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Stèphane's and Alex' PET ROM checks

:D Hi! I'm Alex, Carlsson have many patience with me ;) to help to revive my 3032.
I'm reading new post about possibility of power source problem: how can i test if two big capacitors (one near power & one on mainboard) is faulty?
Thanks!

p.s. sorry for my english :blush:
 
I've made some test...


img0071small.jpg



img0070smally.jpg


...is that voltage correct?

How can i test capacitors?

Thanks!
 
Alex,
The 9.75 Volts may be OK as it looks like the unregulated +9V, and if the capacitor on the board is C62 (4700 uF), the schematic indicates it is input to the +12V regulator so +20.9V is probably OK also. So no need to test capacitors.

Check the +5V at various chips on the board like the CPU and ROMs and 6522. Also check for +12V on pin 8 of the RAM and -5V on pin 1 of the RAM.
 
As a side note, Alex told me he has invested in a True-USB GQ-4X EPROM programmer, eraser and a bunch of 2532 chips so he will be able to double check the ROMs and EPROMs locally to see if they are toast or not.
 
...the battle "man against machine" continuous ;)

In next days i'll check IC voltage and in 2 weeks programmer it will arrive :D

Then i hope to find why PET 3032 work few minutes and than stop.
 
Why not try cooling some of the chips in the meantime? Hook up a push button or some pieces of wire to ground the reset line so you can repeatedly reset without the strain of a power cycle, and cool the various chips with a cooling spray or just an ice cube in a plastic bag.
 
Hi MikeS!
My PET works few minutes after i put new reprogrammed eproms and then stop and don't startup ok again :(
I've check ICs temperatures after 1 hour but all seem normal.
In next week i try to reprogram eprom and then i'll try again.
 
alex1690 said:
Hi MikeS!
My PET works few minutes after i put new reprogrammed eproms and then stop and don't startup ok again :(
I've check ICs temperatures after 1 hour but all seem normal.
In next week i try to reprogram eprom and then i'll try again.
Click to expand...
Have I got this right? You put in freshly programmed EPROMs and it works for a short while, then it dies and won't run again until you put in another set of freshly programmed EPROMs?

Sure sounds like there's a problem with at least one of the EPROMs, your programmer, or the way you're erasing them (if you are)...

I don't know what EPROMs they are, but they do come in different versions requiring different programming voltages; I've never tried it but maybe programming a 25V part with 12.5V might cause this sort of thing.

Still might be worth while cooling them and resetting; might help you find the bad one if one is indeed bad.
 
The motherboard when I sold it to him was equipped as following:

$C000 901465-01 ROM (Basic V2)
$D000 901465-02 ROM (Basic V2)
$E000 901447-24 EPROM 2716 (Editor V2 graphics keyboard, no CRTC)
$F000 901465-03 EPROM 2532 (Kernel V2)

This motherboard ran fine before I sent it.

It arrived in Italy on November 2, and worked for four days. On the 6th, he suddenly got the monitor prompt when booting the computer.

When he sent me all his chips, I found the 2532 Kernel chip had gone bad. The 2716 Editor chip and the original ROMs however were fine.
I programmed a new 2532 and also completed his set of Basic V4 chips so those should work.

He received the chips in early January and found the V4 chipset still only produced garbage. The V2 chipset however worked for a day, he even saved and loaded some programs to floppy drive. Then on January 16, the PET produced garbage characters even with this chipset. Since last time it crashed into the monitor but now it produces garbage, it is hard to say which chip has gone bad this time.

Of course the motherboard itself could be faulty, but should a malfunctioning board be able to work for a day or two when one inserts new ROM chips? The big chips: 6502, 6522 and two 6520 have pretty much been the same all the time and since it has worked a couple of times, I wouldn't suspect a problem there?
 
You are right... very strange problem.
I think may be power supply but voltage seem ok.
But "i love my Pet" ;) and with programmer and all your help i hope we'll find a solution :D
 
Better check so you didn't leave anything below the motherboard when you fastended it into the case, something that might cause shorts.
 
Hi,

Back from hollidays, I gave a new chance to my PET to start using the ships Carlsson kindly sent me.
I do not know what i did wrong at frist try 3 weeks ago, but now it is working like a charm !!!

I finally got the BASIC welcome screen !!! The floppy drive also works perfectly fine.
I am having great fun booting and using the PET which seems to be totally reliable now.

Thank you again to all who contributed to this resurrection :) !
I would have never been able to fix my PET without your great assistance.

Stéphane.
 
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