9" CRT vc 12" CRT

[crock]

Rob,

thanks to you and to Dave, I solved!

You are very welcome.

There was a broken trace between C5 pin 15 (VIA) and C7 (PIA) pin 18

That was of course option 4 in my list which I forgot to list.

This time it is time for the champagne, but alas, only beer in the smilies fridge:

As my parents arrived in Switzerland this afternoon for a week my booze cache was well stocked. I had beer, red, pink and white wine, prosecco, and laphroaig to choose from.

Who would have thought that there would be this crucial difference between the two ROMs...

Yeah, that is really fascinating. A closer inspection of all the differences between the business and graphics rom is definitely warranted.

 

[giobbi]

Oh sorry, I wanted to say "The Valiant one", but did not know how to say in Italian... Valiante?

Follow Mike's advice. He knows his way around memory circuits.

Valente, valoroso But don't worry, I know what you mean

I'm going to have a dinner (7:30 PM here) but I will check it later. BUT:::: while I was looking at RAMs, don't know why, I'm stucked *again* in a black screen. Yes, again!!!
I don't know if I did something or simply some faulty IC died, again....

This is what the petester is telling me:



What does it mean? what should it be read?

Mike: you told me "I think it would be J3 instead of J7 or J8": can you kindly explain me why? In other words, what is the rule I should follow when I got a wrong data from the basic routine for RAM check? I wish to learn something instead of take the damn'd multimeter and test 200 pins every time :D

-----------------------------EDIT-------------------------------------
J3 is connected to J11 by the RD6 line, firmly.

I've tested again with Nicholas Welte's RAM/ROM adapter and I can affirm (if needed) that the problem is about the RAM bank (obviously)... So I'm assuming the problem is probably related with some component in the page #5 from schematics. But I tested *again* both 7425 and 7410, so I don't know...

--- MAYBE A LITTLE CLUE:
I can remove all RAM chips J2....J9 and I9 without substantial changes in the above picture.
But if I remove just one IC from I2 to I8, then I get a page full of "b". I checked all ram sockets and they seems ok, also the lines between ram chips seems ok, (but who really knows? ;-))

 

[dave_m]

I'm going to have a dinner (7:30 PM here) but I will check it later. BUT:::: while I was looking at RAMs, don't know why, I'm stucked *again* in a black screen. Yes, again!!!
I don't know if I did something or simply some faulty IC died, again....

It means something failed that made zero page (0000-00FF) memory bad. PET will not boot if this important part of memory fails. We'll find the culprit.

 

[giobbi]

It means something failed that made zero page (0000-00FF) memory bad. PET will not boot if this important part of memory fails. We'll find the culprit.

ok... where I could start from?


---------------------------EDIT---------------------------
Ok, ok, almost 24 hours without to post a way to fix... are you trying to make me understand you have a real life out of this forum?? ;-)
Well, I haven't, at least until I will fix this C.R.A.P. (Commodore Really Anticooperative Pc...), this thing is like a splinter in my mind, it's driving me crazy, I don't know what to do more...

*** HELP ME, I wish have a real life too! :D

 

[MikeS]

Still here, just running out of ideas; again, what is the price of gasoline down there? Hope you have some "medication" for those nerves ;-)

Sounds like your question is no longer relevant with this latest development, but FYI:
The 64 instead of 0 suggests that bit 6 in the upper 32k is stuck high; looking at the labels of the data lines on I10 and I11 on page 5 we see that RD6 (RAM Data bit 6?) connects to I3 and J3 and /CAS1 (Upper 32k) connects to the J row of chips.

I think Dave knows more about what each letter of the PETtester represents; hopefully he has an idea or two. It does look like an addressing problem this time though...

Is it repeatable? I assume you've hooked up a reset button; does the PETtester always show the same screen?

Interesting that removing I9 doesn't change anything, but that may just be the pattern that PETtester uses to test.

Did you try replacing I10 and I11?

Try to spend at least part of the weekend in the 'real' world; after 12 years what's a few more days...

 

[giobbi]

Still here, just running out of ideas; again, what is the price of gasoline down there? Hope you have some "medication" for those nerves ;-)

ah ah ah I want to see it alive before to burn it, it must to suffer ;-)

Sounds like your question is no longer relevant with this latest development, but FYI:
The 64 instead of 0 suggests that bit 6 in the upper 32k is stuck high; looking at the labels of the data lines on I10 and I11 on page 5 we see that RD6 (RAM Data bit 6?) connects to I3 and J3 and /CAS1 (Upper 32k) connects to the J row of chips.

thank you, it's clear now.

