't for sale anymore and not in color so I started with teh VIC-20.
If there are any questions about me don't hesitate to ask/mail me.

The reason I joined this forum is because I want to buy a vintage computer (PET model) and I have 2 options.

I can buy a PET 2001-32
I can buy a CBM-8032. I don't which one is the best choise.



The 2001 is a working 115V 60Hz model with C2N player and the 8032 is a 220V 50Hz model. I'm not sure the 8032 is in working condition.
Here in Belgium we have 220V 50Hz. Both computers are about 300-350 euro each (the Euro (€) is our currency and € 100 is $ 106)
So my first question is: which one should I buy?

Then I have a second question: Is it possible to connect a modern floppy drive (1541, 1570 or 1571) to these old computers?
The original Commodore drives are very expensive here and very hard to find.

If someone has any ideas please let me know.

Thanks!!

Ral-Clan
February 11th, 2017, 09:51 AM
An important point to remember is that if you want to play the old PET games, you really want a 40-column machine with a "Graphics Keyboard", not the "Business keyboard".

95% of the games and meant for the former machine (the PET 2001 or other 40 column PET).

BertZonn
February 11th, 2017, 11:26 AM
Thanks Ral-Clan,

So the better, more usefull computer would be the 2001-32.
This one is designed to work on 115V 60Hz. The seller has a transformer from 220V to 110V so that can't be a problem.
What about the difference in line- frequency (50Hz or 60Hz)? Could that be a problem?

3608036081

Bish500
February 11th, 2017, 11:26 AM
I agree with Ral-Clan. You want the 40 column screen and the graphics keyboard. It sounds like you'll have to rewire the 2001 for 220V, though.

At this time, there is no way I'm aware of connecting C64 drives to the PET. I had little trouble finding an affordable 8050 drive here, though (I had 2 come my way for less than $100 Canadian in a month).

Below is my PET 2001-N (32K) with 8050 Disk Drive

36082

BertZonn
February 11th, 2017, 11:33 AM
Hi Bish500,

nice machines you have. I worked with an early model PET in the eighties. The first one with the build-in cassetteplayer and I liked it a lot. That is the reason I wold like to have a Commodore PET myself.
Maybe I can find a affordable drive myself someday. I think I will start using cassettes in the beginning.

BertZonn
February 12th, 2017, 03:11 AM
Hello,

so I would be better of with the 2001-32N. Is it a problem to run the machine at 50Hz? On the back it says 115V 60Hz. There is a transformer (220V -> 110V) included in the sale.
Here are 2 pictures of the 2001-32N

3608836089

If I wanted to replace the transformer where could I buy a 220V type?

BertZonn
February 12th, 2017, 04:53 AM
Is it a problem if the computer is 60Hz and our mains is 50Hz?

BertZonn
February 12th, 2017, 08:39 AM
It seems I can't reply to this thread. I've tried several times but my threads don't appear of the forum. Maybe because I tried to upload 2 pictures?. :confused:

So I would be better of with the 2001-32N computer on 115V?
Then I would like to know if it is a problem to run the machine on 50Hz while the computer states 60Hz on the back.
I also would like to know where I could buy a transformer to change the unit from 115V to 220V.
The seller had an external transformer for 220V down to 110V and this appears te work. I'm affraid that somebody makes the mistake to plug in on 220V whitout the transformer. :rip:

BTW: how can I show pictures?

BertZonn
February 14th, 2017, 01:08 AM
Hello everybody, I'm sorry for the multiple posts above. I know a moderator is checking my posts before placing them but it took a while (not moderating on sundays?;)) so I thought my posts weren't coming through. My mistake because I'm very impatient/exited about the PET. To the moderator(s): please remove the non relevant posts above.

Ok, I bought the 2001-32N. Picked it up this morning. Man, it was dirty inside!! Full with dust so I took the vacuumcleaner and removed as much dust as possible.
36193 36194 36195 36196

Then I removed the mainboard and cleaned it as much as I could.
36197
I will do a better job next time but for now the mainboard is clean enough. I reconnected all the wires and switched the machine on.

There was no beep so there is something wrong there.
There is also a problem with the monitor. Instead of a nice black screen I have a green lit screen with very bright lines going across the screen. Some are horizontal and others go in a slope to the next horizontal line.
Could this be a problem of running on 50Hz instead of 60Hz?

36198

I also see (barely)
### COMMODORE BASIC ####
31743 BYTES FREE
READY.

When I type the command LOAD it asks me to PRESS PLAY ON TAPE #1
When I do so it shows OK and SEARCHING

So I think the computer works fine at this time.

I would like to do a full restoration of this computer so I'm going to clean the keyboard (contacts) and a news coat of paint on the outside.
I think I will post pictures of the restoration here on the forum.

Does anybody have a solution for the bright lines on the monitor? The monitor is 9"

MikeS
February 14th, 2017, 11:12 PM
Congratulations, and welcome to the world of PET owners!

Wow; that was dusty for sure!

The 2001 models do not have a beeper, so no beep is not a problem.

Regarding the screen, try turning the brightness knob sticking out the back of the monitor.

Good luck!

m

KC9UDX
February 14th, 2017, 11:29 PM
50Hz shouldn't be a problem, I don't think. But, like MikeS said, hopefully your raster lines and background brightness are a simple turn of the accessible pot on the back. If not, surely someone here will walk you through component diagnosis and replacement.

You may not have to disassemble the keyboard to clean it; just press the keys a lot. It sounds odd, but it's true in a lot of cases. Mine must corrode, because if Iet it sit for a few months then I have to work the keys again.

You have an earlier BASIC which I don't care for, but a lot of collectors prefer. You may want to upgrade to 4.0, though, I don't really think there's anything to lose other than some bugs and missing features.

BertZonn
February 14th, 2017, 11:31 PM
Hi Mike,

When I examened the board a second time after cleaning I found that there was no beeper at all so that problem was solved very fast!

Turning the knob on the back was the first thing I did but no results. After that I opened the back of the monitor and I found a second potentiometer but the only difference was the hight of the image on the screen.
No solution there I'm afraid.

Still hoping somebody has the answer.

Bert

BertZonn
February 14th, 2017, 11:46 PM
Hi KC9UDX,

I thought so too that 50 or 60 Hz would not make a difference. The incoming power from the tranformator is about 12V AC and it turned into 12v DC in the monitor.
The turn on the pot in the back was not the solution. Also the second pot on the board inside the monitor idn't help. This one is for the height of the image on the screen.

How about the upgrade to basic 4.0? Where can I buy another ROM and how difficult is the installation procedure? Is it just a matter of exchanging ROMs or is there more to it?
Basic 4.0 seems interesting because I would like to upgrade (in the future) with (a) diskdrive(s) of maybe the PETDISK (or equal)
I've also noticed that there are 3 empty sockets on the motherboard. U3, U4 and U5. What are these sockets for? I guess expansion but what kind of?

