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Valvepower · 16th Aug 2022, 10:09 am

Bill,

I pretty much look as if it’s all been covered.

I agree dropping the HT if nothing else comes to light as regards mains voltage setting etc. Personally I’d investigate fitting a resistor in between 100 and 220 Ohm in series with the 5Y3 anodes (pin4-6) off the top of my head it would need to be at least a 5 to 7 watt part as it will dissipating quite a lot of power. These need to be securely mounted on a tag panel or strip.

I had a similar issue with an Push Pull EL84 amplifier build where the HT was too high and EL84 anodes were too far the wrong side of 300V.

Sounds if you have intermittent joint somewhere possibly a solder joint or valve base connection. In a recent restoration of a Clavioline I came upon a dodgy joint that had been there since it was first made in 1963!

I had to explain the basics of a Tremolo circuit for a future BVWS article on an 'odd-ball' guitar amplifier and it was interesting to see the You Toob video.

Regards
Terry

16th Aug 2022, 10:09 am	#32
Valvepower Octode Join Date: Aug 2008 Location: Rayleigh near Southend-On-Sea, Essex, UK. Posts: 1,883	Re: Fender Vibro Champ Amp Bill, I pretty much look as if it’s all been covered. I agree dropping the HT if nothing else comes to light as regards mains voltage setting etc. Personally I’d investigate fitting a resistor in between 100 and 220 Ohm in series with the 5Y3 anodes (pin4-6) off the top of my head it would need to be at least a 5 to 7 watt part as it will dissipating quite a lot of power. These need to be securely mounted on a tag panel or strip. I had a similar issue with an Push Pull EL84 amplifier build where the HT was too high and EL84 anodes were too far the wrong side of 300V. Sounds if you have intermittent joint somewhere possibly a solder joint or valve base connection. In a recent restoration of a Clavioline I came upon a dodgy joint that had been there since it was first made in 1963! I had to explain the basics of a Tremolo circuit for a future BVWS article on an 'odd-ball' guitar amplifier and it was interesting to see the You Toob video. Regards Terry Last edited by Valvepower; 16th Aug 2022 at 10:19 am.