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falter
December 6th, 2013, 04:14 PM
Got a PET 4016 I bought off ebay for $60.

So far so good.. she's a bit rusty in places but everything works -- except it seems to have its characters all mixed up, as in the photograph.

16253

If I type, it produces characters. So I think what I'm looking at is a garbled version of the Basic screen and prompt. I was thinking this must have something to do with the character generator.. however the working one in my PET 2001-8 doesn't fit and I'm a bit reluctant to mess with the working 2001-16 I have. Am I on the right track here? Other possibility I'm thinking would be video RAM.. but these are soldered in.. not sure if I could pull off a repair, or do that 'stacking RAM' trick where you take socketed RAM from another pet and place it on top of the legs of the suspect RAM? Don't know if those are compatible all the way back to my 8 or not.

Advice appreciated!!

falter
December 6th, 2013, 05:16 PM
Swapped character generators with my 2001-16 but no difference in behavior.. and confirmed the char generator from the 4016 worked in the 2001-16. Video RAM maybe? It's odd because it appears to be simple character substitution -- each time I type something in and hit enter, I get the exact same prompt, what I assume is 'READY' but with weird characters instead..

giobbi
December 6th, 2013, 06:16 PM
Video RAM maybe?

Maybe. I had the same problem in the past (or at least a very similar one); I'm almost sure it happened with my chiclet PET and it was a broken video RAM chip, but I'm not 100% sure :-(
So I tried right now to remove the Video RAM chips from my 8032 (actually the only PET I have here on my desk); I can't reproduce your same pattern, but I had char substitution (and some chess table pattern). The 8032 has 4 x 2114, yours should have just two, if I'm right. Have you a couple of 2114 to try at least a piggyback?

--Giovi

falter
December 6th, 2013, 06:37 PM
Maybe. I had the same problem in the past (or at least a very similar one); I'm almost sure it happened with my chiclet PET and it was a broken video RAM chip, but I'm not 100% sure :-(
So I tried right now to remove the Video RAM chips from my 8032 (actually the only PET I have here on my desk); I can't reproduce your same pattern, but I had char substitution (and some chess table pattern). The 8032 has 4 x 2114, yours should have just two, if I'm right. Have you a couple of 2114 to try at least a piggyback?

--Giovi

Unfortunately no.. I'll have to see if I can find some. However, after removing, cleaning and re-socketing all chips, I got a different screen -- this time solid green. The ROM in UD8 had a couple of slightly rusty legs. It was after I cleaned and replaced that one that we got the green screen. SO now I'm thinking it's the BASIC ROMs. I realized that no matter what I entered, it always came back with that same 5-7 character prompt.. so it occurred to me that it might not actually be interpreting anything properly.

I wonder though how I could clean those sockets..

falter
December 6th, 2013, 07:05 PM
Maybe. I had the same problem in the past (or at least a very similar one); I'm almost sure it happened with my chiclet PET and it was a broken video RAM chip, but I'm not 100% sure :-(
So I tried right now to remove the Video RAM chips from my 8032 (actually the only PET I have here on my desk); I can't reproduce your same pattern, but I had char substitution (and some chess table pattern). The 8032 has 4 x 2114, yours should have just two, if I'm right. Have you a couple of 2114 to try at least a piggyback?

--Giovi

Unfortunately no.. I'll have to see if I can find some. However, after removing, cleaning and re-socketing all chips, I got a different screen -- this time solid green. The ROM in UD8 had a couple of slightly rusty legs. It was after I cleaned and replaced that one that we got the green screen. SO now I'm thinking it's the BASIC ROMs. I realized that no matter what I entered, it always came back with that same 5-7 character prompt.. so it occurred to me that it might not actually be interpreting anything properly.

I wonder though how I could clean those sockets..

giobbi
December 7th, 2013, 03:15 AM
Unfortunately no.. I'll have to see if I can find some. However, after removing, cleaning and re-socketing all chips, I got a different screen -- this time solid green. The ROM in UD8 had a couple of slightly rusty legs. It was after I cleaned and replaced that one that we got the green screen. SO now I'm thinking it's the BASIC ROMs. I realized that no matter what I entered, it always came back with that same 5-7 character prompt.. so it occurred to me that it might not actually be interpreting anything properly.

I wonder though how I could clean those sockets..

It seems (to me) a char ROM related problem. Since you're sure the ROM itself is ok, I wish to suggest you to replace the char ROM socket with a fresh one. I had *many* issues due to rusty sockets. Really, many! In example, in my latest fix, my chiclet PET, I had to replace the char ROM socket (faulty) and all the other ROM sockets; there was at least one faulty, but I decided to change all of them to prevent any other issue in the future.