I think Dave knows more about what each letter of the PETtester represents; hopefully he has an idea or two. It does look like an addressing problem this time though...

What I know is that if I use the Nicholas Welte's ROM/RAM expansion to replace *just* RAM, it works. So it must be something inside the borderline of the RAM management.
Whatever it means...

Is it repeatable? I assume you've hooked up a reset button; does the PETtester always show the same screen?

Yes, it's always the same, no changes. And yes, I have a reset button.

Interesting that removing I9 doesn't change anything, but that may just be the pattern that PETtester uses to test.

A BIG QUESTION: would be possible for you and/or Dave to emprove the petester (petester_2?), in order to display more/better informations about the RAM bank? I.e. checking every RAM chip and displaying what chip is faulty?
I'm not even sure it's technically possible, so maybe my question is a silly question, but it would be awesome if you can! (ok, how many minutes do you need? I'm waiting... ;-) )

Did you try replacing I10 and I11?

Yes, I tried. And not only them But if you have some clue about the most probable culprit(s), I will focus on it and do an extensive search, as I did with the graphic/business edit ROM issue (without a clue I couldn't find that broken trace under a socket!)

Try to spend at least part of the weekend in the 'real' world; after 12 years what's a few more days...

I was far from it for about 2 hours to watch at the football match Italy/Spain, and the Italy lost the match (I'm italian)... ...I strongly feel I have to fix it or the world will end :D

Please, list here the name of the suspected ICs on the board, and I will check them. At least, something to do...

have a great weekend, but don't go away from here ;-)

 

[giobbi]

...sincerely, I don't know what to say...

I checked everything without to find anything. Then, it started to work apparently alone. I don't know what I did; I was simply checking connections, sockets, etc.
I'm merely suspecting that *maybe* I cleaned some dirty part that was causing some short (I use to clean boards with an old toothbrush when I'm checking something, if needed), or I moved some chip. It's quite a shot in the dark, to be honest I don't know what happened. Boh.

However it worked fine for some hours, loading, saving and playing programs and games.

So, I'm sick and tired and I put it again in its showcase, before it change its mind and get stuck again... :D


The 3032 In the lower left corner

Thank you all, again!

-- Giovi

 

[dave_m]

I checked everything without to find anything. Then, it started to work apparently alone. I don't know what I did; I was simply checking connections, sockets, etc.

Giovi,
If it fails again, you may have to look at all circuit traces of sheet 5 of schematic with a magnifying glass looking for a cracked trace on both sides of board having to do with data bit 6 of RAM. Thankfully with the Nickolas board, you can bypass your RAM if needed. Most people would have just left the Nickolas board enabled and let it go at that, but not you, as you were determined to get the original board working. We are all proud of you.

If you are going to work on more Commodore computers, you may have to invest in a used oscilloscope. Keep on the outlook for a old Tektronix 453 or 454. They are small and built solid like a Ferrari. Be patient and you should find one for about $100 USD. Or make friends with a old TV repair guy.

 

[giobbi]

Giovi,
If it fails again, you may have to look at all circuit traces of sheet 5 of schematic with a magnifying glass looking for a cracked trace on both sides of board having to do with data bit 6 of RAM.

Thank you, good to know, I will keep in mind if something will happen in future...

Thankfully with the Nickolas board, you can bypass your RAM if needed. Most people would have just left the Nickolas board enabled and let it go at that, but not you, as you were determined to get the original board working. We are all proud of you.

Thank you

If you are going to work on more Commodore computers, you may have to invest in a used oscilloscope. Keep on the outlook for a old Tektronix 453 or 454. They are small and built solid like a Ferrari. Be patient and you should find one for about $100 USD. Or make friends with a old TV repair guy.

I will try to find a used one; maybe in Italy will be easier to find, lower prices than Brazil. Thank you for the suggestion!

cheers,

Giovi

 

[giobbi]

Just few words to say I put a page with my two cents about fixing a garbage screen:

http://www.verrua.org/pet_repair/index.html

or go to www verrua org and choose "how to fix a CBM 3032" from the home page.

Definitely, this isn't the "ultimate guide" or "what you should absolutely do"; it's quite like "if you don't know what to do, and you're newbie and dummy and poor, and you don't own neither scope nor knowledge, and if you're left alone with yourself you usually tend to do silly things, then maybe you could take a look to this page and maybe you will find some useful info, and maybe if you're very lucky you will fix it; or at least ask to Mike and Dave on vintage-computer.com forum" ;-)

Please report me any mistake (grammar, typo and concept) and I will fix them.
Ah, since I'm lazy, I've done this guide with ms-word and saved as html, so it will took a while to load pictures.