Hello,
As you may know from my prior post, I have a homebrew 6m 3-500Z amp that I am
trying to get to work with a Drake L-7 power supply, so far without success.
The amp has an internal power supply, with the HV disconnected. I have the B+
of Drake p/s connected directly to the same spot where the B+ from the internal
p/s had been connected, and I have the B- of the the Drake p/s connected to
chassis ground.
Using a high voltage probe, today I verified that the Drake p/s is providing
2800 vdc directly on the plate of the 3-500Z, when everything is turned on but
the PTT is not engaged. But when the PTT is engaged, even with no drive, plate
voltage immediately drops to zero.
My first thought was a B+ to B- short, but this would have caused a big bang,
and nothing is banging or smoking or doing anything unusual at all. No fuse or
circuit breaker pops. When the the PTT is pressed, a DPDT relay closes. One
side activates the T/R coaxial relay, and the other side grounds the center tap
of the filament transformer via the plate current meter. These are the only
things that happen when the PTT is engaged. In the absence of a filament to
plate short (which would have self-diagnosed with a bang), I can't imagine any
reason why pressing the PTT would cause the plate voltage to drop to zero.
Anyone have any idea at all what might be going on? It almost seems like the
Drake p/s is shutting itself off when the PTT is engaged, and then turning
itself back on when the PTT is released.
Thanks for any thoughts and 73,
Bill NZ5N
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|