[TMC] Friday PAL 350 update

[Francesco Ledda]

I can test your tubes. Where are you located?

Best, Francesco K5URG

Sent from my iPad

> On Oct 22, 2021, at 18:22, Chris Bolkan <bolkyboats at gmail.com> wrote:
> 
> Hi TMC lovers!
> 
> I reassembled the amplifier after verifying that the screen grid bypass
> capacitors are good. Powered it up to make sure everything still works and
> it does.
> 
> I tuned it up at 3.9 Mhz into a 50 ohm load. Tuned the drive to 3.9 mhz ,
> then applied HV. Dipped the plate current with tune and peaked output with
> load as drive was increased. Did this until plate current was 240 ma. At
> 240 mA, power output was 50 watts, Drive level was 20, Screen grid current
> read 0.
> 
> I could probably roast weenies over the output tubes. It purrs along
> nicely........at 50 watts.
> 
> Once all tuned up I fiddled with the tune and load controls and saw
> virtually no change in screen current. This is suspicious because I would
> expect to see more happen here. But it doesn't.
> 
> Could my finals be weak? Do these symptoms align with weak finals?
> Everything seems to work so well and tunes up so nicely that I wonder if
> the tubes are weak. I'm out of other things to try.
> 
> I have no way to test these tubes because I do not have a known working amp
> to check them with. Unless someone has more ideas of something to look at,
> test or do, I am out of ideas except for testing the tubes.
> 
> Without a known good amp, is there a way I can test these tubes? If
> not.....this is a big ask, but is there someone willing to put my finals in
> their known working amp and check their condition?
> 
> Until I know the tubes are good (or not) I don't know what else I can
> try, or even if trying other things makes sense.
> 
> As always Thanks for all the help and advice.
> 
> Best regards,
> 
> Chris
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