I know, it's a lot of questions but I want to enjoy this computer as much as possible. I want to start again with programming in Basic like I used to do on my VIC-20, C=64 and C=128

Bert

Bish500
February 15th, 2017, 06:28 PM
Congratulations on getting a PET! In most monitors, there is something called the B+ adjustment, which is often a potentiometer (a small screw on the monitor chasis circuit board). It increases the brightness to the screen, but is a different setting than the brightness pot. The theory is that as the electronic components like capacitors on the board start to dry out, you can increase the B+ to compensate for it. Sometimes it can get jarred in transport, and then your screen looks too bright (once you set it, use a drop of nail polish to lock it in place). I have never looked at the PET monitor chasis board, so can't tell you where that pot might be...take a careful look. It should look similar to the vertical height adjustment. I work with arcade game monitors, so it may also be a colour monitor thing, and you may not have one on the PET monitor. Just worth considering.

As for BASIC 2 - it shouldn't cause you any problems, until you go to use it with a disk. The disk based commands are really clunky - especially when using a dual drive. I'm considering this product, which looks like it allows you to switch between versions of basic, and different memory configurations: https://www.thefuturewas8bit.com/petromram.html

KC9UDX
February 15th, 2017, 07:13 PM
BASIC 2 isn't so bad, if you're used to it on the C64 and VIC20. But 4 is otherwise much nicer.

You should be able to download 4 and burn your own EPROMs, if you have that capability, but I've no idea where to get them, perhaps the Zimmer site.

You'll use one of those empty sockets if you do upgrade. Otherwise they were mostly used for software protection schemes, and less often for BASIC enhancement and the likes.

I could fix your monitor if I had it in front of me, but I'm not very good at doing it remotely. I would not adjust the B+ without measuring it and finding out if it's actually incorrect first. But you could do that, if you don't have that capability. I'd suspect component failure or weakening though, and would want to replace them, if so.

MikeS
February 15th, 2017, 07:23 PM
Hi Mike,

When I examened the board a second time after cleaning I found that there was no beeper at all so that problem was solved very fast!

Turning the knob on the back was the first thing I did but no results. After that I opened the back of the monitor and I found a second potentiometer but the only difference was the hight of the image on the screen.
No solution there I'm afraid.

Still hoping somebody has the answer.

Bert

Since they stick out the brightness controls are a little vulnerable, so just check that everything is OK where it mounts on the board; if it isn't that, then it probably is a problem with the HV regulation, which could be a little trickier.

m

dave_m
February 15th, 2017, 07:54 PM
Since they stick out the brightness controls are a little vulnerable, so just check that everything is OK where it mounts on the board;



Yes, I agree. The brightness potentiometer is probably broken or more likely one of the three solder joints is open. Check connections with power off on pot R253. See [layout (http://zimmers.net/anonftp/pub/cbm/schematics/computers/pet/2001N/321446.gif)]

BertZonn
February 15th, 2017, 11:03 PM
Hi Dave_m,

well, turning on the brightness knob does work but everything on the screen gets brighter. The text but also the lines. I think there might be a problem in the HV part (HV = High Voltage I suppose?)
There is a guy here in belgiu who said it could also be a problem with the motherboard since all signals to the monitor come direct from the motherboard. I don't have the experience so I can't judge if he is right or wrong. He claims he can repair all Commodore problems. Today he is going to a meeting of Commodore fans/freaks in Holland/Netherlands and he will be doing some research on this matter for me at some members of that Commodore club. Hope he will find some answers. The layout you provides is not the correct one. Maybe mine is older of newer.
Layout: ftp://www.zimmers.net/pub/cbm/pet/schematics/2001/video-layout.gif
Schematics : ftp://www.zimmers.net/pub/cbm/pet/schematics/2001/video-3.gif

I have done some research on Basic 4.0 as well and I found a guy in the UK who makes and sells a lot of computerhardware, also for the commodore PET: http://www.tynemouthsoftware.co.uk/Shop
Could be interesting. As soon as my PET is healthy again I want to buy the PET micro SD.
36253

and maybe later the PET ROM/RAM board
36254

But first thing first. The monitor must be in perfect working order.

One more thing about this computer: Like I said this is a 115V 60Hz model. When I took the mb out for cleaning I noticed that all 3 voltage regulators were replaced. Did some idiot connect the computer to 220 Volt mains????? If so, could the mb be damaged and could that be the source of the problems I have with the monitor?
I don't know but why would someone replace the voltage regulators?

@KC9UDX
I'm used to programming in Basic on the C64, C128 and the VIV-20 so that would not be a problem. I'm a bit rusty on programmingh but with a little practice it will all come back to me. Programming is the main reason I bought this computer. Programming and the urge to own a classic vintage computer. ;)

Thanks for now for all of your answers. I still hope someone has the ultimate answer for the problem with the monitor.

Bert

BTW. I hope I don't make too many mistakes in my English.

BertZonn
February 16th, 2017, 12:39 AM
Hi guys, I've been exploring the internet again to find information on my problem with the monitor.
Now I met a man who also develops a lot of hardware for Commodore computers. He claims he is able to repair my PET so I will make an appointment to meet him in Brussels.
It seems he is a hardware developer and his company has developed an interesting device.

Remember my question in my first post:
Then I have a second question: Is it possible to connect a modern floppy drive (1541, 1570 or 1571) to these old computers?
The original Commodore drives are very expensive here and very hard to find.

Well, his company has developed the PetBus which can connect a PET with parallel IEEE488 to C64 serial IEE488 devices and vice versa.
The device also has RS232 to monitor the dataflow and a network connection to connect 2 or more PetBus boards.
You can read all about it here: http://chipitos.be/main/index.php/mainproject/petbus

Hope this is helpful to the PET lovers who would like to have an inexpensive floppydrive on their PET.
I don't know what it will cost but I will try to find out.

Bert

daver2
February 17th, 2017, 05:07 AM
It is highly improbable that a faulty main board will give you the superbright display on the monitor.

The signals that come from the main board are the horizontal and vertical synchronisation signals and the video signal. The synchronisation signals cannot cause this symptom - and it is also highly unlikely that the video signal could either.

If you don't fancy tackling the monitor problem yourself - you could also find a local TV repair man. The schemtics for the monitor are available from the Bo Zimmer's website for his reference.

I have just had a look at the monitor schematic (I am guessing it is this one? http://www.zimmers.net/anonftp/pub/cbm/schematics/computers/pet/2001N/321445.gif). There are very few components in this part of the circuitry.