Replacing a socket is quite easy; you can carefully remove the plastic housing pulling it out of the pins with a screwdriver between the housing and the PCB (but beware not to cut the traces!). Then you can remove the pins one at time.

2114 are still easy to find on eBay; i.e.: http://www.ebay.it/itm/220933703741?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649

--Giovi

falter
December 7th, 2013, 01:02 PM
Here's a video of the 4016 in action for those curious. I did a fairly thorough cleaning with electrical cleaner and a small fine but firm brush. That got me back to where I started. I suspect it's a ROM issue.. either with the ROMs themselves or the socket.. not sure because the 2001-16's ROMs are slightly different and don't appear to work in this unit. In the last seconds of the video if you look closely you can see certain characters 'flickering', like the machine is trying to do something but can't.

I'm not even sure if all the ROMs are in their correct sockets.. 30+ years of fiddling around might have some in the wrong place potentially.. need to find a photo or schematic.

http://www.youtube.com/watch?v=QCZjkibplUo

falter
December 7th, 2013, 02:30 PM
Another interesting thing (don't know if it's relevant or not) -- the PET responds to certain keypresses ok -- like CLR HOME will clear the screen (albeit the screen is solid green), some of the keys pressed line up with the characters they can shift into. Cursor keys work also..

SomeGuy
December 7th, 2013, 02:59 PM
At least you have something you can diagnose here. Better than a system that sits there like a lump on a log, where the problem could be anything.

I wouldn't rule out the possibility of a part failing in such a way that it always sets a data bit high or low, making it look like a bad connection. Testing the top of the chip against the bottom of the board with a volt-ohm meter might reveal a bad connection. In this case a logic probe could probably reveal if a data line - probably on a video memory data line - is stuck.

dave_m
December 7th, 2013, 07:46 PM
In this case a logic probe could probably reveal if a data line - probably on a video memory data line - is stuck.

Yes, I agree, it seems like some video RAM bits are stuck high. A stuck SD7 would give you the inverse video you are seeing and other bits would cause the graphics characters instead of text. When you get a 2114 RAM chip, see if piggybacking causes a change.

MikeS
December 7th, 2013, 08:27 PM
Yes, I agree, it seems like some video RAM bits are stuck high. A stuck SD7 would give you the inverse video you are seeing and other bits would cause the graphics characters instead of text. When you get a 2114 RAM chip, see if piggybacking causes a change.Hmmm... can a bad video RAM chip actually cause it to display graphic characters? Have you tried swapping the 6522 VIA and/or checking its socket and related connections (and those of the character generator)? Maybe try lifting pin 19 of the CG ROM and alternately connecting it to GND and 5V Vcc and see what happens?

I'm confused; you're talking about a 4016 and a 2001-16; aren't they essentially the same, with maybe just a different ROM set? Got some part numbers and pictures of the main boards and maybe the ROM numbers and locations?

falter
December 7th, 2013, 09:23 PM
Hmmm... can a bad video RAM chip actually cause it to display graphic characters? Have you tried swapping the 6522 VIA and/or checking its socket and related connections (and those of the character generator)? Maybe try lifting pin 19 of the CG ROM and alternately connecting it to GND and 5V Vcc and see what happens?

I'm confused; you're talking about a 4016 and a 2001-16; aren't they essentially the same, with maybe just a different ROM set? Got some part numbers and pictures of the main boards and maybe the ROM numbers and locations?

I haven't tried swapping the 6522.. I did pull it along with all the roms, one by one, just to see how the system behavior changed. It doesn't react to the 6522 not being there at all. But I didn't think to borrow one from the 16.

I thought the 4016 and the 2001-16 were basically the same unit too. The main ROM numbers appear to be the same, but the numbers after the dash are different. When I tried swapping a couple.. The machine wouldn't do anything.. Not even the little bit in the video. I assumed the dash numbers indicated a different revision and figured they must not be compatible.

MikeS
December 7th, 2013, 09:43 PM
I haven't tried swapping the 6522.. I did pull it along with all the roms, one by one, just to see how the system behavior changed. It doesn't react to the 6522 not being there at all. But I didn't think to borrow one from the 16.

