[AMPS] Trouble shooting 8877 amp

[G0MJW]

> When fired up and keyed, the amp draws no plate current, and at the
> slightest hint of RF the grid current climbs and quickly trips out.  Our
> first thought was the HV had gone away, but it is still there.  I didn't
> see it, but was told there is a slight twitch or rise in the plate current
> as the grid shoots up.

Maybe the HV has gone away after all. It could be that there is some high
resistance in the circuit so as soon as you try and draw any EHT the volts
fall rapidly. A burnt out secondary might achieve this. Also check the EHT
is getting to the valve - I assume you measured it on the anode and not at
the PSU. Ians' (G3SEK) Triode board has a check for this sort of thing.

Mike


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