On Wed, Jun 27, 2018 at 07:11 pm, musicamex wrote:
This REALLY helps as it is the only detailed repair dealing with almost
exactly my issues.
May I disagree with the end of the sentence? The only common diagnosis so far is that +55 and +110 are slightly low and that +15, +5 and -8 are close to zero.
You measured +22.5 V or so after the +15 rectifier bridge. So probably nothing wrong there, while the video starts with a problem there.
Your slightly low +55 and +110 might both be caused by an improperly set or dirty adjustment R1538. This can't explain the other faults, the other reg voltages would just be slightly too small. +22V will be OK otherwise +55 would be far off.
The dead +15 will always cause a failing +5 and -8 and might simply be the only cause here of these failures -- even likely in my opinion.
Your dead +15 could be due to just one cap (C1559) or diode (CR1559), or an open R1553.
I think you would have made much more progress already if you had done the suggested measurements in earlier posts (you didn't report any.) In the best case you would have been more optimistic than in your last post!
BTW: I had no patience to view the whole video. Bu I saw at 32-33 minutes that the AC input voltages to the bridge rectifiers are measured. For +15 that was 1.3 V. I find this hard to believe. Apparently then there is nearly a shortcut loading the transformer winding. I guess this would immediately blow the main fuse?
Albert
