Safe 5e3 Bias?

[pezed]

Hello all, I just finished my first amp project, a 5e3. I used a power transformer and tubes i found from a 1950's zenith phono amp. Built the amp based on the ceriatone layout and mission amps schematic. I've found this transformer was meant for 110 volt so its running the voltages a bit high:

Plate (between pin 3 and 8): 366vdc
Cathode resistor (270ohm): 21.8v

If my calculations are correct, I'm coming up with 38ma per tube dissipating 14watts each!!
Should I increase the cathode resistor on up to 300ohm or more for safety? The tubes are not showing any signs of trouble yet. I've been playing it now for at least 10hrs over the past few days and it sounds really good, I would rather not fry my tubes too quick though!

I've also noticed my filament voltages are too high as well, running at about 7vac instead of the standard 6.3. Should this be cause for concern also?

Thanks everyone!

[Bruce / Mission Amps]

Hello all, I just finished my first amp project, a 5e3. I used a power transformer and tubes i found from a 1950's zenith phono amp. Built the amp based on the ceriatone layout and mission amps schematic. I've found this transformer was meant for 110 volt so its running the voltages a bit high:

Plate (between pin 3 and 8): 366vdc
Cathode resistor (270ohm): 21.8v

If my calculations are correct, I'm coming up with 38ma per tube dissipating 14watts each!!
Should I increase the cathode resistor on up to 300ohm or more for safety? The tubes are not showing any signs of trouble yet. I've been playing it now for at least 10hrs over the past few days and it sounds really good, I would rather not fry my tubes too quick though!

I've also noticed my filament voltages are too high as well, running at about 7vac instead of the standard 6.3. Should this be cause for concern also?

Thanks everyone!

I'd try and get the B+ down, not change the power tube's bias voltage.
What rectifier is in there now?
Yes, 7v on the filament string is a little high... you might want to use a couple .5ohm@5 watt resistors in series with the filament leads to get that lower.

[pezed]

I'm using the old 5y3GT rectifier from the old zenith phono amp. It is the original Zenith one. Heres some more voltages with the amp on (not on standby):

Tranny output: 756vac
DC output at rectifier: 399vdc
DC after the first 5.1k resistor: 359vdc.

[pezed]

Comparing my voltages to your schematic my voltages are very similar except for after the 5.1k resistor, my voltages are exactly 20 volts higher than yours (359 vs 339) I can't seem to figure out why this is happening?
could it be because i used a 3 watt resistor instead of 2 watt?

[Bruce / Mission Amps]

Comparing my voltages to your schematic my voltages are very similar except for after the 5.1k resistor, my voltages are exactly 20 volts higher than yours (359 vs 339) I can't seem to figure out why this is happening?
could it be because i used a 3 watt resistor instead of 2 watt?

Your voltages are not crazy high but what schematic of mine are you comparing to though?
No the 2 vs 3 watt value will have nothing to do with the voltage drop.

[pezed]

Heres the schematic. Actually im not certain that its even yours. I put my voltages on it in red for comparison.

thanks for your help!