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 some soldering problem, and in fact there was a couple of cracked joints, that I fixed and it worked for some hours. Then the issue reappeared; except this time it rebooted just a few times, and, total silence and nothing... completely dead. I checked all the capacitors and found some that had some measurements off... including one that had a corroded leg (C18). I carefully replaced them (C18, C27, C28, C24), and, unsurprisingly the computer still wouldn't do any kind of noise or sign of life. So I spent some hours checking every connection and voltage; at first I noticed that the logic board was not getting any voltage, apart from a pin that was very low (0,3V or so)... Left the computer off for some minutes, came back to test again voltages, and when I flipped the switch the fuse and my main power popped... and now I'm here writing this post.
Maybe this is an incredibly stupid thing, but it's my first time operating such an old computer... the oldest thing I've ever put hands on is an iMac G3...
I checked the Dead Mac Scrolls for help, and looking through there I noticed that CR21 has all blackened legs with some corrosion on it, almost like it was burnt. I also checked CR5 and noticed that the Ohms for it were much lower the expected value.... which points at a flyback failure... (still unsure)...
Something else I noticed, was that transformer T3 looked kind of damaged (?), almost like some pins of it were burnt, and the coil on top has some oxidation... I don't know if it's bad, but it is worth mentioning.
Another thing, the seller told me that his father had repaired it back in the day, 20 years or so, I don't know what kind of repairs he did but I did notice a weird junction on Q6... maybe it's normal, maybe not, I don't know.
This is an european Macintosh Plus (model M0001AP), 220V - 240V rated, the fuse was a 1.6A 250V...
Any kind of help is welcome... this has been frying me for the past weeks....
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 some soldering problem, and in fact there was a couple of cracked joints, that I fixed and it worked for some hours. Then the issue reappeared; except this time it rebooted just a few times, and, total silence and nothing... completely dead. I checked all the capacitors and found some that had some measurements off... including one that had a corroded leg (C18). I carefully replaced them (C18, C27, C28, C24), and, unsurprisingly the computer still wouldn't do any kind of noise or sign of life. So I spent some hours checking every connection and voltage; at first I noticed that the logic board was not getting any voltage, apart from a pin that was very low (0,3V or so)... Left the computer off for some minutes, came back to test again voltages, and when I flipped the switch the fuse and my main power popped... and now I'm here writing this post.
Maybe this is an incredibly stupid thing, but it's my first time operating such an old computer... the oldest thing I've ever put hands on is an iMac G3...
I checked the Dead Mac Scrolls for help, and looking through there I noticed that CR21 has all blackened legs with some corrosion on it, almost like it was burnt. I also checked CR5 and noticed that the Ohms for it were much lower the expected value.... which points at a flyback failure... (still unsure)...
Something else I noticed, was that transformer T3 looked kind of damaged (?), almost like some pins of it were burnt, and the coil on top has some oxidation... I don't know if it's bad, but it is worth mentioning.
Another thing, the seller told me that his father had repaired it back in the day, 20 years or so, I don't know what kind of repairs he did but I did notice a weird junction on Q6... maybe it's normal, maybe not, I don't know.
This is an european Macintosh Plus (model M0001AP), 220V - 240V rated, the fuse was a 1.6A 250V...
Any kind of help is welcome... this has been frying me for the past weeks....
