screen grid in a champ

[Andy Le Blanc]

Had the opportunity to work in a little silver face champ this morning.
It had many issues, it was eating tubes, the coupling cap to the 6v6 was leaking dc,
the bias resister was chard and in two pieces, the bypass cap had blown up,
and a wax stalagmite on the speaker cone revealed a blown opt.

After reworking the circuit... I checked the plate and screen grid relationship by measuring the difference between the two
and found the screen grid to be positive relative to the plate by around 2v.

I added a 1k resistor between the screen grid lug on the socket and the power rail and 220k to ground from the screen grid lug as a bleeder.

This mod brought the screens to -4v relative to the plate.

I got a feeling the screen voltage was the long term issue leading to the opt meltdown, reduced tube longevity and finally a catastrophic failure.

And whats the deal with the pop up ads in the post preview? jeez
and the final post?, is it on my end ?

[JazzGuitarGimp]

I've never seen popups on TAG.

[Andy Le Blanc]

me neither, if your not seeing them, then its on my end, very frustrating...

[Phil_S]

Pop up is your computer Andy. Sorry to hear that something crept in.

Thanks for the post on the very sad, now happy Champ.