retroguy2019
Member
Hi everyone! My first post here (I think...)! My name is Marco, a vintage computer enthusiast. I have a collection of old Macs, Amigas, Ataris, MSX and such... simply love them! I spend a lot of time restoring them to bring them back to their glory days... now, I am strugling to bring back a Mac CC...
Yes, yes... sorry about that! But, yet again in this forum, we have an issue with a Mac CC :-(
I have looked all over for info about this, couldn't find it anywhere. I am about to throw the towel here, so I thought about asking for help before doing it
Little background first... I bought this Mac CC a while ago, for a decent price at eBay. The Logic board was totally damaged by battery corrosion, but I was able to salvage it after recaping and cleaning it up. The CC booted up but image was distorted. I then proceeded to recap the analog board. I replaced almost all the caps, along with the DL21 & 22 diodes and RL62 (47 Ohms) and RF11 (390 Ohms) resistors (the ones that normally looks burnt). CF8 cap was part of the recap work, of course (replaced with a 3300uF 25V 105C). After the work, the CC turned on and image was looking fine. It lasted for a few boots and then I started seen varying brightness and flickering, up to a point where the screen went totally dark. CC was still on and working, only the screen went dead.
O opened it up once again only to realize the resistor RL62 was scorched again. I, once again replaced it and also double checked for solder cracks and other issues. Reflew some solder joints that looked sad and give it another shot. Same thing... The CC stays on for a bit, then image gets unstable and, then, blackness. Again, RL62 scorched.
It seems there is a problem somewhere in the high voltage path. I am no electronic engineer... can't do complex troubleshooting here (I don't have an osciloscope and, even if I did, I have no clue how to use one)...
Any ideas what to check? I am ordering a replacement CF8, just in case... but I don't think that's where the problem is. Maybe the diodes?
NOTE: You will notice, on the back of the board (2nd picture), there is a pretty bad burnt cluster where the diodes and the affected resistor connect. Even though it looks bad, the traces and connectivity is fine. I double checked that with a multimeter and it tested fine. I also resolder all those components in place, so the solder is fresh. The burning was already there before I started the restoration. Those analog boards don't look well designed... but it might be an indication of an issue somewhere else... not sure.
Follow some pictures...
Thank you everyone!!
Yes, yes... sorry about that! But, yet again in this forum, we have an issue with a Mac CC :-(
I have looked all over for info about this, couldn't find it anywhere. I am about to throw the towel here, so I thought about asking for help before doing it
Little background first... I bought this Mac CC a while ago, for a decent price at eBay. The Logic board was totally damaged by battery corrosion, but I was able to salvage it after recaping and cleaning it up. The CC booted up but image was distorted. I then proceeded to recap the analog board. I replaced almost all the caps, along with the DL21 & 22 diodes and RL62 (47 Ohms) and RF11 (390 Ohms) resistors (the ones that normally looks burnt). CF8 cap was part of the recap work, of course (replaced with a 3300uF 25V 105C). After the work, the CC turned on and image was looking fine. It lasted for a few boots and then I started seen varying brightness and flickering, up to a point where the screen went totally dark. CC was still on and working, only the screen went dead.
O opened it up once again only to realize the resistor RL62 was scorched again. I, once again replaced it and also double checked for solder cracks and other issues. Reflew some solder joints that looked sad and give it another shot. Same thing... The CC stays on for a bit, then image gets unstable and, then, blackness. Again, RL62 scorched.
It seems there is a problem somewhere in the high voltage path. I am no electronic engineer... can't do complex troubleshooting here (I don't have an osciloscope and, even if I did, I have no clue how to use one)...
Any ideas what to check? I am ordering a replacement CF8, just in case... but I don't think that's where the problem is. Maybe the diodes?
NOTE: You will notice, on the back of the board (2nd picture), there is a pretty bad burnt cluster where the diodes and the affected resistor connect. Even though it looks bad, the traces and connectivity is fine. I double checked that with a multimeter and it tested fine. I also resolder all those components in place, so the solder is fresh. The burning was already there before I started the restoration. Those analog boards don't look well designed... but it might be an indication of an issue somewhere else... not sure.
Follow some pictures...
Thank you everyone!!
Last edited by a moderator: