VVR guidance in Tweed Champ

[Colossal]

You zapped yourself twice

If that is really true then my belief is that your method of working inside a tube amps is WAY too casual... The first shock should have been enough of a warning but allowing it to happen twice on the same project is bad practise...

Yeah, I think he had the back cover off the amp and was groping around blindly looking for the VVR knob and found a live lead instead. Good way to die.

[bretschwartz]

[quote="sliberty"]Normally you would put the board in between the first filter and the plates (OT). But since a PCB was used and the first filter is on the board this would require lifting the positive side of the first filter from the board and connecting to this now loose end.

Lift the two red wires from rectifier pin 8.
Lift the positive end of the 22uF cap off of the PCB. Make a small loop with this loose end to connect a new wire through.
Run a new red wire from rectifier pin 8 to the B+ In on the VVR.
Run a new red wire from rectifier pin 8 to the loop on the positive filter cap lead.
Run a new red wire from the two lifted wires to the B+ Out on the VVR.

Steve,
Above were your directions for the tweed champ which worked like a charm. I'me also building a tweed deluxe also with PCB board and the VVR isn't working.

Can you tell me if my connections should work?

- I removed the standby switch completely and removed both red wires. One was going to the rectifier pin 8 and the other to the B+ on PCB (both removed)

- As in your champ directions, I lifted the positive side of the 22uf/500v cap and attached a wire to lifted end of cap and attached to rectifier pin #8.

-I ran a new wire from rectifier pin #8 to the B+ "IN" on the VVR

- I ran new wire from lifted B+ on PCB and ran it to the "OUT" on the VVR

When I powered up the amp itself worked perfect, but when I adjusted the VVR there was no change at all. If my connections are correct, then I'me thinking its a VVR problem.

thanks for the help
Bret


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[UR12]

Remove the wire on the B+ out on the VVR and carefułly check the voltage at B+ out on the vvr board while adjusting the VVR pot. If it doesnt vary
The voltage from full to 10% B+ then there is a problem with the
VVR most likely the MOSFET. If you change the MOSFET make
sure you also change the Zener diode on the board just in case
It is also bad. If the voltage does vary then the VVR is working
Correctly and you have a problem somewhere else. If the VVR checks
out fine, with the wire still disconnected from the VVR B+ out, check
the voltage on the board where you removed the positive side of the cap.
In other words if the amp still works with the B+ out disconnected on the VVR
Then you have a wiring problem. Do you have any pics?

[bretschwartz]

Remove the wire on the B+ out on the VVR and carefułly check the voltage at B+ out on the vvr board while adjusting the VVR pot. If it doesnt vary
The voltage from full to 10% B+ then there is a problem with the
VVR most likely the MOSFET. If you change the MOSFET make
sure you also change the Zener diode on the board just in case
It is also bad. If the voltage does vary then the VVR is working
Correctly and you have a problem somewhere else. If the VVR checks
out fine, with the wire still disconnected from the VVR B+ out, check
the voltage on the board where you removed the positive side of the cap.
In other words if the amp still works with the B+ out disconnected on the VVR
Then you have a wiring problem. Do you have any pics?

I Removed the B+ out wire and powered the amp up. Put my meter on B+ out of the VVR and couldn't get a reading. The multimeter was jumping all over the place going from 500v down to 32v and continuously changing to a point that its unreadable. My meter is auto ranging but I also tested with another meter with the same results. So I'm assuming the VVR crapped out.

[UR12]

What do you measure on the b+ in on the VVR. Also check your ground on the vvr

[bretschwartz]

What do you measure on the b+ in on the VVR. Also check your ground on the vvr

I already have the VVR our of the amp but if mem serves me it was around 501 volts or something close to that. It was a solid steady reading.

Dana,

assuming the next VVR that I just ordered is working (which i'me sure it will), was my wiring that I showed on the layout correct for the VVR?

thanks
Bret

[UR12]

What do you measure on the b+ in on the VVR. Also check your ground on the vvr

I already have the VVR our of the amp but if mem serves me it was around 501 volts or something close to that. It was a solid steady reading.

Dana,

assuming the next VVR that I just ordered is working (which i'me sure it will), was my wiring that I showed on the layout correct for the VVR?

thanks
Bret

Yes it looks fine. The symptoms that you describe all sound like a bad ground on the VVR board to chassis ground.

[bretschwartz]

What do you measure on the b+ in on the VVR. Also check your ground on the vvr

I already have the VVR our of the amp but if mem serves me it was around 501 volts or something close to that. It was a solid steady reading.

Dana,

assuming the next VVR that I just ordered is working (which i'me sure it will), was my wiring that I showed on the layout correct for the VVR?

thanks
Bret

Yes it looks fine. The symptoms that you describe all sound like a bad ground on the VVR board to chassis ground.

Dana,

I just pulled a working VVR from my kids amp and popped it in the tweed deluxe and its working like a charm. My memory was a little off as the incoming voltage was 371 volts (not 501)and the output was adjusting exactly like you said as I turn the knob.

thanks for your help!

Bret