I thought the 4016 and the 2001-16 were basically the same unit too. The main ROM numbers appear to be the same, but the numbers after the dash are different. When I tried swapping a couple.. The machine wouldn't do anything.. Not even the little bit in the video. I assumed the dash numbers indicated a different revision and figured they must not be compatible.They should be compatible if you swap the entire set. Doesn't the 4016 have one more than the 2001-16? Again, what are the numbers and locations?

jac_goudsmit
December 7th, 2013, 10:14 PM
It could just be that the 74LS257 (74257?) that switches the high 4 bits of video memory between the 6502 and the video hardware, is stuck with all 4 outputs on...

===Jac

MikeS
December 7th, 2013, 10:58 PM
It could just be that the 74LS257 (74257?) that switches the high 4 bits of video memory between the 6502 and the video hardware, is stuck with all 4 outputs on...

===JacYou have a point, although I'm not sure you'd need all 4 to be stuck; if the Graphic line were stuck that would only affect the shifted characters.

Might still be worth while to lift pin 19 though; that might put it in lower case mode.

dave_m
December 8th, 2013, 06:39 AM
Have you tried swapping the 6522 VIA and/or checking its socket and related connections (and those of the character generator)?

Mike,
I agree that one of the stuck bits might be the the 'Graphics' signal which may imply that the 6522 or its connections is bad.

falter
December 8th, 2013, 01:16 PM
Mike,
I agree that one of the stuck bits might be the the 'Graphics' signal which may imply that the 6522 or its connections is bad.

I've confirmed the 6522 chip itself is ok.. tested good in the 2001-16.

Here are photos of both motherboards (hopefully the chip numbers are visible with whatever the forum does to shrink them, if it does):

1626316264

You'll note on the 4016 (with the way dirtier motherboard) it has an extra 'Palo Alto' chip. The 2001 has a non-MOS chip in UD5.

So would the next step be, take the entire ROM set out of the 2001 and put it in the 4016 and see what happens?

Just in case the pics aren't clear enough.. on the 2001-16 I have:

UD5 - 8009E C48179 T2590
UD6 - MOS 901465-01 (?)
UD7 - MOS 901465-02
UD8 - MOS 901447-24
UD9 - MOS 901465-03

Then in the 4016:

UD4 - 8145 C68160 TC49BX (palo alto)
UD5 - 901465-23
UD6 - 901465-20
UD7 - 901465-21 (I think.. last number is almost illegible)
UD8 - 901447-29
UD9 - 901465-22

MikeS
December 8th, 2013, 01:51 PM
ROM numbers look fine; looks like they both have an optional ROM in addition to the standard set; you might want to temporarily remove those (2001-16:UD5, 4016:UD4) in the unlikely case that they're causing problems.

It does indeed look like a problem with the upper video RAM or associated circuitry. Carefully try briefly grounding pin 12 of IC F7 (2114) and see what happens. No insult intended but we've learned to not assume anything: you do know how the IC pins are numbered?

giobbi
December 8th, 2013, 01:52 PM
I'm confused; you're talking about a 4016 and a 2001-16; aren't they essentially the same, with maybe just a different ROM set? Got some part numbers and pictures of the main boards and maybe the ROM numbers and locations?

I believe that 2001-16 was also known as 3016, no CRTC system; while the 4016 (like the 4032, 8032, etc.) are CRTC based.
Both can use the basic 4 romset (maybe changing the edit ROM only, I think)... hoping I'm not going wrong...

--Giovi

MikeS
December 8th, 2013, 02:00 PM
I believe that 2001-16 was also known as 3016, no CRTC system; while the 4016 (like the 4032, 8032, etc.) are CRTC based.
Both can use the basic 4 romset (maybe changing the edit ROM only, I think)... hoping I'm not going wrong...

--GioviConfusing, I know, but I believe they are all basically the same; there was a lot of variation in model numbers but AFAIK the 3016 is generally what the 2001-16 was called in Europe while the 4016 was the same computer with BASIC 4 ROMs; there may also have been a 4032 with a 9" screen and no CRTC but the 12" 4032 version with CRTC is usually referred to as the "FAT 40".

But you're right about the ROMs; AFAIK the BASIC 4 ROMs are the same in all the 'normal' PET/CBM machines except for the 'E' edit ROM.

falter
December 8th, 2013, 02:23 PM
ROM numbers look fine; looks like they both have an optional ROM in addition to the standard set; you might want to temporarily remove those (2001-16:UD5, 4016:UD4) in the unlikely case that they're causing problems.

It does indeed look like a problem with the upper video RAM or associated circuitry. Carefully try briefly grounding pin 12 of IC F7 (2114) and see what happens. No insult intended but we've learned to not assume anything: you do know how the IC pins are numbered?

