POP when switching channels

[Valvehead]

Are there any common mods to cure this? Amp switches channels via push/pull pot and a relay. Pretty loud pop when switching.
The amp maker knows about this but wont offer any help and a schematic is out of the question . But offered to upgrade the switching if i ship the amp to him.......almost $700 !!

I do see theres 35vdc at the pot switch .. heres a pic of the relay and i dont see anything else on the board as far as an optocoupler , etc...

anything i can try ?

[Jazz P Bass]

What amp is it.
Put that info up so all can see how helpful they are.

[Valvehead]

What amp is it.
Put that info up so all can see how helpful they are.

1996 Wizard 100 watt head

[nosaj]

1996 Wizard 100 watt head

This one in the link for 4800?

geezz

[nosaj]

It seems there are several models and there are some schematics out there.
Need a specific model.
nosaj

[Valvehead]

Modern classic 1 , 100w , single input , made in 96

[nosaj]

Modern classic 1 , 100w , single input , made in 96

Can't find anything on that. maybe enough info can be inferred from the modern classic 2 link I posted.

nosaj

[Jazz P Bass]

From what I can see in either schematic, the relay input comes off of a ,02 blocking capacitor.
Check to see that that cap is good and Not passing Vdc to the relay.
If the cap is bad and passing Vdc , well, right there is a possible source of 'popping'.

[Valvehead]

From what I can see in either schematic, the relay input comes off of a ,02 blocking capacitor.
Check to see that that cap is good and Not passing Vdc to the relay.
If the cap is bad and passing Vdc , well, right there is a possible source of 'popping'.

not passing dc

[nickb]

If it's like the schematic shown, the switching on the grid of V3b is a potential ( pun not intended) problem. There is always a small grid leak current which will develop a voltage over whatever resistance is present in the grid circuit. When the relay changes that resistance can also change resulting in a pop.

Try this, not perfect but it should do.
1. Add a 10nF in between the relay and the grid of V3b
2. Change the 2,2meg to 470k
3. Disconnect the 470k that goes to ground that is located after the rhythm master pot.

[Valvehead]

If it's like the schematic shown, the switching on the grid of V3b is a potential ( pun not indented) problem. There is always a small grid leak current which will develop a voltage over whatever resistance is present in the grid circuit. When the relay changes that resistance can also change resulting in a pop.

Try this, not perfect but it should do.
1. Add a 10nF in between the relay and the grid of V3b
2. Change the 2,2meg to 470k
3. Disconnect the 470k that goes to ground that is located after the rhythm master pot.

i dont think that scem is accurate..... #2 and #3 you listed are not in the amp..i went over the whole board

[nosaj]

i dont think that scem is accurate..... #2 and #3 you listed are not in the amp..i went over the whole board

Can you draw one up for us then since you have it in hand?
nosaj

[Valvehead]

Can you draw one up for us then since you have it in hand?
nosaj

no time.........if it helps , it does this with ALL volumes on 0

[nosaj]

Well thats no help at all. You say the schem isn't right. And you don't have time to help us help you. Sounds like a done deal..

nosaj

[pdf64]

Does the relay coil have a diode across it in very close proximity, to kill the spike?
Is the supply for the relay adequately decoupled?
Are you sure that the 0V common of the relay isn’t contaminating the signal 0V?