I just got off the phone with the guy at Ten Tec who works on the
Titan 425's.
I asked him about replacing all the caps if one is bad, which
someone here or on another list had said was necessary. He said no,
that is NOT necessary. Simply watch the plate voltage, and if you
see it dropping, or if you get reports of hum, look for another bad
cap and replace it.
BTW -- it's pretty easy to check these caps with an old-fashioned
ohmmeter. Hang the meter across each one for a few seconds to charge
it, then reverse the meter. If the cap is good, you should see lots
of charge and discharge current (that is, a low R value for both
connections). If it isn't, you'll see a high value. Looking at one
compared to the others will make the bad one stick out like a sore
thumb.
To quiet a noisy transformer, he says they shove a non-conductive
shim between the windings and each side of the transformer core.
I've got a noisy one, and I'm going to do that.
One other point of information. R2 on the power supply rectifier
board is shown on the schematic as 470 ohms. For a while, they were
building them with a 20 ohm 25W resistor. He said it is now 10 ohms
25 watts. The resistor is part of a surge protection circuit.
73,
Jim Brown K9YC
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