Hi,
What can possibly cause this mess?
Can this happen if the MC7812CK is faulty?
Both fuses are blown and the elcos leaked.
I Hope it‘s not a problem upstream in the amp Box.
I think I‘ll first desolder the cables from the power tranny and measure the secondaries. Although I don‘t think it‘s to blame; what do you think?
Thanks for your help
BR
Olaf
What can possibly cause this mess?
Can this happen if the MC7812CK is faulty?
Both fuses are blown and the elcos leaked.
I Hope it‘s not a problem upstream in the amp Box.
I think I‘ll first desolder the cables from the power tranny and measure the secondaries. Although I don‘t think it‘s to blame; what do you think?
Thanks for your help
BR
Olaf
Attachments
Should read blown power supply.
Seems one can‘t change topic after posting.
Anyway there hadn‘t been a thunderstorm, wonder what happened.
There must have been massive current, those diodes can handle 200 Ampere Short Term of I understand the datasheet correctly.
The 6000mfd elco is bulged, of that info helpes.
Seems one can‘t change topic after posting.
Anyway there hadn‘t been a thunderstorm, wonder what happened.
There must have been massive current, those diodes can handle 200 Ampere Short Term of I understand the datasheet correctly.
The 6000mfd elco is bulged, of that info helpes.
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Test each part individually, and replace the bad ones, starting with the power transformer.
Possibly a shorted electrolytic capacitor caused this cascading failure. Diodes will only tolerate
very brief high current rectification pulses, not the kind of heavy currents that happen in a failure
and blow the fuse.
Possibly a shorted electrolytic capacitor caused this cascading failure. Diodes will only tolerate
very brief high current rectification pulses, not the kind of heavy currents that happen in a failure
and blow the fuse.
Yes, thanks for reply. Hope it‘s not the power transformer. Should become difficult to find a type with similar secondaries.
I also suspected the capacitor, if it developed an internal short, massive currents flow. But I never had a shortend capacitor.
I also suspected the capacitor, if it developed an internal short, massive currents flow. But I never had a shortend capacitor.
This is not unusual for older equipment, especially when operated at high voltages and temperatures.
The ARC circuit boards are very delicate, and are easy to damage when reworking.
The ARC circuit boards are very delicate, and are easy to damage when reworking.
I guess you heard, my SP11 blew the windings for the phono stage filaments. That AR design gives me nightmares.
That would be less common, but is possible. All the parts on the board should be tested.
Looks like first the electrolyte leaked out of the capacitor, and being acidic, it conducts large currents driven by the diode voltages, which then causes over heating, burning and blown fuses. The leak may simply be due to age, or a poor capacitor design, and likely accelerated by heat from the regulator.
Yes, would be nice, if that‘s the cause.
I‘ll inform you, when I will be succesful 😁
Thank you
Ah, Rayma was right, the Cooper traces easily liftet from the board. I had to replace them with copper foil.
Thanks also…
Thanks also…