Hi all,
Firstly sorry if I have posted this in the wrong area was tossing up to post in the power supply space, never the less.
I have a perplexing issue in my current build (2x EL84 PP Guitar amp). I have about 50VAC in the 260V DC OPT center tap. (this DC voltage a little lower than it should be but i am running through a light bulb at the moment)
The design itself is very common, the secondary of the PT is being rectified by a EZ81 this DC is being filtered by a 32uF cap. At this point the OPT center tap is connected.
I have considered magnetic interference, by my scope trace doesn't resemble a sine (AC) wave as I would expect. It looks like a sine wave with the negative side flattening at 0.
I have considered a faulty cap, and connected another in parallel to see its effect... none at all still the same trace.
Something I haven't measured that comes to mind as I write, is the frequency of this half sine wave (rookie mistake)
I would be very grateful for ideas/experience/wisdom/sage advice that you might be able to share.
Firstly sorry if I have posted this in the wrong area was tossing up to post in the power supply space, never the less.
I have a perplexing issue in my current build (2x EL84 PP Guitar amp). I have about 50VAC in the 260V DC OPT center tap. (this DC voltage a little lower than it should be but i am running through a light bulb at the moment)
The design itself is very common, the secondary of the PT is being rectified by a EZ81 this DC is being filtered by a 32uF cap. At this point the OPT center tap is connected.
I have considered magnetic interference, by my scope trace doesn't resemble a sine (AC) wave as I would expect. It looks like a sine wave with the negative side flattening at 0.
I have considered a faulty cap, and connected another in parallel to see its effect... none at all still the same trace.
Something I haven't measured that comes to mind as I write, is the frequency of this half sine wave (rookie mistake)
I would be very grateful for ideas/experience/wisdom/sage advice that you might be able to share.
Is this under static conditions or while playing - i.e. are you running a signal through it?
So the signal is clipped. I would check the capacitors between the driver tubes and the output EL84.
Additionally, remove one set of EL84s and see if there is any change in the AC signal. Repeat for the other set of output tubes.
P.S. does the circuit include a signal balance adjust pot? A schematic would help.
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Hi thanks for replying, regarding the input there is no signal in fact I have lifted the inputs of the phase splitter to isolate this section. I will put up a schematic as requested as soon as I get a minute to do so. I think you are correct it’s hard to discuss without this.
Cheers
Cheers
Moved to Instruments and Amps per forum policy.
One possible explanation of your symptoms is that half of your rectifier valve is not contributing properly. Confirm for yourself that both anodes are receiving equal and appropriate voltages. Then try replacing the valve with another, or, just for the test, with 1N4007 diodes.
All good fortune,
Chris
All good fortune,
Chris
Yes.
Unless confirmed otherwise I expect it to be ripple on your +V rail.
Since tube rectifiers are very limited as of current capability, very small +V caps are used which of course increases the problem.
And if for some reason (miswiring?) one half of the rectifier is not working, you effectively have a half wave rectifier, the worst of all possible.
Unless confirmed otherwise I expect it to be ripple on your +V rail.
Since tube rectifiers are very limited as of current capability, very small +V caps are used which of course increases the problem.
And if for some reason (miswiring?) one half of the rectifier is not working, you effectively have a half wave rectifier, the worst of all possible.