[TMC] This darn amp

[Gary Schafer]

Check that your screen voltage at the socket is holding steady as you drive it. Could be a high resistance in the supply circuit.

What is your plate idle and screen idle current?

Also check the band switch, may be the TANK is way off frequency.
Do you get any dip in plate current when you turn the plate tune cap?

Shorted output padder cap?
Do you get a peak in output power when tuning the plate tune cap?

73 
Gary. K4FMX


Sent from my iPhone

> On Oct 19, 2021, at 10:31 AM, Chris Bolkan <bolkyboats at gmail.com> wrote:
> 
> Hi TMC lovers!
> 
> 
> Got the power supply corrected. Now puts out a nice solid 360V to the final
> screens and all other voltages are correct.
> 
> The good: All voltages correct, finals now bias nicely just as I think they
> should and it tunes up nicely.
> 
> The bad: At 240ma plate current, single tone with a drive of 20, it puts
> out 120V p-p into a 50 ohm load. That calculates out to 35 watts RMS and is
> almost exactly what the inline wattmeter shows. Even when I pump it up to
> over 300ma it only puts out just 50-70 watts. I don't like doing that for
> long as occasionally the breaker trips because I have it set conservatively
> until I figure out what is wrong.
> 
> So correcting the screen voltage and making it all "right" still did not
> change the output power. That's what it was before even with what I
> consider a profound change.
> 
> This is also puzzling: There is no change in screen current (on the meter)
> no matter what I am doing tuning this thing up. The meter reads very close
> to 0 (about a third of the way up the scale as it should, but nothing I do
> changes screen current. I verified the proper screen voltage on the final
> tube socket pins so I know the sockets are not shorted. Since the screens
> get their voltage off the measurement divider, if the current is changing
> it should register.
> 
> I still have not checked the capacitance on the screen pins of the sockets
> yet. If those were somehow low would that have a degenerative feedback
> effect? Even so it seems highly unlikely that both sockets have failed in
> exactly the same way. This is so confusing.
> 
> I've been posting a bit lately about my PAL 350. I've not seen a single
> comment so I guess I don't know if the posts are even going out. Well,
> here's the latest. Any ideas would be greatly appreciated!
> 
> Chris
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