The HV transformer T702 (yes, HV = High Voltage. EHT = Extra High Tension. Both = will kill you unless you are careful!) produces a voltage on tag 8. This is rectified by diode D752 and smoothed by capacitor C752 to produce a dc voltage of about -45V (relative to ground). This voltage is fed to the brightness potentiometer R253 (can't quite read this on the schematic). The wiper of this potentiometer is further smoothed by C251, where it is fed to Grid 1 of the CRT via the green wire.

You should be able to measure approximately -45V across capacitor C752 (with care...) and a variable voltage between -45V and 0V across C251 when the brightness control is turned from end to end.

And yes, 50 Hz isn't a problem for a 60 Hz transformer.

Dave

KC9UDX
February 17th, 2017, 05:26 AM
Yes, a TV repairman is much more likely to solve this problem than most anyone dealing normally with computer hardware.

Bert, your Englisch may be besser than mein!

Ral-Clan
February 17th, 2017, 05:40 AM
I'm sure I'm repeating information here, but just in case you still haven't heard the message: please be very careful inside the monitor. There are some dangerous voltages there.

KC9UDX
February 17th, 2017, 05:47 AM
No user serviceable parts inside. Pilot lamp soldered in place.

BertZonn
February 17th, 2017, 07:38 AM
For all readers:

Try finding a TV repairman who is able to repair an old monitor/tv with a CRT. I think they've al died now. I've contacted several commercial repair centres but they are not able to find me a repairman. Also shops that sell TV's can't repair the old CRT TV's. CRT is too old. The only TV's they can repair are the LCD types. I think they (the technicians) now how to replace a module in the TV because they connect a laptop to the TV and the laptop tells them what is faulty. Real repair men are very hard to find. Hope the man in Brussels can help me.

I am VERY carefull inside the monitor. I know there are very high voltages on the HV transformer en behind the rubber plug on the tube. I'm not messing with this stuff and I want to leave it to qualified technicians.

@KC9UDX
Bert, your Englisch may be besser than mein!

I suppose you are German? ;)

KC9UDX
February 17th, 2017, 01:33 PM
I suppose you are German? ;)

Only on Freitag. :)

Ral-Clan
February 17th, 2017, 03:55 PM
BertZonn,

Even if you are never able to repair the monitor (and I think you probably will be able to find someone), I seem to remember that the PET 2001 could be fairly easily connected to an external composite/luma input on an external monitor / TV. I can't find the information anywhere, but I think it was a fairly simple interface connected to the user port. Does anyone know about this?

EDIT: here is one device:

http://www.dasarodesigns.com/product/commodore-pet-video-mixer/

BertZonn
February 18th, 2017, 04:08 AM
BertZonn,

Even if you are never able to repair the monitor (and I think you probably will be able to find someone), I seem to remember that the PET 2001 could be fairly easily connected to an external composite/luma input on an external monitor / TV. I can't find the information anywhere, but I think it was a fairly simple interface connected to the user port. Does anyone know about this?

EDIT: here is one device:

http://www.dasarodesigns.com/product/commodore-pet-video-mixer/

Hi Ral-Clan,

I've been to the website and I found it is a small circuitboard that is placed on the connector J7 on the PET motherboard. Normally the videoconnector for the monitor is connected to this connector.
The circuitboard transforms the digital signal from the motherboard to a composite videosignal that can be used by any monitor with a composite video input. I think even a LCD television with a SCART connector will do.

I could not find any means of purchasing one of these boards on the website but I found an old listing on Ebay. I think however that they are out of stock.
Anyway, the seller doesn't sell these boards anymore.

I am not able to make a board like this myself so I must find a seller.
Hope I can fing one.

Bish500
February 18th, 2017, 09:01 AM
Here is a schematic to get composite video out of a PET

36288

BertZonn
February 18th, 2017, 02:07 PM
Here is a schematic to get composite video out of a PET

36288

Yes, that's the one I saw. I can't make it myself because I don't have the equipment for it. They used to be for sale on Ebay some time ago but not anymore.
I wrote them an email hoping they can help me.

Bert

Bish500
February 18th, 2017, 04:52 PM
http://www.dasarodesigns.com/product/commodore-pet-video-mixer/

Apparently this is the person that produces the video mixer. There's no price listed on the website, but there is contact information. Perhaps you can write him an e-mail and ask if he has any available.

BertZonn
February 19th, 2017, 12:08 AM
http://www.dasarodesigns.com/product/commodore-pet-video-mixer/

Apparently this is the person that produces the video mixer. There's no price listed on the website, but there is contact information. Perhaps you can write him an e-mail and ask if he has any available.

Correct, that is the man I wrote to.

daver2
February 19th, 2017, 12:16 AM
The PCB layout is available from his website. You download it (plus a copy of expresspcb - also free) and you can order a 1 off PCB for the unit.

The components are (I think) still all available for purchase from the likes of Digikey, Farnell etc.

A soldering iron and some solder and you have one made…

Dave

Bish500
February 19th, 2017, 05:47 AM
The PCB layout is available from his website. You download it (plus a copy of expresspcb - also free) and you can order a 1 off PCB for the unit.
Dave

My mistake. I thought he was selling completed products.

BertZonn
February 20th, 2017, 01:30 AM
Just got mail from a man named Sean from Commodore Computer Club – USA Vancouver, WA – Portland, OR – PDX Commodore Users Group. http://www.commodorecomputerclub.com/

He advised me to recap the PCB of the monitor because all the capacitors are over 30 years old. Should I replace all capacitors or only the electrolitic ones? There are some capacitors with a sparkgap (?) and I'm not shure where I could buy those capacitors.

And what about the capacitors on the mainboard of the computer? Should I recap this PCB also?

Bert

daver2
February 20th, 2017, 03:03 AM
I (personally) wouldn't. You could end up replacing all the capacitors to still not fix the fault!

Get the fault fixed first and then consider your options.

The only capacitors to suffer from aging are generally electrolytics and tantalums - so they would be first on your 'hit list'. I have seen damage on ceramic disk capacitors before now - but not through aging but something chewing them! I have had a couple of tantalums explode on me.

My suggestion would be to replace the electrolytics and tantalums on power rails only - and see how the rest go with time (but only after you get the existing fault fixed - which may (of course) turn out to be a capacitor). Have you done the checks I suggested on the brightness voltage (-45V). There is what looks to be a polarised (electrolytic?) capacitor in here (C752) if you want somewhere to start.

Dave

KC9UDX
February 20th, 2017, 05:17 AM
I never shotgun replace all the condensers. By the way, there's no reason to ever change a spark gap unless it has physical damage.

I always do as Dave suggests, and diagnose and fix the problem. After that, I start replacing suspect components. Here's one reason why: If you find through diagnosis that one capacitor is bad, you may find that there's a resistor network, or some other component near it that is bad, which caused the condenser to fail. If you just replaced all the condensers and the problem went away, that same one would fail again in a short while.

