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well, it seems that this will be the last update for this thread. I bought another cny17-3 and this time, instead of soldering it directly I soldered a socket first. It seems I was killing the octocouplers with the heat from the soldering iron. I have been testing the machines for close to 2...

Thanks for the replies! I did not solder a socket, now that you mention it, i should have. there shouldn't be any thermal expansion in the joints, to get it to work I only need to heat it to about 70 degrees (celsius). but maybe the octos are failing in a way that makes them thermally...

Well, It seems the problem has not ended yet. I replaced the octocoupler with a 4n37. And the computers worked great for a while, I could switch them on and off all the times that I wanted to and all that. then, the next day I went to turn one of them on and the same symptoms returned, wobbly...

Well, I have found the culprit of my suffering (spoiler alert: its my fault) To make it quick, it is the octocoupler.  I thought the one i bought was compatible, but it seems it wasn't. I got started with another one of the other macs to get a break from this one. recapped it, put a new tda...

Hi!, first of all thanks for your reply! I think we are having different problems here, because your board boots first time but after a couple of minutes the voltages drop off. my board does exactly the opposite thing, the thing starts with the checkerboard pattern but after a couple of...

Ok. so I downloaded the bomarc schematics for my board (the late model, without the zener diode dp1) and obviously the first thing that struck me was that at the end of rp1 (22k 3w) there should be 12v ac. I measured and im getting 120v ac both at the start and the end of the resistor AND now...

Hey Elfen, thanks for your reply! I already have reflowed the usual suspects such as the yoke connector and high voltage parts of the board with flux core solder. I also went arround every solder joint with a magnifying glass for visual inspection of hairline cracks. The logic boards do need...

Hmm, the rifa caps apear to be perfect although I haven't tested them yet. As I said in the first post i already replaced the optoisolator, the mosfet, and both 1n4148 diodes. today I will be replacing the TDA ic and see if that solves the problem, I think it will, If not, I will get to...

UPDATE: searching this forum a bit more, i saw a post about blasting heat to the A/B to make it start quicker so i grabbed my smd resoldering station and with the mac turned on started blasting ic's with 150º air, sure enough, the mac started almost instantly this time. I narrowed it down to...

the user im talking about is benanderson89, not 6502 haha. this is his forum post. 

hey, this is my first post to the forum. A couple of days ago I bought a lot of old computers in which came 4 Macintosh classics, not a single one turned on. I chose to start working in one of the 220v models as it is the voltage that my country has. After researching a bit on reddit, this...