What would we see by grounding that pin, just so I know what to look for?

IIRC, ICs are numbered beginning with pin 1 on the left side of the 'notch' (if looking at the chip from above with notch top), then 2, 3, 4, etc down the left side, then onwards up the right side, with the last pin being directly opposite pin 1?

falter
December 8th, 2013, 02:42 PM
http://www.ebay.com/itm/NTE-NTE2114-IC-INTEGRATED-CIRCUIT-MOS-4K-x-1-4K-STATIC-RAM-EQUIV-To-ECG2114-/161062609043?pt=LH_DefaultDomain_0&hash=item2580146093#ht_281wt_1124

This is what I'd be looking for for replacement 2114s right?

Also -- would I be able to take the ROMs from my 4016 and put them into my 2001-8 to see a) if they work properly there and b) if that tells me any more about the condition of my 8's motherboard and chips? I've swapped RAM around like crazy on the -8 with no change in behavior.. curious if swapping the ROMs out makes it live.

MikeS
December 8th, 2013, 02:45 PM
What would we see by grounding that pin, just so I know what to look for?A normal boot prompt.


IIRC, ICs are numbered beginning with pin 1 on the left side of the 'notch' (if looking at the chip from above with notch top), then 2, 3, 4, etc down the left side, then onwards up the right side, with the last pin being directly opposite pin 1?Yup; counterclockwise, starting and ending beside the notch (when looked at from above).

MikeS
December 8th, 2013, 02:48 PM
http://www.ebay.com/itm/NTE-NTE2114-IC-INTEGRATED-CIRCUIT-MOS-4K-x-1-4K-STATIC-RAM-EQUIV-To-ECG2114-/161062609043?pt=LH_DefaultDomain_0&hash=item2580146093#ht_281wt_1124

This is what I'd be looking for for replacement 2114s right?Yes, but you'll certainly find them cheaper if you look around a bit; they should be <$3.00 ea. or so...


Also -- would I be able to take the ROMs from my 4016 and put them into my 2001-8 to see a) if they work properly there and b) if that tells me any more about the condition of my 8's motherboard and chips? I've swapped RAM around like crazy on the -8 with no change in behavior.. curious if swapping the ROMs out makes it live.It doesn't look like a ROM issue, so I'd check the video section first; can't hurt though, as long as you don't bend or break any pins, put a chip in backwards, etc. etc. ;-)

falter
December 8th, 2013, 03:08 PM
A normal boot prompt.

Yup; counterclockwise, starting and ending beside the notch (when looked at from above).

Thanks Mike -- so when I do this jumping.. do I do it with the machine already on or find a way to secure a jump wire first and then power up briefly?

MikeS
December 8th, 2013, 03:17 PM
Thanks Mike -- so when I do this jumping.. do I do it with the machine already on or find a way to secure a jump wire first and then power up briefly?I'd connect one end of the jumper to GND (say, pin 8 or 9 of the same IC, F7), turn on the PET and wait for a display, and then briefly touch the other end of the jumper to pin 12.

MikeS
December 8th, 2013, 03:28 PM
Some sources of old ICs:

http://www.arcadecomponents.com/index.html

http://www.bigdaddy-enterprises.com/

falter
December 8th, 2013, 03:48 PM
I'd connect one end of the jumper to GND (say, pin 8 or 9 of the same IC, F7), turn on the PET and wait for a display, and then briefly touch the other end of the jumper to pin 12.

Okay I'll give that a shot..

Chuck(G)
December 8th, 2013, 04:18 PM
By all means, give Anchor Electronics (http://www.anchor-electronics.com/) a call or drop a line to them. One of Silicon Valley's best-kept secrets. They have all sorts of old parts.

falter
December 8th, 2013, 07:18 PM
Okay, I tried grounding to pin 9 on the 2114 and touching pin 12. It did change the display, but not to a normal boot prompt. Basically the 'graphic' characters changed to recognizeable characters like % and $ signs. But that was it.. no BASIC prompt, etc.

falter
December 8th, 2013, 07:38 PM
Here's the screen I got it to with shorting pin 12 on UF7 (got wife's help ;)) You can see we're a good ways there.. the number of characters displayed adds up perfectly to *** COMMODORE BASIC 4.0 *** etc. The asterisks and period after what should be READY are there. Could there be a problem maybe with both chips?