I have seen ceramic disk capacitors go bad. Usually from over voltage. But I've also seen ones that were just cracked in two for no apparent reason. Very, very rare though.

BertZonn
February 24th, 2017, 06:09 AM
Well, today I carefully discharged and removed the CRT and PCB. When I removed the PCB I did cut the 4 wires leading to the yoke but I left a bit of colored wire on it so I know what color goes to what connection. I also took a picture, just to be on the safe side. I cleaned the PCB of the monitor because here was a lot of dust too, just like on the CPU board.
The PCB has a number on it: 320084-02, copyright 1977

You may call me cocky but I ordered all new electrolitic capacitors. I also ordered all new transistors and diodes, even the 33V zener. It is a bit of work to replace them all but who cares? I like beeing busy. Tomorrow I will pick up all the items in our local electronics shop. The total costs are very low so why not? I paid € 12,45 that is bit over $ 13 for all items.

After that I will go to the DIY shop and get me a spray can with glossy off-white paint that matches the original paint of the PET as much as possible. I will get me a can with glossy black also because the underside of the PET is rusty on the outside. Maybe even some new rubber feet to complete the works.

While soldering I will resolder all other point on the PCB just to be sure there isn't a bad connection after all those years.
Hopefully the recap job (capacitors, transistor and diodes) does the trick for my problem. If not, then I'm sure it's not the components on the PCB and we must search further.

I'll keep you informed!!

Bert

daver2
February 24th, 2017, 10:06 AM
I have just looked up some posts I made on VCFED about a similar problem on another PET. My post stated (paraphrased):

With 0V on the green brightness lead (tube Grid 1) - this gives maximum brightness.

A more negative voltage causes the screen brightness to become dimmer.

The voltage across C752 was measured and found to be -33V instead of -45V.

Unfortunately, the fix was never completed due to the main board dying!

I would (personally) replace D752 and C752 (if you are going to blitz replace things) and see if that actually fixes the problem. If not, by all means replace all the diodes, transistors and capacitors.

It could also be the transformer T702 (a faulty winding not producing the required negative brightness voltage) so replacing everything may still not result in a resolution. It makes sense to measure the d.c. voltage across C752 to make sure there is -45V present. If you are getting some sort of full-screen picture, then the EHT and horizontal deflection voltages are present (both of these originate from T702). If you are not getting the -45V across C752 - and you have replaced D752 and C752 - then it is highly probable that T702 is faulty and replacing everything will not help.

You could see if the winding is open circuit on T702 by measuring the resistance between pin 8 of T702 and the positive end of C752 (ground) with the power off. I am not sure what the resistance should be - but it shouldn't be open circuit.

Dave

KC9UDX
February 24th, 2017, 01:19 PM
And T702 may be unobtainable. Doing a ton of unnecessary work prior to learning that you have to go on a five year search for a part can destroy your enthusiasm.

MikeS
February 24th, 2017, 02:00 PM
Do those part numbers correspond to the board/schematic in question?

BertZonn
February 24th, 2017, 02:17 PM
Ok, I tried to find the parts that were mentioned but T702, C752 and D752 are not in the schematics. The one that most likely would be the correct one is:ftp://www.zimmers.net/pub/cbm/pet/schematics/2001/video-3.gif

Why? It's the only one where C22 is 47µF and so it is on my PCB and most of the other parts check out to be the same on the PCB and in the schematics. An exception are the 3 transistors Q6, Q7 and Q8. The schematics tells me they should be 2N3903 but they are 2N3904 on the PCB.

If transformer T1 or T2 is defective then I will have a problem because these will be very hard to find.

I'll try to explain why I want to replace all transistors; Some years ago I repaired a lot of Akai reel to reel tape recorders. All the Akai models had the same problem. The transistors aged too much and the quality of the sound got worse. After replacing the transistors and capacitors (and some finetuning) the taperecorders sounded much better. I don't mind the work because I like to tamper with a soldering iron.
And for the price? Who cares about $13?

Maybe I get the job done and if not then I must search some more. Like I said before there is a man in Brussels who has some spare parts. If needed he might be the helping hand I could use.

BertZonn
February 24th, 2017, 02:21 PM
Do those part numbers correspond to the board/schematic in question?

No, they don't correspond to my schematics. I think my PCB corresponds to : ftp://www.zimmers.net/pub/cbm/pet/schematics/2001/video-3.gif

I think my PET might be a inbetween model or a very early 2001N with the schematics for the 2001.:confused:

daver2
February 24th, 2017, 10:57 PM
So the components to check in this case would be: R41, CR16, C22 (which should have -30V across it), R9 (the brightness potentiometer) and R10. I would also clean the spark gap on SG1 if you haven't already.

I also enjoy using a soldering iron. I constructed some diagnostic boards for my PDP-11/45 at a recent vintage computer event - however, after spending a considerable amount of my time doing this, I know I will have a working 'thing' at the conclusion.

Yes, Commodore occasionally had 'mixed' systems when changing from one revision of a machine to a new one.

There is a major difference between a monitor and a tape recorder in this case. I am 99% sure that it is the brigness supply that is faulty in your case. The driver components are 'switched' rather than operate in a linear fashion (as your tape recorder does). As you can see a picture on the CRT, then parts of this circuit appear to be working correctly, so replacing anything upstream of the transformer (in this case) I would consider to be unnecessary at this point in the fault rectification process. I would concentrate on the components after the transformer in the brightness circuit first.

I am just trying to save you some time and heartache - but by all means feel free to do whatever you are comfortable with.

Dave

BertZonn
February 25th, 2017, 10:05 AM
Ok, in my rage to replace all suspecious components :rolleyes: I have replaced CR16 and C22. I checked R41 which is 10 ohms. R9 checks out to be 104kohm. So those items are ok. Cleaning the spark gap? How can I do that?

I also painted the outside of the casing;
36549

and the inside;
36550

On Youtube I saw a guy who painted his PET red on the inside. I had a spray can with blue paint and I like it.

KC9UDX
February 25th, 2017, 10:11 AM
A spark gap condenser is very much like a spark plug for an internal combustion engine. Except there's just a couple of electrodes soldered to the board. Sometimes they have a plastic housing around them.

Because there is high voltage present at the electrodes, they attract dirt from the air. So typically they have a layer of fuzz on them. If they're not enclosed, cleaning is just a matter of wiping with a wet cotton swab. If they are enclosed, you may have to remove the plastic, which sometimes means breaking it. If enclosed though, I wouldn't worry about it unless it's firing (you'll hear some sharp snap noises if it is, or a continuous buzz).

daver2
February 25th, 2017, 10:14 AM
Nice paint job...

