kheper wrote:http://antiqueradio.org/dimbulb.htm
Disclaimer: I admit I've never paid attention to the light bulb load test descriptions that are prevalent and very, very useful.
Isn't a 40W bulb a 360 ohm resistor? A 360 ohm resistor at 400V will draw >1A. This would blow any 5AR4.
I'm confused here ...a 360 ohm resistor at 400volts?
The light bulb in on the input/AC side of the power supply transformer to limit current isn't it?
A 40watt bulb should not allow that much
voltage on primary. I wonder what
GrooveGrinder's primary and bias voltages
were when his rectifiers blew?
Isn't a 40W bulb a 360 ohm resistor? A 360 ohm resistor at 400V will draw >1A. This would blow any 5AR4.
I'm confused here ...a 360 ohm resistor at 400volts?
The light bulb in on the input/AC side of the power supply transformer to limit current isn't it?
erichayes wrote:To my knowledge, CE is the only manufacturer of high voltage FP (twist tab mount) style multi section electrolytic caps currently in production. If you find something else, like a CD or Sprague TVL, it's NOS and should be treated as such.
Should I:
1)First test the multicap for shorts, after
discharging?
2)Check the B+ to/from the 5AR4 socket
pins?
I understand that I should... and should have
check(ed) EL34 pin5 for maximum neg
voltage. With NO tubes?
Check at either EL34 pin5, and one on both
sides?
Incidently, why is it better to do the
preliminary bias test at pin 5, rather than
just full counter clockwise rotation?
Greg, did you have your DMM ground lead in a good spot?
Maybe use the chassis itself or the speaker GND.
I assume this is a 15.6 ohm stock bias
(without re-reading the whole thread I forget).
I really can see it working with those bias numbers,
so I'm guessing it was a measurement flub.
GrooveGrinder wrote:Only minor problems left are minor.
A very slight hum... barely audible.. only from
near the spkrs and not at the listening chair.
I assume due to having a 3 conductor/pronged
line cord/plug.
The preamp has one too.
Haven't bothered cheating it as its to minor
to bother... not heard whatsoever with music
playing.
And..
The bias still drifts a fair amount.
kheper wrote:Did you completely rebuild the
bias supply? It could be an old cap.
Did you replace the old selenium diode?
kheper wrote:Remove the preamp.
Use 2 rca shorting plugs.
If it still hums, the problem is inside the amp.
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