In a message dated 3/2/99 10:13:54 PM Eastern Standard Time, email@example.com
>I have changed tubes between three different amps and three different
>sets of 3-500Z's and it happens with all tubes. I am sure the problem
>is in the amp. In addition, I have checked the shunt resistors in the
>grid circuit, and they all check good.
What shunt resistors?? In an un -voodooed TL-922 there are no resistors,
just a pair of grid chokes plus 220pf caps per pin. Those original
chokes are too big, current and low resistance wise. I suggest replacing
with something in the 750uh to 1.5mH 160ma and 25 Ohms DC resistance
range...as used in the SB-220. If there are some strange parts in the
amp, it might be best to throw them away and follow the original design.
In a factory-stock TL922A there is a 470 ohm resistor in parallel with the
grid choke -actually the resistor is wrapped & soldered to the leads of the
choke. A real pain in the ass to measure each individually during
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