chip Rom Mac Classic

[vanhoteen]

Hello everyone!
I am a user from Barcelona, Spain and I suspect that my board has a damaged ROM. I have been experimenting with a Mac Classic and I have noticed that I am getting lines on the screen, just like another user who solved the issue by changing the ROM. Unfortunately, Mac Classics are not readily available in this area, so it is difficult for me to find a functional ROM to replace the damaged one.
I wonder if any of you could help me find a functional ROM or provide me with any other suggestions that could help me solve my problem. I would like to have more options if possible.
I appreciate any help you can provide. Thank you very much in advance.

 

[dochilli]

Did you recap the logic board?
Did you measure the voltages at the floppy port (5 & 12 volt)?
Did you recap the analog board?
Most often a recap solves problems with the classic.
If the ROM is defect you can buy a battery bombed board and use that ROM. Or you can burn a new one:

Fixing an Apple Macintosh Classic with an EPROM Programmer

Does your vintage Macintosh have a bad ROM? Well an EPROM programmer could potentially help save your beloved classic Apple Macintosh.

playeur.com

 

[vanhoteen]

Did you recap the logic board?

I put new ceramic capacitors. Did you measure the voltages at the floppy port (5 and 12 volts)?
At first I think of booting from rom but are those voltages necessary to boot only from rom?
Did you recap the analog board?
No, but it shows voltages and frames when I remove ram. Also, this monitor works with another board that they lent me.


I bought another classic Mac for €60, it arrives on Tuesday, I hope I'm lucky, I have 3 motherboards and 1 monitor, now I'll have a completely new one, but I've printed a classic Mac pcb to make new ones with the remains.



Thank you for the advice and comments, I will check the voltages of both boards with the same symptom and try to revive the new Mac I bought. They say they haven't tested it, but I suspect it has an exploded battery. We'll see what damage it has caused and if I can recover its ROM.

 

[dochilli]

When the classic boots with another LB then your problem is the LB and not the AB. Did you wash the board, when you recapped it? The fluid of the caps must be removed. You can use a toothbrush and water with a little bit of soap. Then rinse the board with IPA and let it dry. I use an oven at 50-60 degrees celsius for 30-45 minutes.
I would recap the AB too. The caps leak. If the AB has no stable voltages the classic will not start and it often shows a checkerboard.
Are you sure that the ROM is in the right position? IIRC there are free pins on one side. When you get another board you can change the ROM and see if the classic boots.

 

[vanhoteen]

Thank you, I checked the voltages and got another classic Mac, which has a surprise processor expansion. But I'll change the capacitors on the AB board. In the latter, accidentally measuring voltages, I shorted pins 12 and 5 of the floppy connector and now it only gives me RAM squares, but before I got a sad face of RAM, I think I damaged some component. But I'm soldering on the new board with patience from other boards that also give me RAM squares. I have 3 boards with the same symptom. I hope to be able to fix two, I also have 1 that is in bad shape, from the microprocessor to the battery everything is rusted but the rest is fine. I hope to be able to fix it.