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5f1 champ plate voltage

2/9/2003 5:30 PM
koolaide 5f1 champ plate voltage
I have a homebrew 5f1 tweed champ-built from a kit from clark amps-sounds great..., but the plate voltage is 391v on a 6v6 gt. current checked w/ transformer shunt method is 36ma. this(the voltage) seems high and based on tub data the plate v max is 350 -is this a real problem or not? and whats the soultion?  
my electroncis knowledge is minimal-it'been a big learning curve.  
2/28/2003 1:16 AM
Bob R
According to your data, it looks like you're running that tube at about 14W. A little high (should be around 12W). You'll run through tubes a little faster but it probably sounds great. If you want to lower your plate current a little, raise the value of your cathode resistor slightly (say to 510 if you presently have a 470 in there).
2/28/2003 9:28 PM
Bruce /Mission Amps

I think it sounds better to lower the plate and screen voltage a little and keep the idle current higher so the tube is still arund 12-14 watts.  
3/7/2003 11:17 PM
bob predaina
i'm no expert, but are you running an authentic reproduction transformer off of a 123 vac power source? if so that could explain why your voltages are so high.  
maybe the solution would be to just use a variac to bring your line voltages down to 110, and everything may fall into spec. IIRC, the 5F1 had plate voltages around 340-350VDC. at 391 vdc, I'd guess that the tubes would sound brighter, and that the tonality woule be alot more like a SF champ.

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