Royer sdc tube mic PSU problem help....

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pucho812

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Oct 4, 2004
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O.k. I been racking my brain over this PSU for far too long and I am lost.... I built it. It is working great except for the fact I am not getting my 6 V for my heaters off the supply for my 5840 tube. I am trying to trace as to whre my screwup is. I breadboarded this with turrets and breadboard and as far as I can tell the circuit is correct. Now I am getting about 10V over my 95V and 5V short of 40 but I am not too worried about that at the moment. I am more racking my brain as to where my screw up is... Suggestions?

The Schemo is on page 2 of this PDF

http://www.diyfactory.com/projects/royerproject/royermod_2.pdf
 
What is your heater voltage measured at the positive end of C7? You apparently are getting some current flow through the tube if you are getting near 40 volts on the output coupling cap. The voltage at the cathode in a mike that uses self bias to polarize the capsule is going to be really sensitve to leakage in the capsule-grid circuit, so you should make sure all the rosin/junk is removed from these connections.
 
I am not understanding your post

voltages measured from ground at will help to understand. Using the PDF as a guide measure at

C3, C6, C7

C2, C4, C5

I would use a 100K as a B+load (100V at 100K for 1ma)
and about 40 ohms for the fil (6V/.150A) for the circuit as drawn
As a resistive test load for the Royer so you can adjust it without a tube connected
power = I^2 R or V X I to size the resistors for the load

How many amps is the transformer I like to use 2 amp 25VAC ones for my royer type supply builds

As posted by burdij make sure the microphone board connection are very clean.
 
but do you get a voltage at C6? or C3?

No load IIRC about 34VDC at C3
 
Thanks gus. PSU is away from me at the moment. Will check it after work today... It's was fresh on my mind as this morning had a tube mic on the work beach With the label, "not working" the Cuplrete was someone had managed to snap off all pins on th3 7 pin mic connector except for pin 7. No wonder it wasn't working. Now sounds good as new. But Thats one of those things you really got to work at to do something on that nature. The hardest part was putting that mic back together. What a pain to do...
 
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