Craig Sawyers [mailto:c.sawyers@...],
answering Jose Gavila:
<snip>
I'm looking at the schematic of the 545A, and I suspect that
the 545B has
the same 350V supply. The (silicon) bridge rectifier feeds the 125uF
reservoir capacitor through two ten-ohm 1W resistors in
parallel. It also
has an 82k resistor in parallel.
So check that the 10-ohm resistors are present and measure
correctly, and
the same with the 82k.
I don't think that trouble in those resistors could
account for a ripple. IIRC the purpose of the 82K
is to prevent some cap (maybe this one) from getting
reverse voltage during warmup. The 10's are there
mostly for troubleshooting. You measure across them
to calculate current.
Even if you don't have a manual or a cap tester, you can
find out if the cap is ok. Measure the current
as I mentioned above. The formula for current
in a cap is I = C * dV/dT . Estimate
dV/dT from your scope trace. Plug in I and
dV/dT. Does C come out near the printed value?
To get in deeper, you really need a manual.
It tells what I should read, and it might even
say how much ripple is acceptable. In any case,
how's the +350 line? If it's smooth over the
specified range of line voltage, you're ok.
Regards,
Dave Wise