Just use a clean cloth to clean any dust and debris that may have accumulated off the spark gap.

If you get something that is conductive on there - it may prevent the brightness control from working correctly. Unlikely though. You could also suck any dust and debris off with a hoover (vacuum cleaner).

Dave

BertZonn
February 25th, 2017, 01:51 PM
The spark gap. When I look at my PCB I see some ceramic capacitors with a cut in it. No plastic. I will try to clean the gap/cut with the vacuumcleaner tomorrow.

36561

BertZonn
February 26th, 2017, 07:04 AM
Assembly!!

Finally the paint is dry and I can start putting all loose components back together again. First picture is of the inside of the monitor after assembly:
36587 36588

Then I started mounting all parts for the powersupply and the motherboard and I cleaned the edge connectors of the motherboard. I removed the blue paint where the copper holder must be mounted so the motherboard is connected to the ground. (Top left mountinghole on the mb near the power supply)
After that I mounted the powersupply and its capacitor and then I mounted the motherboard. I made all the necessary connections for the keyboard, powersupply and the wiring for the monitor:
36589 36590 36591

And there it is, the headless beast:
36592 36593

Mounting the monitor with the plastic bezel on top of the case:
36594 36595
BTW: The painting you can see on the wall was made by my grandfather in 1957.

Then the most scary part...... Switching on!!
Unfortunately the fault is still there. What a bummer!!
36596 36597

But I will not give up. There must be a solution somewhere. Now I have a beautiful and clean Commodore PET but unfortunately with a monitor problem.
I enjoyed myself yesterday with replacing a lot of components and doing the paintjob.

Like I said in a former post I checked the pots and some mentioned resistors, replaced all of the diodes, transistors and capacitors.

I've read something about an different EPROM for 50Hz and 60Hz machines. Could that be the problem or it that solution for some other Commodore PET?
Any suggestions are welcome!!

Bert

daver2
February 26th, 2017, 07:21 AM
As you say, a nice clean PET with nice new components - but with a fault.

The simple answer is that the 50/60 Hz ROM will not fix this - as you can see the correct video display on the actual monitor (I can just make out the word "READY") - just swamped by the over brightness.

Did you measure the Voltage across C22 I asked you to (which should be -30V)?

Dave

MikeS
February 26th, 2017, 08:31 AM
...
Did you measure the Voltage across C22 I asked you to (which should be -30V)?
Yeah, we're all breathlessly waiting for that; since the horizontal and HV seem to be OK, it's likely a trivial problem.

I'd also measure the voltage on the wiper of the brightness control as you turn it from one end to the other (SG1 or R10 if we're on the right schematic)

It does look pretty though; very nice!

BertZonn
February 26th, 2017, 09:40 AM
Ok, you all can start breathing again. :D

The voltage over C22 = 35,4 Volt DC
The voltage on the wiper of the brightnesscontrol (R9) varies from 0 to 35,4 Volt DC where 0 Volt is maximum brightness and 35,4 Volt is minimum brightness.
The intensity of the bright lines goes up and down too.
All voltages were measured between the mentioned testpoint and ground (case of the monitor)

(and I'm sure we are on the right schematic.) :wink:

daver2
February 26th, 2017, 09:58 AM
When you say 35.4V do you mean -34.5V? The voltage should be relative to the positive (+) side of C22 (i.e. the ground rail).

The brightness voltage appears to be correct (assuming it is negative rather than positive), and you can see the brightness of the picture varying as you change the brightness potentiometer - but not by much. Is that what the symptom is?

I am running out of ideas in the brightness side of the circuit.

Looking at the cathode of the tube (where the video signal is processed) there is very little in here (apart from a few insignificant capacitors and resistors) that you haven't changed. One thing I would, however, like you to check is the voltage across CR7 (a 33V 1W Zener diode). I assumed you replaced this device in the last blitz? This voltage should be approximately 33V if things are working correctly.

The only thing I can think of after that is that you have a higher than expected boost voltage (this should be 85V or 95V), or the tube is defective...

I hate monitor faults. Give me logic any day!!!

Forgot to ask - do you have access to an oscilloscope?

Dave

BertZonn
February 26th, 2017, 10:35 AM
You are correct, it is -35,4 V DC relative to the ground rail. In my case the monitor housing. Also the voltages on the wiper are 0 to -34,5 V DC.

Like I said in the beginning, I don't think the fault is in the brightness control. The brightness control does its job but the bright lines should not be in the picture. I don't know what is causing them. The lines are much brighter then the text. I can make the text brighter but then also the lines get brighter. There must be some external signal casing these lines to appear but from where? Further the monitor seems to work perfect except for those very bright lines.

About the osciloscope; no, no scope present anymore. I used to have one but I sold it some years ago.
I did buy this chinese DIY kit ( DSO138 ) but that will take some weeks to arrive. => http://www.banggood.com/DSO138-DIY-Digital-Oscilloscope-Kit-SMD-Soldered-13803K-Version-p-984002.html

36608

No idea about the quality yet. The reviews look good.

daver2
February 26th, 2017, 11:23 AM
The video signal should be blanked during the horizontal and vertical flyback time.

This is accomplished on http://www.zimmers.net/anonftp/pub/cbm/schematics/computers/pet/2001N/320349-8.gif (assuming I have got the correct schematic) at G11 pin 2 (and possibly other places).

I am now backtracking a bit and wondering if the blanking during the horizontal and vertical retrace is not working whether this will give the symptoms as shown.

Anyone else care to chip in?

Dave

BertZonn
February 26th, 2017, 11:49 AM
Hi Dave,

thanks for thinking with me. When the motherboard was removed I checked for a number on it in order to find the correct schematics. The number I found on the mb is 320350 - 3
Maybe that might be useful to find the correct schematics.

Are you saying that the problem could be in the motherboard and NOT in the monitor?
Disconnecting J7 on the motherboard gives no solution. I get a very bright green dot in the middle of the screen and it takes a while to disappear after switching off the PET.

Bert

KC9UDX
February 26th, 2017, 11:53 AM
Are you able with the brightness control to completely dim the display do that it's all black and nothing is visible? If so, you probably have a logic problem in the video section of the PET board.

If not, from this distance all I can think is, in order, flyback, and CRT. But I'd also like to know if the B+ voltage is correct. I'm fairly good at fixing monitors and TVs on my bench. But I'm not very good at doing it over the phone or internet. :)

BertZonn
February 26th, 2017, 12:15 PM
Are you able with the brightness control to completely dim the display do that it's all black and nothing is visible? If so, you probably have a logic problem in the video section of the PET board.