16265

dave_m
December 8th, 2013, 08:56 PM
Here's the screen I got it to with shorting pin 12 on UF7 (got wife's help ;)) You can see we're a good ways there.. the number of characters displayed adds up perfectly to *** COMMODORE BASIC 4.0 *** etc. The asterisks and period after what should be READY are there. Could there be a problem maybe with both chips?

16265
Thanks to Mike's idea of grounding SD6 this gives us more clues. Looking at the PETSCII codes (http://www.google.com/imgres?imgurl=http://home.total.net/~hrothgar/museum/PET2001/PETSCII1.gif&imgrefurl=http://home.total.net/~hrothgar/museum/PET2001/&h=324&w=404&sz=13&tbnid=vyg2EqfpvPOTIM:&tbnh=96&tbnw=120&zoom=1&usg=__qaQ48eUAFHs88t7O_xdhXoBKT-w=&docid=ZG8miUynM_48vM&sa=X&ei=SFalUrvFFoqz2gXBtoFY&ved=0CD8Q9QEwBA), it is clear that the SD5 line is stuck high also. We also know that the SD7 line is stuck high due to everything in inverse video. So perhaps the F7 RAM is bad? Do you have a scope?

falter
December 8th, 2013, 09:17 PM
Thanks to Mike's idea of grounding SD6 this gives us more clues. Looking at the PETSCII codes (http://www.google.com/imgres?imgurl=http://home.total.net/~hrothgar/museum/PET2001/PETSCII1.gif&imgrefurl=http://home.total.net/~hrothgar/museum/PET2001/&h=324&w=404&sz=13&tbnid=vyg2EqfpvPOTIM:&tbnh=96&tbnw=120&zoom=1&usg=__qaQ48eUAFHs88t7O_xdhXoBKT-w=&docid=ZG8miUynM_48vM&sa=X&ei=SFalUrvFFoqz2gXBtoFY&ved=0CD8Q9QEwBA), it is clear that the SD5 line is stuck high also. We also know that the SD7 line is stuck high due to everything in inverse video. So perhaps the F7 RAM is bad? Do you have a scope?

No but I'm investing in one.. any recommendations on make/model?

dave_m
December 9th, 2013, 08:36 AM
No but I'm investing in one.. any recommendations on make/model?

I would buy an affordable used non-plastic Tektronix scope like the model 454 or 465 analog scopes. They have a fairly small footprint on your workbench and can be found for around $125 USD plus shipping. Make sure the model has a bandwidth of at least 60 MHz, comes with probes, and is guaranteed to be in working order with pictures of both traces, etc. Pay extra to have the seller package it properly (foam in place, etc).

The new scopes from the orient are pretty flimsy as are some of the cheaper used Tektronix models from the 90's.

MikeS
December 9th, 2013, 09:32 AM
A scope is certainly nice to have, but we probably don't need one here; looks like just a bad 2114 (they were pretty notorious for failing), although Jac could also be right that it's in the circuitry driving it (much less likely though).

falter
December 9th, 2013, 02:57 PM
A scope is certainly nice to have, but we probably don't need one here; looks like just a bad 2114 (they were pretty notorious for failing), although Jac could also be right that it's in the circuitry driving it (much less likely though).

Well, I have enough vintage stuff here now that is guaranteed to fail at some point -- might as well invest in the tools to fix it.

I'm just looking at those websites you guys were kind enough to pass along... it looks like the 2114 chips I need are '2114-45'. However on the site where that 45 number is explicitly mentioned, it is out of stock. On another site (big daddy), there is "2114/9114 RAM (1K x 4 memory) 18 pin DIP, 450ns" -- is one the same as the other?

MikeS
December 9th, 2013, 05:11 PM
Well, I have enough vintage stuff here now that is guaranteed to fail at some point -- might as well invest in the tools to fix it.

I'm just looking at those websites you guys were kind enough to pass along... it looks like the 2114 chips I need are '2114-45'. However on the site where that 45 number is explicitly mentioned, it is out of stock. On another site (big daddy), there is "2114/9114 RAM (1K x 4 memory) 18 pin DIP, 450ns" -- is one the same as the other?Definitely, get the 'scope; I just meant that you don't have to wait for it to repair the PET.

Yes; the -45 or 450ns is the inverse of the speed and anything faster, i.e. with a lower number, should work just fine. I doubt that you'll find anything slower than 450ns, so I'd imagine that pretty well any 2114 or equivalent will work.

Also, since it seems to be stuck high just piggybacking the new chip on top of the bad one may well work, at least temporarily.

falter
December 9th, 2013, 08:51 PM
Definitely, get the 'scope; I just meant that you don't have to wait for it to repair the PET.

Yes; the -45 or 450ns is the inverse of the speed and anything faster, i.e. with a lower number, should work just fine. I doubt that you'll find anything slower than 450ns, so I'd imagine that pretty well any 2114 or equivalent will work.

Also, since it seems to be stuck high just piggybacking the new chip on top of the bad one may well work, at least temporarily.

I'm curious.. does video ram only corrupt the display when it goes bad, or does it corrupt input/output also? I was noticing that what i assume is a corrupted version of the READY message shows up no matter what i type in.. even nonsense that i wluld assume should generate something approximating a SYNTAX ERROR message.

jac_goudsmit
December 10th, 2013, 05:12 AM
I'm curious.. does video ram only corrupt the display when it goes bad, or does it corrupt input/output also? I was noticing that what i assume is a corrupted version of the READY message shows up no matter what i type in.. even nonsense that i wluld assume should generate something approximating a SYNTAX ERROR message.

I think the way it works on Commodore computers is that when you hit return on the keyboard, the editor copies the logical line from the screen (which may be more than one screen line) to let the Basic interpreter translate it and (if it doesn't start with a number) execute it. In other words: it translates what you see, not what you type. So if the video memory is bad and doesn't store what you type, the Basic interpreter can't interpret it and gives syntax errors.

===Jac

falter
December 10th, 2013, 10:49 AM
I think the way it works on Commodore computers is that when you hit return on the keyboard, the editor copies the logical line from the screen (which may be more than one screen line) to let the Basic interpreter translate it and (if it doesn't start with a number) execute it. In other words: it translates what you see, not what you type. So if the video memory is bad and doesn't store what you type, the Basic interpreter can't interpret it and gives syntax errors.

===Jac

Yeah -- so that kind of makes me wonder if I've got something else wrong.. because typing in complete nonsense doesn't produce any change in prompt. Ie. it just keeps reproducing what I assume is the READY prompt.. no additional lines indicating that it's throwing back a Syntax error.

MikeS
December 10th, 2013, 11:57 AM
Yeah -- so that kind of makes me wonder if I've got something else wrong.. because typing in complete nonsense doesn't produce any change in prompt. Ie. it just keeps reproducing what I assume is the READY prompt.. no additional lines indicating that it's throwing back a Syntax error.Boy, you're really determined to find more problems... ;-)

You're effectively typing graphic characters which are ignored unless they're part of an abbreviated command; ground pin 12 again and you should get the corrupted equivalent of SYNTAX ERROR.

falter
December 25th, 2013, 03:27 PM
Well, the pile o'chips I bought has just enabled my first victory:

16501

And that was off my first try of 5 2114 chips that were in the lot. For now I've just slightly bent the pins out and locked it on top of the existing chip at UF7. Is there any harm to running it like that? Don't really want to get into soldering if I don't have to -- it's pretty snug there.

This operation gives me hope that these chips are good pulls from otherwise dead/retired machines. I'm now going to do a hunt for the RRIOT chip I need to fix my 8050. Cross fingers.

Thanks again for all the help. 1 project down, 8 more to go. :)

falter
December 25th, 2013, 03:29 PM
Another question if I may -- I'm hoping to restore the case to get rid of the ugly rust blemishes -- have any of you repainted, and if so, what paint/color did you use?

Lurch666
December 26th, 2013, 01:12 AM
I think you should reconsider about soldering.At first it looks daunting but it's a simple skill and is quite essential when repairing these old computers.You need an old junk circuit board to practice with and watch a few YouTube videos about basic soldering.
Practice bat first just tinning and joining wires together then desoldering and resoldering a big component like a capacitor or resistor then using a desoldering pump or wick to remove chips.
As long as your practice circuit board is junk it doesn't matter how much of a mess you make of it but try to get an old one as modern circuit boards have surface mount and lots of components squeezed into a small space that's not good for practice.

Once you learn how to solder you will be so glad you took the time.

crock
December 27th, 2013, 12:03 AM
The metal cases can be spray painted with very good results. I think I started a couple of threads a couple of years ago on that very subject.

My approach was to a) remove all loose rust with sandpaper, b) clean the case thoroughly to remove dust c) prime it with Plastikote metal primer (white for the top, black for the base) followed by 2 or 3 layers of a matt top coat.

With regards to colour, I tried several. Brilliant white looks good but doesn't look authentic. If you're looking for the bast match to the original, I found an 'Antique White' was the closest. You could also try metallic purple - that also looks quite good. :-)