Comments below:
JOSE V. GAVILA (EB5AGV/EC5AAU) wrote:
So, armed with the manual, I have been looking again at the power supply...
to find that, yes, there is a trouble. -150V is good, as is +100V and +225V
(less than about 5mVpp ripple on them). BUT +350V and +500V show no less
than about 20Vpp ripple!. As the +500V is based on the +350V supply,
culprit should be on that last supply.
Yes, I think you are on the right track.
But I have not yet been able to
locate the ofending part. Obvious things, as the +350V electrolytic cap
filter and the 6080 rectifier are fine.
There are TWO electrolytics to check here: C679C and CC730. Did you check
them both?
Also, the 6AU6 comparator is good
(I have checked in both cases with good tubes). Although they check fine
on-circuit, I suspect one of the solid state rectifier diodes just after
the transformer winding could be bad so the power supply has not enough
available current and voltage drops on the 'bad' semicycle... But I need to
check this. Anyway, is there any idea from your side?
It could be a bad diode. If it were shorted it would blow fuses so if it is
bad it must be open. If it were open, the ripple you see on the power supply
would be at line frequency (probably 50 Hz in Spain) rather than two times line
frequency like a nornal bridge rectifier would produce.
About the 1A1 plug-in, it is of the 'old' type (6 nuvistors on it). It
seems to work fine. Hope it keeps going, as the nuvistors are not cheap
items ;-)
Regards,
JOSE
Good luck, Jose,
Stan
w7ni@...
