Royer mic mod help

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Davo

Well-known member
Joined
Feb 13, 2006
Messages
504
Location
LA CA
I'm somewhat of a newbie to the world of DIY and need some suggestions with a Royer mic mod/power supply. (it's the mxl 2001 mod with the 5840 tube) I used some pdf's (uploaded by the good folks at the DIY factory) to create my pcb's, but it seems that I've gone wrong somewhere.

Having finished the power supply, I'm getting 77.9 vac from my B+ connection and 25.8 vac from the heater connection.... which should be 95v and 6v respectively. And I don't seem to have any wiring errors. Any help with troubleshooting would be greatly appreciated!!
 
Sounds like to small a VA transformer for the B+ and no load on the fil.

some math for you to do 6V fil at about .150Amps

resistor for the load 6/.150
 
Thanks Gus! I'll hook up a bigger transformer and toss a couple trimpots on there to make it easy. I appreciate the input!!
 
Don't use trim pot they will burn.

I am guessing you measure the voltages without a load?

What I meant is the fill supply needs a load to work at its correct voltage. The RC filter part of the fil supply needs a load to have voltage drops across the Rs So if you want to power the power supply up without a microphone use a 6/.150 about 40 ohm load

The watt rating would need to be > the current ^2 times the Rload .15^2 x 40 or the voltage times the current 6V x .150 .9watts so use a 1watt or bigger resistor

Use a 100K for the test B+ load, work out the watt rating

What size transformer are you using now? it might be fine.

Looking back at your first post I think maybe you are only working as a X2 not X3 voltage circuit. About 70VDC is what you get from a X2 circuit and a 24VAC transformer with no load

I would guess there is an error in the wiring or something wrong with the board. I build on perf most of the time so I have not used a PCB for the royer PS.
 
Good call! It is working at x2 voltage... as well, I've tested the transformer and it's damaged.... in the course of all my fiddling, I've had a few shorts. Ah well, back to the drawing board... and using perf board is beginning to sound like an excellent idea. Thanks Gus, I appreciate all your help!!
 

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