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View Full Version : Please help me revive a Pet 2001!



minty
September 4th, 2014, 06:40 AM
Hi all! I hope you can help me.

I thought I should try and revive my beloved 2001. It's been a talking point in my office for ever, but it hasn't been turned on for over 10 years - last time I tried it appeared to be dead, and fear of electrocuting myself by touching the wrong part of the CRT has meant it's mothballed ever since.

Well, today I changed the fuse, plugged her in - and, oh my god, the screen lit up! I was expecting a big bang and smoke. So now I'm sitting here looking at a screen of gibberish (see picture), and I'm wondering what to do next - can anyone help?

I'm not a hardware person, and my only diagnostic tool is a multimeter, but I'd love to get it working again! It's got a nice clear, sharp screen, and gibberish gives me hope there's something alive in there.

Many thanks in advance,

Tony
20278

MikeS
September 4th, 2014, 08:08 AM
The first thing is to rotate it upright; they don't like to work on their side ;-)

No fear of electrocuting yourself unless you take the cover off the back of the monitor.

Undo the two screws if necessary and lift up the 'hood' ('bonnet' if you're in the UK), prop it up and tell us what the assembly number is (along the right edge near the front).

You might try (with power off) pushing down on all the socketed chips (not too hard) to make sure they're properly seated, and pushing them back and forth (along the long axis) in their socket to break any oxidation.

With a little luck that'll do it.

Good luck.

BTW, please put your location in your profile.

mike

minty
September 4th, 2014, 11:33 AM
Hi! Location set (hello from Cambridge, England), computer turned the right way up! (no idea why it got turned, I'll watch out for that in the future).

So ... I opened her up, and blimey, it's filthy in there - see attached. I pushed down on all the socketed chips, turned it on, and wow, she lives again! I wish I'd known it would be this easy years ago - these things are built like tanks!

I do have a couple question I hope you all can help me with:

1. Should I resist the temptation to clean the motherboard? It's working, and I'd like to keep it that way, but I wonder if that might be better in the long run.
2. All the 2001s I see online have black cassette drives, but mine is beige, and a slightly different design. Is this something that was replaced later in its life, or did it come like this?
3. I'd like work out how old this computer is - what should I look for to help me date it?
4. I'd love to load some software onto it, but I don't think I can produce a tape (and I'd be surprised if the tape drive still works). Can I use an external sound source?

Many many thanks in advance!
20284

dave_m
September 4th, 2014, 12:39 PM
1. Should I resist the temptation to clean the motherboard? It's working, and I'd like to keep it that way, but I wonder if that might be better in the long run.


A little cleaning is OK, but don't use water. Water vapor is the enemy of printed wiring boards. Can you get some very pure isopropyl alcohol? Unfortunately many like to put their board in the dishwasher and the boards will come out looking beautiful. But ask an Electronics Reliability Engineer and he would say that unless you put the board quickly afterwards into a thermal-vaccuum station for 20 hours of high heat and high vacuum to dry and outgas the water vapor and contaminants, you just took years of life off the board.

Also perhaps you should not use high pressure air to blow out the board as it create thousands of Volts of static electricity. If the ICs were soldered into a board with an internal copper ground plane, it would easily handle it as the large area of the plane would dissipate the static voltage, but I just found out the Commodore main board does not have a ground plane.

MikeS
September 4th, 2014, 01:17 PM
Hello Tony; welcome and congratulations! You are now a qualified PET technician ;-)

I'm not quite as anal as Dave about compressed air so if it's just dusty I'd blow out the dust with compressed air or the outlet of a vacuum cleaner, assisted with a stiff brush. Standard procedure both in my hobby and also professionally (But I assume no responsibility).

There were at least three different internal tape drives used in the PET and yours is one of the two later ones. It's hard to date PETs accurately, but your best bet would probably be the date codes on the ICs; beside the 74xxx and 65xx numbers you'll probably find at least one other four or five digit number probably starting with two digits in the 76 to 78 range and the latest one of those would be close to the week in which it was manufactured. Any number higher than 78 or 79 probably means that the chip was replaced, although you'd likely see evidence of it being resoldered. Of course the serial number would give you a relative indication.

That looks like the 320008 board; is it? Also, tell us at least one or two of the numbers on the 24-pin ROM chips in row H; different revisions of BASIC had different issues.

Try typing in a little program, saving it to the cassette and loading it back in; you never know...

Unfortunately, without spending a little money there's no easy way to load in a program other than typing it or getting a tape from someone. Also, whether you can use a disk drive or one of the modern solid state emulators depends on the ROM version (see above).

dave_m
September 4th, 2014, 01:43 PM
Hello Tony; welcome and congratulations! You are now a qualified PET technician ;-)

I agree. Anybody that posts on the Commodore Forum would have been offered a job at Commodore as a top gun designer. :)



I'm not quite as anal as Dave about compressed air ...

Well thanks for the complement, Mike. Everyone knows that all good engineers have strict anal personalities! ;)

dave_m
September 5th, 2014, 11:16 AM
4. I'd love to load some software onto it, but I don't think I can produce a tape (and I'd be surprised if the tape drive still works). Can I use an external sound source?



A member of this forum tezza has done a lot of work on creating cassette files for the PET. I found this link which may get you started. I'm sure somewhere he has written more about this. It uses things like TAP and WAV files and the VICE PET Emulator that runs on a PC.

http://www.classic-computers.org.nz/blog/2011-02-27-pet-programs-for-download.htm

MikeS
September 5th, 2014, 11:56 AM
A member of this forum tezza has done a lot of work on creating cassette files for the PET. I found this link which may get you started. I'm sure somewhere he has written more about this. It uses things like TAP and WAV files and the VICE PET Emulator that runs on a PC.

http://www.classic-computers.org.nz/blog/2011-02-27-pet-programs-for-download.htmHmm... It looks like Tez doesn't actually say that he created a working cassette without going through a C64; the thing that complicates the issue a bit on commodore machines is that the tape drive is (sort-of) digital.

But I'd give it a try; I do seem to recall duplicating PET tapes with 'normal' audio equipment so it oughta work once you get the levels etc. right.