If not, from this distance all I can think is, in order, flyback, and CRT. But I'd also like to know if the B+ voltage is correct. I'm fairly good at fixing monitors and TVs on my bench. But I'm not very good at doing it over the phone or internet. :)

The B+ ; is that the 85V or 95V boost?
What should it be? 85V or 95V

Bert

daver2
February 26th, 2017, 12:36 PM
It's no good disconnecting J7 as this disconnects the horizontal and vertical synchronisation signals that the monitor uses to produce the internal high voltages for the tube. The result is that the horizontal and vertical signals disappear and the electron gun is not deflected (hence the single spot in the centre of the screen) and the high voltages disappear with time because there is no horizontal drive (hence the dot disappears over time).

Possibly yes, the fault is on the main board and not the monitor if the video blanking signals are missing. This would (however) be a strange (and highly improbable) but not impossible fault.

Yes, B+ is the boost voltage. The numbers in parenthesis (according to note 5 of the monitor schematic) are for the 'DOK' version (whatever that is?)

Dave

BertZonn
February 26th, 2017, 12:54 PM
It's no good disconnecting J7 as this disconnects the horizontal and vertical synchronisation signals that the monitor uses to produce the internal high voltages for the tube. The result is that the horizontal and vertical signals disappear and the electron gun is not deflected (hence the single spot in the centre of the screen) and the high voltages disappear with time because there is no horizontal drive (hence the dot disappears over time).

Possibly yes, the fault is on the main board and not the monitor if the video blanking signals are missing. This would (however) be a strange (and highly improbable) but not impossible fault.

Yes, B+ is the boost voltage. The numbers in parenthesis (according to note 5 of the monitor schematic) are for the 'DOK' version (whatever that is?)

Dave

Don't know what DOK means either. On the flyback is a number printed : 902475-03 but no manufacturer.

I'm a bit scared to measure the boostvoltage. All of the components are in the back of the monitor and very difficult to reach. I will try and see if I can make a connection with the correct components (like coil L2 or SG2) from the underside of the pcb to see what voltage is on this coil. Maybe soldering a 2 wires over SG2 and then to my voltmeter (Fluke)

What should the voltage be? 85V or 95V

BertZonn
February 26th, 2017, 12:59 PM
Don't know what DOK means either. On the flyback is a number printed : 902475-03 but no manufacturer.

I'm a bit scared to measure the boostvoltage. All of the components are in the back of the monitor and very difficult to reach. I will try and see if I can make a connection with the correct components (like coil L2 or SG2) from the underside of the pcb to see what voltage is on this coil. Maybe soldering a 2 wires over SG2 and then to my voltmeter (Fluke)

What should the voltage be? 85V or 95V

My mistake!!! :oops: :oops: :oops:

I think I have the DOK version because of the number printed on it. So it must be 85V DC.
I will see if I can measure the voltage tomorrow. It's a bit late her in Belgium (almost 11 PM)

daver2
February 26th, 2017, 01:01 PM
Yep, soldering 2 temporary wires is the way to go. Keep your fingers well out of the way! Also don't forget that this voltage may still be there after you have switched the monitor off.

Since we don't know what DOK stands for we don't know whether the voltage should be 85V or 95V...

It certainly shouldn't be higher than (say) 100V.

Let's take a measurement and then make an engineering judgement as to whether this looks right or not.

EDIT: Ah - so you have worked it out. Well done! Yep, late in the UK as well - but not quite as late as in Belgium (10 PM). You certainly don't want to be measuring high voltages when you are tired!

Dave

BertZonn
February 26th, 2017, 01:17 PM
Well Dave, let's hope we'll find THE solution to this problem. First of all I think we must determine where the fault comes from. Is it the monitor or is it the mainboard?
I don't care if I must buy a handfull of 74** chips and replace some of them. I've done that before on other equipment. I will place the new chips in sockets.
Ok, bye for now. A new day tomorrow.

Bert

KC9UDX
February 26th, 2017, 01:21 PM
If your brightness pot works, which you indicate that it does, you can use it to isolate the problem to either the monitor or PET logic board.

If turning the brightness control all the way down doesn't cause the screen to go completely black, you certainly have a problem inside the monitor.

BertZonn
February 27th, 2017, 10:11 AM
I have measured the voltage after L2 where it says in the schematics: +95V BOOST (+85 VOLT BOOST)
I have the DOK version of the flyback so +85 Volt would be correct in my monitor.

The voltage is 82,2 Volt DC so that is within range I gues.

BertZonn
February 27th, 2017, 11:03 AM
If your brightness pot works, which you indicate that it does, you can use it to isolate the problem to either the monitor or PET logic board.

If turning the brightness control all the way down doesn't cause the screen to go completely black, you certainly have a problem inside the monitor.

When I turn the knob counterclockwise the text is very dim and visible but the lines are bright. When I turn the knob clockwise the text is getting brighter but the lines too.
The screen doesn't go completely black. The picture is taken at the lowest brightness setting.
36623

BertZonn
February 27th, 2017, 11:06 AM
I made a movie starting with the lowest possible setting of the brightness control, then turning is to the highest position and back again.

http://vid794.photobucket.com/albums/yy226/bertzonn/PET2_zpssfqm0ecw.mp4

KC9UDX
February 27th, 2017, 11:54 AM
I can't see the movie from here, but my long distance diagnosis is thus

1) CRT grid #1 (control grid) isn't negative enough
and/or
2) CRT grid #2 (screen) is too positive
and/or
3) The CRT is defective, and grid #3 (suppressor) link is broken
and possibly
4) The PET isn't performing retrace blanking.

I'd start at #1 and work my way down. Be very careful measuring with the power on, or, attach remote leads like you did earlier. In any case, be careful, you're measuring relatively high voltage here. Make your measurements relative to the CRT cathode. Measure grid 1 DC voltage and tell us what you get. It should be significantly negative, but I don't know how much without the service data, which I think you have. If that checks okay, go to grid 2. You'll need a specification for that too. If both those are valid, you probably have a defective tube. Don't worry about the PET board yet.

If either grids 1 or 2 are incorrect, you can work your way backward from there.

BertZonn
February 27th, 2017, 12:28 PM
I can't see the movie from here, but my long distance diagnosis is thus

1) CRT grid #1 (control grid) isn't negative enough
and/or
2) CRT grid #2 (screen) is too positive
and/or
3) The CRT is defective, and grid #3 (suppressor) link is broken
and possibly
4) The PET isn't performing retrace blanking.

I'd start at #1 and work my way down. Be very careful measuring with the power on, or, attach remote leads like you did earlier. In any case, be careful, you're measuring relatively high voltage here. Make your measurements relative to the CRT cathode. Measure grid 1 DC voltage and tell us what you get. It should be significantly negative, but I don't know how much without the service data, which I think you have. If that checks okay, go to grid 2. You'll need a specification for that too. If both those are valid, you probably have a defective tube. Don't worry about the PET board yet.

