JCDenton6
Well-known member
Anyone have an idea of how hot EL34's run on bold power settings with silicon diodes? I don't have a probe.
2 of 3 Rectifier tubes went south on me today.
2 of 3 Rectifier tubes went south on me today.
Bias question inside.
- Thread starter JCDenton6
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Third Age Amps
Well-known member
Have you modded the Bias? If not, you probably have a component failing. If you have, read on!
With the chassis out, check across any Power tube pin 3 (+) to ground (-) with your meter on DCV. That will give you the Plate voltage. Then divide the tube's maximum wattage (Power) rating by that voltage reading. Let's say you read 380V at pin 3. 25/380 = .066. You then multiply that answer by .7. .066*.7 = .046. That (.046) is what you should set your bias to.
(WATTS/PLATE VOLTAGE)*.7 = Bias Voltage
With the chassis out, check across any Power tube pin 3 (+) to ground (-) with your meter on DCV. That will give you the Plate voltage. Then divide the tube's maximum wattage (Power) rating by that voltage reading. Let's say you read 380V at pin 3. 25/380 = .066. You then multiply that answer by .7. .066*.7 = .046. That (.046) is what you should set your bias to.
(WATTS/PLATE VOLTAGE)*.7 = Bias Voltage
JCDenton6
Well-known member
Ah ok, gotcha! I'll have to borrow a meter soon.
I have not modded the bias yet, but I know that the 2 rectifier tubes that failed were in the amp since the original owner bought it back in late 99' (big bottle tubes)
I'm running the amp on spongy/diodes for now.
I have not modded the bias yet, but I know that the 2 rectifier tubes that failed were in the amp since the original owner bought it back in late 99' (big bottle tubes)
I'm running the amp on spongy/diodes for now.
