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Macintosh classic with horizontal stripes no chime already recapped
Posted by: AppleWoz on 2024-01-31 11:36:11
Hi all guys, this time with this classic Macintosh even after recap and track reconstruction it didn't go well for me, I'm having a problem with horizontal stripes, I don't hear any sound, obviously the analog board is working because I have another motherboard to try, this is the first time I've seen horizontal stripes, generally what caused it? I assume the ua2 RTC chip is dead, is it possible to replace it somehow?
Posted by: Kouzui on 2024-02-02 21:51:53
Interesting. I got that effect when I shorted the pins on the side of the board to test my battery-bombed classic. It wasn't the expected behavior, and I got the computer working only when I used a repro logic board.
If i had to guess the reason for your computer doing it, I'd say either one (or more) of the traces is still broken or there's a short somewhere it shouldn't be.

Edit: Could you show some closer pics of the RTC chip, or tell us about what condition it's in? You can't really find replacements for it, but it may be *an* issue if you think it's dead for some reason.
Posted by: AppleWoz on 2024-02-03 00:27:18
Interesting. I got that effect when I shorted the pins on the side of the board to test my battery-bombed classic. It wasn't the expected behavior, and I got the computer working only when I used a repro logic board.
If i had to guess the reason for your computer doing it, I'd say either one (or more) of the traces is still broken or there's a short somewhere it shouldn't be.

Edit: Could you show some closer pics of the RTC chip, or tell us about what condition it's in? You can't really find replacements for it, but it may be *an* issue if you think it's dead for some reason.
I checked all the traces one by one comparing them with the good motherboard I have and they are ok, I think the RTC chip is shorted, is it possible to replicate it? I saw someone who did it for Macintosh SE30
later I'll add some better photos of the RTC, basically on one side it didn't have pins exposed, they were eaten by the acid so I had to use a dremel to scrape the plastic and solder on top
Posted by: Kouzui on 2024-02-03 05:57:31
is it possible to replicate it?
I think someone was working on a way to replace it, but I don't remember what the project was called. It's probably somewhere on here, though.

Why do you feel it's shorted?
Posted by: AppleWoz on 2024-02-03 15:48:22
I think someone was working on a way to replace it, but I don't remember what the project was called. It's probably somewhere on here, though.

Why do you feel it's shorted?
I assume it is damaged because the Macintosh does not start and all the tracks seem to be restored and it is also completely delivered, I don't know if this information can help but I saw that by inserting the RAM expansion card this screen disappears and the checkered screen appears
Posted by: marcelv on 2024-02-04 15:26:56
You can remove the RTC chip, the classic will start without the chip present (if no other problems exist on the board)
Posted by: AppleWoz on 2024-02-05 00:55:53
You can remove the RTC chip, the classic will start without the chip present (if no other problems exist on the board)
Really? I didn't know that the classic booted even without RTC, I'll try to remove it seeing what condition it is in, thanks
Posted by: marcelv on 2024-02-05 01:02:51
I have a classic with even more damage from the leaking battery. Removed RTC and sound chip, D1, D2, Y1, C1, C2 to clean beneath and repair a lot of tracks. Tested the board before replacing these components.
Posted by: AppleWoz on 2024-02-05 05:37:44
I have a classic with even more damage from the leaking battery. Removed RTC and sound chip, D1, D2, Y1, C1, C2 to clean beneath and repair a lot of tracks. Tested the board before replacing these components.
I also removed the chips from the PCB because some contacts were missing underneath too obviously, I'll double check everything again at this point
Posted by: AppleWoz on 2024-02-05 05:46:58
the initial state of the card was really bad, the acid got everywhere, there are so many connections to check, but if you tell me that it can boot even without the audio chip and RTC, I'll focus on everything else by removing the chips again
Posted by: AppleWoz on 2024-02-11 05:31:02
I rechecked all the connections above and below the PCB, I found 2 connections missing but they didn't change the result, I tested the ROM on another board and it works without problems, I compared the board with a perfectly working one using a thermal imager and the same chips heat up in a completely identical way, I really can't understand, can the RAM cause problems of failure to start with horizontal stripes? It's strange to me that if I add the additional RAM module it changes the checkered screen instead of horizontal lines and I see, like, some artifacts on one side
Posted by: Kouzui on 2024-02-11 11:20:36
I rechecked all the connections above and below the PCB, I found 2 connections missing but they didn't change the result, I tested the ROM on another board and it works without problems, I compared the board with a perfectly working one using a thermal imager and the same chips heat up in a completely identical way, I really can't understand, can the RAM cause problems of failure to start with horizontal stripes? It's strange to me that if I add the additional RAM module it changes the checkered screen instead of horizontal lines and I see, like, some artifacts on one side
From my experience with RAM, if something's not connected right it would show a sad mac as opposed to doing what yours is doing.
Posted by: Arbee on 2024-02-11 12:09:06
From my experience with RAM, if something's not connected right it would show a sad mac as opposed to doing what yours is doing.
On a Classic? The RAM is also the video frame buffer (and the sound buffer) so I'd be surprised if it could show a Sad Mac or play a chime if there was a RAM problem. On later machines the startup diagnostics deliberately don't rely on RAM and the audio and video have separate RAM and VRAM so they can self-diagnose a lot better.
Posted by: Kouzui on 2024-02-11 13:05:18
On a Classic?
Yup, if you check my post history you can find my thread on a restoration I did.

Edit:

Bombed Macintosh Classic Failing to start after attempted fix + recap

I'm working on a Macintosh Classic which has unfortunately seen the bad side of a clock battery. The damage didn't seem to be too terrible to me, but I replaced all the caps on the logic board (have not touched the analog board, and don't intend to if I don't have to). I've also repaired a few...
68kmla.org 68kmla.org
Posted by: AppleWoz on 2024-02-14 08:30:24
From my experience with RAM, if something's not connected right it would show a sad mac as opposed to doing what yours is doing.
I compared all the connections between CPU ROM and BBU, everything is identical to the working motherboard, I tried to desolder the UK8 ram and in fact it gives me a ram error on the screen, if I look carefully however I see some small artefacts (dots arranged in vertical way), can you suggest anything for the diagnosis? I am going crazy
Posted by: Kouzui on 2024-02-14 15:39:45
Interesting. It seems like you're really close. Unfortunately, I don't really know why your machine is behaving the way it is. The only thing I can think of is that when I got a similar screen to the lined one, it was because I was shorting two of the debugging pins on the side of the board (as you can see in the thread). It's not much, but maybe that's the right direction to look.

Also, does everything look good on the underside of the board?
Posted by: AppleWoz on 2024-02-15 01:21:15
Interesting. It seems like you're really close. Unfortunately, I don't really know why your machine is behaving the way it is. The only thing I can think of is that when I got a similar screen to the lined one, it was because I was shorting two of the debugging pins on the side of the board (as you can see in the thread). It's not much, but maybe that's the right direction to look.

Also, does everything look good on the underside of the board?
I have to check those two points if they are shorted, maybe the via chip ub5 is shorted
Posted by: AppleWoz on 2024-02-15 14:29:22
that area is not shorted, everything is normal, there is something that does not allow the rom to ram loading phase
Posted by: AppleWoz on 2024-02-23 03:53:24
Is there anyone who can explain to me why if I press the reset button nvram doesn't work? does it only work if the rom is loaded? the reset button works because if I press it I hear the speaker click, I really can't understand where the problem is and above all where I should look at this point I've run out of ideas, does anyone have any suggestions? Thank you

I also swapped the UE3 UF3 UI6 and UH6 chips from a working card without any changes
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