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g'day

Here I am, a bit late (I got sick) but I bring news. I have reflowed every cold/cracked joint on the board and every connector joint, and double checked afterwards... to be honest, there weren't many but I still resoldered the connectors for good measure. Readings without the floppy attached...

Thanks for the tip... I'll do that tomorrow and update the thread after I reflow every bad joint (it's 1:30 am and I'm very tired)

I just checked the continuity, and both of the switches work as intended, nothing when the switch is not pressed. Well last time this thing worked the RAM wasn't a problem... I also tried reseating it and cleaning the connectors both on MB and RAM, and nothing changed. Haven't reflowed it... I...

I already tried lowering the voltage and it did not change anything. I also reseated the rom, the ram, tried putting in a battery, but I got no luck whatsoever.

Welp, the other day I got a new analog board. Recapped the three RIFAs, the seller said it was taken from a working mac, and guess what? It still has the same issue! I really have no idea.... could it be a CRT issue? Maybe the CRT has weird current draws or has issues, I don't know. Really stuck!

I checked online and found at This github page that Q12 can be a "BR103 reversed" (?) Now I don't know if that's possible or how to reverse a transistor, so, not really sure...

Searching online I read that Q12 doesn't have a direct replacement as it has been discontinued, and, can't find anything else... what can I do? Also It's almost like Q10 is glued to the metal bracket, how would I remove it?

Well, I was checking voltages between C35 and C39, I am getting around 300/301DC.... while I was doing that I heard a bang, and, it was Q12 that said goodbye (it exploded, popping the fuse too). And also seemed to burn R53 too....

Unfortunately, I have already tested every cable… the analog board is not even getting 12v or 5v to the power rail, and no high voltage as well…

Right- I am getting around 230V after the thermistor with switch on.... what else could I test

Well, I’ve replaced what is essentially everything on the AC part… And, it doesnt work. Same issue, no power to mainboard, no noises whatsoever, just complete death.

Thank you for the schematics. Really needed those!! I did indeed spend some time testing everything in the AC section. CR31 is indeed faulty, and also is CR30... with all these faulty components I'm starting to be amazed this thing even turned on a couple of times! I will also change the...

Thank you for all the advice. By fixing the AC section which parts do you suggest me to concentrate more?

I checked the bridge, and it seems that CR25 reads 0,001V in both directions... certainly have to change that. Good to know this, because the two smaller 4700 pico farad ones seemed really cracked up. I will also change the 0,47uF one just in case. I have re-checked it, and now it reads around...

Hello everyone. I recently bought a Macintosh Plus 1MB with an analog board problem. The computer initially had a strange issue where it would boot-chime loop for some minutes (sometimes multiple restarts per second), then when it warmed up it worked normally. Initially I simply thought it was...