Denial

I think my PET has lost the will to live ..
I have replaced all electrolytic capacitors except the main one ...that big green beast in the photos..
Left the PET soak testing for an hour or so ..
When I checked again ..the cursor had stopped flashing ..??
so I rebooted ..
but nothing on screen ?
the monitor is still working ..because as I now switch on ..sometimes get a full screen of ASCII characters as the power comes up..
but only briefly.
Possible Rom failure ??

It's just not my day is it ?

Took several attempts ...as I only get a brief chance to snap the screen..
usually after the second boot attempt in quick succession ..
anyone seen this before on a PET ?

@ViperSan
I strongly suspect every time you start up your PET to check it, you cause even more damage or run the chance thereof.

I know of only 2 people who can fix PET computers. These are Ray Carlsen and Jean-Claude Lachapelle.

eslapion wrote:@ViperSan
I strongly suspect every time you start up your PET to check it, you cause even more damage or run the chance thereof.

I know of only 2 people who can fix PET computers. These are Ray Carlsen and Jean-Claude Lachapelle.

Well ...looking at the board it is indeed a very chip populated board ...
I could very easily retrofit chip sockets for evey chip ..thus chip swapping would be easy ..
..but of course I dont have another to borrow chips from.
I'm guessing cpu ..rom...or clock issues..
..all of which would be fixable..
I'll start with the cpu which is a 6502 and I have a spare ..
then the 6522 chips ..which I also have.
The problems come when the roms become taget ...as these might be tricky either to source or clone..
Which is why I was hoping to narrow down the possibilities.
..by asking if any members have seen a similar PET fault..
Norm perhaps ?
rgds
VS

Clutching at straws I just chip swapped the 6502 and the 6522 ..
No change..but at least these are now eliminated.
cest la vie

Past one issue and on to another. That issue could be caused by a bad DRAM chip. They are 4116 chips IIRC. When I had that issue it just took a 4116 chip i had and piggy backed each one after another until there was a change. That sometimes works. Also there are more PET experts on The Vintage Computer Federation website http://vcfed.org/wp/ They have a lot of knowledge on repairing pets.

Edit: This may come in handy: http://blog.tynemouthsoftware.co.uk/201 ... y-16k.html There is a ton of pet repairs on this website (it helped me a lot).

Thanks Norm ..
There are 16 x 4116 chips on my mobo ..half of which are socketed ..so these 8 will be easily swapped ...and I might well socket the other 8 ...
If I still dont get a result then I will check out those links..
There are also 2 x 2114 chips..
Display/screen memory perhaps ?
What would be useful is a full list of the MOS chips and what they do

1 x 801462-22 (UD9)
1x 901447-29 (UD8)
1x 901465- 21 (UD7)
1x 901465-20 (UD6)
1x 901465-23 (UD5)
1x MSM2716AS (UD4) ??????
1x (UD3) Empty socket
1x DM74154N (UD2) ????
1x 90147-10 (UF10) >>>I think this is Character ROM ?




The cpu = 6502
2x 6520 (PIA)
1 x 6522 (VIA)



various logic chips
555 Timer (standard on CBM machines)

All of that info including schematics, firmware etc is here: http://www.zimmers.net/anonftp/pub/cbm/ ... index.html

@ViperSan
AFAIK, 4116 DRAM chips have a very cryptic electrical requirement: they need -5V,+5V and +12V sources to work properly.

Since there seems to have been problems with the internal power supply of your PET 4032, perhaps one of these voltage sources has a problem. A good multimeter should be able to tell you if one of these is cause for concern.

Been in touch with Dave Curran at Tynemouth software ...
I have on order a combined Rom/Ram chip that plugs into the cpu socket ..
and also a diagnostics chip ...
both are his own design ..and should enable me to either diagnose and fix the PET or just ..substitute thereby fixing..
I'll let you know.
rgds
VS

https://www.tindie.com/products/tynemou ... odore-pet/

http://blog.tynemouthsoftware.co.uk/201 ... stics.html

IT'S ALIVE!!!!
A good bit of tech help from Dave Curran ..and His Highly recommended diagnostic chip ..
Non of the RAM banks were working ..
diagnostics shown all chips with errors ..
So what were the chances ? ...I figured it was more likely that one of the supply rails to memory was down ..
..and indeed it was ..
No 12v (VDD) ..
traced to a dead tantalum capacitor ..
replaced with electrolytic ...and back in business..

Nice..Congrats!

Very few of the keys were working ...
took about 2 hours to strip it down and clean everything ..and wipe over the keyboard contacts with iso alcohol..
But the KB is like new now..
Another job done.

This is great news, alive for the next 40 years of work

Glad you got your PET 4032 working.

I had the same problem with the power socket of my VIC-1540 floppy drive. I turned it on, walked away and came back a few minutes later to smoke coming out of the back end. The power socket was burned up. It was the same white coloured part that was in your PET. Since the VIC-1540s were early (ca. 1980-81) then it makes sense that these might have been the same supplier as used for the power socket of the PET4032.

Seems these white components fail spectacularly nowadays.

PS: the VCF guys and Dave at Tynemouth software helped me to get my SuperPET working too, earlier this year. Dave at Tynemouth must get a constant stream of people coming to him with dead PETs.

And it's funny to see how all of our "PET failure" threads have similar endings on VCF and elsewhere, when the computers start working again. All these posts begin with with "IT'S ALIVE!!!!" and have screenshots with thanks to those who helped. This is a good thing, but I find the similarity interesting.

Here's mine:
http://www.vcfed.org/forum/showthread.p ... post445138