[Collins] 32S-1 Oddity: advice please?

[Gerald]

On Mon, 2005-08-08 at 12:24 -0700, wb6orz wrote:
>    Interestingly, this one has too HIGH grid drive. In Tune, on all bands, and with Mic Gain only as high as 9 o'clock, the grid drive pegs the meter, and while stable there, it is quite touchy/difficult to bring down, w/o turning the Mic Gain almost back to nothing. Doesn't appear to be oscillating because the alignment of the RF section went fine, with caps that nulled properly. Before I go any further than Tune, the concern is the too high grid drive.
>     Experiences? Ideas?
>     Thanks in advance.
>     (((((73)))))
>     Les
>     ---===WB6ORZ===---

Broken ALC, probably leaky black beauty time constant capacitor or a bad
6AL5?

Oscillating PA from incorrect neutralization?

Broken meter circuit? Though I don't see much that can go wrong. The
meter is 1 ma, and the grid circuit shunt is 1K, probably makes the
meter circuit about 1.1 ma full scale. Full drive for class C would be 5
ma for two 6146 so pegging isn't yet hard on the tubes.

In SSB the grid current should barely tickle as the ALC keeps it down to
virtually zero to keep the PA tubes in class AB1 for minimum distortion.

-- 
73, Jerry, K0CQ, Technical Advisor to the CRA
All content copyright Dr. Gerald N. Johnson, electrical engineer