If either grids 1 or 2 are incorrect, you can work your way backward from there.

I would like to know what grid #1 is. I suppose you mean G1 on the CRT in the schematics. The same for grid #2, that would be G2 then. Correct me if I'm wrong!

Point 1: I think that grid #1 is for the brightness then. Voltage should be -30V. I measured a voltage of -35,4V. On the wiper (of R9) the voltage varied between 0V and -35,4V so in my opinion this is a correct voltage.

Point 2: grid #2. The boost voltage should be 85V but it is 82,2V. That is only 2,8V difference. Could that cause the problem?

Point 3: grid #3. Can't find that one in the schematics. Only G1, G2 and G4. The CRT produces an image so I'm not sure the CRT is defective.

Point 4: The PET could have some damaged IC's. Like I said before someone has replaced the 3 voltage regulators on the mainboard but I don't know why. Were they blown because someone connected the PET to 230V directly?

I can measure voltages on the CRT itself. I can track the wires from the tube back to the pcb and make a temporary connection on the PCB with the monitor/PET switched off.
The CRT has the following connections on the back: E1, E2, E3 (should have 12V DC), E4 (ground), G1, G2 and G4
I will try to measure these voltages tomorrow evening.

BertZonn
February 27th, 2017, 12:43 PM
Just made an appointment with that technician in Brussels I spoke of. I will go and see him on saturday afternoon.
He has another PET (working) so we can exchange mainboards and monitors.
That way we can determine where the fault is, monitor or mainboard.

KC9UDX
February 27th, 2017, 12:51 PM
G3 is connected to K internally in the tube. If this connection is broken, the result could be exactly what you are experiencing.

Do measure right at the CRT, and before you start it may be a good idea to unplug the CRT and clean the pins and socket. It's very important to measure from the grids to the cathode (K), not ground. The cathode may be at ground potential, or it may be positive to ground.

Grid 1 is (probably) where the signal from the PET goes. But the way tubes work, it must be biased negative with respect to the cathode, else that can cause what you are seeing.

I'm not familiar with the PET monitor, and some monitors are different than others. But if you are getting the correct bias on the grids, the monitor will work.

I don't know if G4 is a focusing anode , accelerating anode, or additional control grid. But it should have a proper value in the service documentation, too.

There's nothing in the bottom half of the chassis (PET board) that can cause the issue you are having with minimum brightness. You should be able to get a completely black screen via the brightness knob, even if the PET is trying to display a completely "white" screen, or if it's acting completely wrong altogether.

At this point, it seems to me that the PET is doing what it's supposed to. But we'll know for sure when we know the top half (monitor) is doing what it should, which as of now it is not.

AndyG
March 2nd, 2017, 05:58 AM
PM me after you discussion the technician in Brussels. I do have a spare 9inch CRT and recapped board (know works) if you cannot find spares.

BertZonn
March 4th, 2017, 08:41 AM
PROBLEM SOLVED!!!!!

I arrived this afternoon in Brussels. The first thing we did was connecting my PET to his monitor and there was a beautiful picture of a correct working monitor. So the problem was in my monitor. Then we exchanged the tubes. My PCB with his tube and vice versa. His PCB with my tube was working perfect so we narrowed it down to my PCB. Then we exchanged te flyback and the problem was still there so the flyback was not the cause. Lucky me!!
We tested the remaining transistors that I did NOT replace but they were all in perfect condition. Then we removed the PCB and held the 2 PCB's next to each other and he starten measuring resistances on both PCB's. We found a short circuit is C4 so the 33V zener was also shortened. There was a second capacitor (C16) that was also out of range so we changed that one too.

We mounted my PCB in my monitor with my CRT and hooked it up to my PET and everything was OK!!! I'm a happy man!!
36722 36723

I wish to thank everybody here for their efforts and thinking with me.
A special thanks goes to the man in Brussels, Stéphane. He did all the measuring and soldering and he spent more than 3 hours trying to find the error.
Thank you all!!!!

daver2
March 4th, 2017, 10:26 AM
Well done, nice to see the dark background at long last!

Looking at the schematic I am surprised we didn't measure the 33V on CR7... but then hindsight is a wonderful thing!

Thanks for posting the 'fix' to help out others in the future.

Dave

BertZonn
March 4th, 2017, 12:17 PM
Well done, nice to see the dark background at long last!

Looking at the schematic I am surprised we didn't measure the 33V on CR7... but then hindsight is a wonderful thing!

Thanks for posting the 'fix' to help out others in the future.

Dave

Sure, why not? If I can help somebody else I will, just the way I was helped here. Hopefully is it the same solution for Simplex.

Bish500
March 4th, 2017, 05:44 PM
Congratulations! I'm happy to see you were able to fix it!

karateed
March 15th, 2017, 09:00 AM
Hi Bert,

When I moved to Iceland in 1980, I had a transformer and a 120V-60Hz PET. There were absolutely no issues or noticeable differences between 50 and 60 Hz. I used that computer for 4 years while there and finally ended up with a BBC B Micro for about a year before moving back to Canada. That's actually my main retro computer now but recently I went and fixed the 'sticky' keyboard problem. It involved taking the keyboard apart and cleaning all the contacts. All the keys work fine now except the up/down cursor key so I'll take it apart again and check that one out. At any rate, you should be fine with your new/old PET. Enjoy it, they are still a ton of fun.

Ed...... :-)

BertZonn
March 16th, 2017, 02:14 PM
Hi Bert,

When I moved to Iceland in 1980, I had a transformer and a 120V-60Hz PET. There were absolutely no issues or noticeable differences between 50 and 60 Hz. I used that computer for 4 years while there and finally ended up with a BBC B Micro for about a year before moving back to Canada. That's actually my main retro computer now but recently I went and fixed the 'sticky' keyboard problem. It involved taking the keyboard apart and cleaning all the contacts. All the keys work fine now except the up/down cursor key so I'll take it apart again and check that one out. At any rate, you should be fine with your new/old PET. Enjoy it, they are still a ton of fun.

Ed...... :-)

Hi Ed,

My PET is in perfect working condition right now. The monitor has been repaired and the computer works great. I use a step-down transformer to go from 230V to 115V and this works just fine. The monitor is a bit unstable but that is not a problem. The characters are dancing a bit but then just a little bit.

At the moment I'm trying to transfer programs from my computer to the PET. I'm playing with the .tap files and I'm copying these files to tape using the 'audiotap' program. I'm tryin to figure out at what level I must copy the audio to the tapes. At this moment I'm using a Sony mini Hifi set with a tape drive connected to the audio-out of my computer but I'm afraid this unit has an automatic recording level for the tapes.
Some programs are recognized by the PET and others are not. I bought another tapedeck (Pioneer CT-339) that will arrive some day next week. Hopefully than I can copy the programs I have to tape at the correct level.
In the future I want to buy a floppy disk drive (8050) or a SD card drive from tynemouthsoftware.co.uk.

