Installing Hall VVR 3 into Hot Rod Deluxe

[Xfigio]

Hi All,

Seeing as there's a fair bit of knowledge on the VVR installation on these forums, I'm hoping someone can help.

I've got the B+ connections worked out, but am totally stumped where to connect the Bias points.

I've attached a schematic, and have highlighted where the bias adjustment happens, so you at least know the vicinity I'm looking at. I had considered taking it from C-, but can't see where that hooks up to on the other side..

Any assistance would be greatly appreciated.

Also if anyone has a copy of the VVR3 installation docco, I can only find the VVR2 docco online, but have purchased the new one.

[dass101]

Your B+ connection is not correct, you need to connect the VVR circuit after the rectifier. If you want to scale the whole amp you need to insert the VVR between the diodes and the choke.

Regarding the bias connection, you insert the circuit right at C-

[UR12]

Here are the new VVR3 instructions for anyone who needs them

[Xfigio]

Hmmm, installation went well, or so I thought until test time. I'm not getting the full B+ out voltage when turned all the way up.

I get the following readings:

B+ In = 450V
B+ Out = 150V

Bias In = -47V
Bias Out = -45V I assume this is close enough to be correct.

When turned to minimum, the B+ Out goes to 41V, so about spot on.

I've confirmed all wiring is good, and that there are no paths to ground that shouldn't be there.

The only thing that's a little different with my installation is that I've got the pots separated from the board due to space restrictions. No other drama's though. The terminals on the power pot read 150V too.

My only thought was that I'd wired up the double pot wrong such that the bias pot was regulating the B+ and vice versa, though have double checked it and am pretty sure it's correct.

Another issue, is that when I put all my tubes back in, at 150V, the sound is very flubbery. It could be that there's just not enough voltage?

Only other clue is that I get the whirling and osculating when powering up, and adjusting the VVR pot. I'm prepared to put this down to the wiring, though pot to board wiring is far away from any signal path, so thought it may be worth mentioning. It could also be the B+ or bias lines though as they travel past some signal wires.

My primary concern at this point through is getting my B+ Out up to full voltage. Any ideas?

[dass101]

You should post some pics of the install, so we can check what is wrong. You get bad sound because you are operating the amp at 1/3 of B+, but with full bias, so the power stage is completely off biased.

[UR12]

If you go through the test procedures in the instructions it will have you check everything to make sure it is working properly. You should never put the tubes in until you have verified that the VVR is working properly. There are also troubleshooting tips in the back of the instructions.

[Xfigio]

Thanks for the responses.

I was putting together as much info as possible to help with the diagnosis, when I noticed on one of the photos that the VVR board has traces going to B+ on both sides. I used thicker gauge wire, and drilled out the holes, so alas both sides were no longer connected. Once I soldered both sides, all worked very well. Lovely sounds.

For future reference, and because I'd already nearly finished my build doc for diagnosis, I'll post it here for anyone else interested in VVR'ing a HRDx III.

Thanks a lot all for your help.

[dass101]

You did a great job with the document. Glad you got everything sorted out.