Rivera troubles

[Valvehead]

Ive got a Venus 6 here , the amp works great on Ch. 2 but i have zero sound on Ch. 1 .
The venus 5 scem can be seen here : https://elektrotanya.com/?q=showresult&what=Rivera

waiting to hear back from Rivera on a 6 scem but this looks really close

Ive swapped pre tubes , measured all the pre tube pins voltages --all normal .

I did notice when probing , with Channel 1 on i have no noises at V1 /2 /3 grids..but V4/5 have signal

on Ch 2 , i have noise at all grids in the pre amp .

Could one of those "vactrol" switches cause this ? all the switching and Leds work normal..just no audio on ch 1 .

[drewl]

Hey, that looks familiar!

You have a scope?
Just follow the ch1 signal through V1 and 2.

And yes, the Vactrol LDR's can go bad.

You can hot down which ones control the channel switching and see if the correct ones are being turned on or off.

If you note which side is passing signal you could jumper across it to pass ch1 signal.

Do not jumper across the control voltage side.

[Valvehead]

no scope

what voltages should i see on the control side? the ldr 's has 4 legs..2 close together and 2 wider apart. Ill try the jumper

[drewl]

One side of the ldr will have DC voltage, that voltage will change when it is turned on or off, look at the scematic to see which ones turn on or off for channel 1.

The other side of the ldr acts like a switch and either passes signal or doesn't.

That side is usually connected by shielded cable.

[Valvehead]

Thanks..no go on jumpering each ldr. I see all of them change from about 18v to 6v or less...when i switch channels..except ph106.it stays at 18v.

[Valvehead]

well.... i tried re-seating all the multi pin connectors in the pre amp and loop pcb...that seemed to do it...Ch1 works great now .

[studiodtk5]

I have a Venus 6 with the same problem. Channel 2 is working great Channel 1 no sound or sound for a little while then no sound. I have changed the preamp tubes and disconnected and re-set the jumper cables. The tubes had no effect. The jumper cables had so me effect, but the No sound issue came back.

any other thoughts?