Bert

karateed
March 17th, 2017, 06:58 AM
Hi Bert,

That's really good. I'm wondering about the 'dancing' characters. That shouldn't be happening. When I had my PET in Iceland it was rock solid. I don't remember how big the transformer was but it was pretty heavy. I dropped it once on a really expensive carpet and it took quite a chunk out of it so it was pretty heavy duty. I expect for the machine you have, the draw would be even more than my PET so probably needs a pretty skookum TF. Some of the experts on here may be able to say exactly what should work.

I've only barely skimmed how to get programs to my PET from online sources but I think I'll need a 'disk' solution of some sort. I've looked a bit at 8050s but that seems to be a crap shoot at the moment. Most of them are 'untested' or repair only. The odd one that I've found is fairly expensive and there's still no guarantee that they are working even though they say tested and working. I've been bit by that bug before.

I'm also probably looking at the tynemouthsoftware solution as I've tried to get the PETDisk solution to no avail. I'm not sure if he's stopped making them or something's happened to the man but I understand there are projects underway to recreate the hardware by some groups.

For the cassette, I understand it needs a lower setting volume wise to work well on the PET. I guess higher volumes tend to 'distort' the signal.

I also have a BBC Micro and with that it wants a louder signal but it seems the PET is the opposite for a clear signal.... wouldn't have thought that from my experiences but after watching the 8-bit Commodore wars, it was clear that other than the Commodore tape decks, it was a crap shoot for the PET to recognize a signal from another source. I suspect that's what you're running into.

I followed this thread from beginning to end and it's really a fun read. I'm no expert at electronics but I could follow along with what was done quite well. That speaks to the obvious expertise and patience of the people here, nice job.

Ed...... :-)

BertZonn
March 17th, 2017, 02:35 PM
Well Ed, I'm no expert too. I know quite a bit of electronics but not everything. I've had electronics at school in the '70-'80 so that is a long time ago.
Today I received my cassettedeck, Pioneer CT-339, and I've tried some settings. First it was too loud or too soft but now I've found a setting that works.
Main output to the speakers at 75%, output of Windows Media Player at 100% and then recording on the Pioneer at 0 dB. Most programs will load into the PET.
After a correct load I save the programs to another tape with the PET. This seems to work.
Now I'm searching for nice programs for my PET but there are not so many websites that have the .TAP files.
I see a lot of .PRG files but now I must figure out how to get these .PRG files to tape. I love this hobby!!!

I wonder if it is possible to connect a standard cassettedeck to the PET of maybe even the line-out from my laptop and simulate the Commodore Datasette recorder. Maybe a little switch to simulate the play button.
I must dive into this. I'm not sure about the signal coming from the datasette. Is it a 5Volt signal or less.

Bert

karateed
March 17th, 2017, 02:57 PM
Hi Bert,

I've done a bit of a search for schematics and found this site - http://www.commodore.ca/manuals/pet_schem_display_rom_ram/pet_schematics.htm There are schematics for the datasette tapedeck that should give you the information you need to use a normal tape deck with the pet. I'm fortunate to have my PET cassette machine. I've just ordered the SD disk solution from TyneMouthSoftware so once that happens, I can archive/store my tape programs. I've got a lot of cleanup to do on my PET. I took a good look at the motherboard and mice could live on it, it's so dirty. It's been sitting for about 2 years. I played with it for a while at that time and also cleaned it but..... it needs love and care so I'll be doing that soon.

Hopefully the schematic will help you find what you need. I haven't looked seriously at it yet but perhaps I can see what it's doing too though it's been a very long time since I worked of a schematic so it'll be a challenge.

I can see you learn fast from the 31 page thread on fixing your PET, that's a good thing in this hobby.......

Ed...... :-)

MikeS
March 17th, 2017, 06:53 PM
I see a lot of .PRG files but now I must figure out how to get these .PRG files to tape. I love this hobby!!!
Google 'prg to tap file'


I wonder if it is possible to connect a standard cassettedeck to the PET of maybe even the line-out from my laptop and simulate the Commodore Datasette recorder. Maybe a little switch to simulate the play button.
I must dive into this. I'm not sure about the signal coming from the datasette. Is it a 5Volt signal or less.

There are fairly simple (one IC) circuits out there to convert the audio from a 'normal' cassette deck to the digital signal that the PET expects.
Here's one, but there are simpler ones that work.
http://www.zimmers.net/anonftp/pub/cbm/documents/projects/interfaces/index.html

BertZonn
February 22nd, 2018, 02:45 PM
I'll try to blow new life in an old thread. ;)
Got 2 Commodore machines last week. A 2001-8C and a 4016
The 2001-8C (nice little keyboard and a black screen with white letters) has a problem with the datasette. I will not read or write to tape. When I save a program I can see that a signal is send to the head (on my scope) but nothing is recorded. When I play (Load) from tape it wil not load anything. I'm afraid the head is gone. It is not an open circuit and no shortcut. I messured about 160 ohm on the connectors. I will try to find another recording/playback head.

The 4016 works fine but when I load Space Invaders I get the screen about the sound option and then in freezes. Is the 4016 not compatible with Space Invaders?
43931

AndyG
February 23rd, 2018, 11:02 AM
Not an expert on the tape machines but have often read that they benefit from a new belt..... to fix read/write issues.



Are you playing the basic 4 version or basic 2 ?

I suspect you maybe loading the version for basic 2.


I'll try to blow new life in an old thread. ;)


The 4016 works fine but when I load Space Invaders I get the screen about the sound option and then in freezes. Is the 4016 not compatible with Space Invaders?
43931

BertZonn
March 4th, 2018, 12:40 AM
I'm not sure. I found Space Invaders on the internet as a TAP file. The 4016 runs with Basic 4 and the 2001-8C with basic 2 I guess.
It runs on the 2001 but not on the 4016.

The original tapedrive on the 2001 has a problem. I think the recording/playbackhead is defective. Why? I can't load a program from tape. It keeps on searching.
When I give the 'save' command the computer wants to write the header of the program to the tape. I connected a small scope to de connections of the head and I could see that a signal is send to the head.
When I play the tape on a Pioneer cassettedeck I hear no sound at all so the electrical signal is not transformed to a magnetic signal for the tape.
When I record a program from a TAP-file to the tape using the Pioneer cassettedeck, I can load the game into the 2001 and the 4016 with a seperate (other) tapedrive I have but with the original datasette it will not load.

Can I use any tapedrive head to replace the head of the datasette?

BTW, the belt on the old datasette was replaced so that is not the problem.