68kMLA Classic Interface

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Macintosh SE FDHD problem :P
Posted by: MacintoshProblems:P on 2023-04-08 08:43:42 Good morning/good evening. Here I am for the news: I took apart the Sony power supply and double checked the voltages and electrolytics, used a couple of voltmeters to verify that the voltages were present at the same time as the power up and everything was running consistently. I also checked the -5V obtained on the analog board from the -12v coming from the power supply, and that works fine too. Finally I looked for the peaks with the oscilloscope but all the voltages seemed "clean" to me. This is what I managed to do in this period, in the meantime I ordered the ceramic capacitors from lopgica (104z and 103z) which I will mount as soon as they arrive. For now, Happy Easter everyone from me and the SE with its Easter Egg!
Posted by: MacintoshProblems:P on 2023-04-11 02:33:29 Update: Good news, it's Fixed! So let's see what happened: while waiting for the small 100 nf capacitors, however indispensable because I found others with rusty legs, it occurred to me that I had seen some small black spots on the Rom's feet, I decided to clean them with a sheet of 800-grit sandpaper. The little SE started working again! Rows disappeared on startup. Perhaps I should have focused more on ROMs and the flaws connected to them. Also the other integrated ones had stains on the feet, 30 years and more are not a few for a correct conservation. Perhaps some dirt was also found in the socket of the integrated circuit. Also, the machine must have been stored in a humid environment which severely damaged some parts. A final example was the failure of the internal clock: the capacitor C18 connected to the quartz Y1 had a broken leg from the oxide. At the moment I have replaced it with a 33pF 10% disk ( J ) but with 6Kv of isolation. I had nothing else. The clock works, but the capacitor will need to be replaced with something more accurate and 50V. In the end I hope that my experience can be useful to those who find themselves in a similar situation. Happy continuation everyone!
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