Preamp causing "pop" when turning on or off

[Chazb11]

The problem is in my old JVC preamp for sure. The pop is present only when using this preamp regardless of which power amp I'm using. It happens when turning the preamp on or off, even if the volume is turned down.
This preamp is from around 1968 to 1970. Would replacing the caps in the power supply section be the place to start? Could it have anything to do with the on/off switch itself?

[Celt]

Turn the preamp on before the power amp, and turn it off after the power amp. You'll avoid the noise that way.

[avionic]

Would replacing the caps in the power supply section be the place to start? Could it have anything to do with the on/off switch itself?
Caps --doubtful,switch..remotely possible.Probably a shorted transistor or two in the muting circuit.
Turn the preamp on before the power amp, and turn it off after the power amp. You'll avoid the noise that way.Just hides the problem.:scratch2:

[Celt]

Well, what I failed to say is that some preamps pop because they have no delay relays, etc. If yours has a relay, it may be frozen.

[Chazb11]

I don't think this thing has any kind of delay circuit. It doesn't bother me that much as I can take Celt's suggestion and turn the amp off and on first. But I'm planning on selling it and would rather have it 100% for the sale.
I do have a service manual for it if anyone wants to have a look and try to figure out a likely cause.

[avguytx]

That's how I've always done the power switching on my separates and how I was always told. Preamp on first, then power amp. Power amp off first, then preamp.

[dgwojo]

That's how I've always done the power switching on my separates and how I was always told. Preamp on first, then power amp. Power amp off first, then preamp.
If you don't power up and down in this sequence with a Soundcraftsman amp it will be cooked, I know, been there done that!! Never power down the pre-amp first!! :nono:

[Celt]

Exactly. It's standard protocol.

[Paul C]

This preamp is from around 1968 to 1970.

What you are experiencing is a voltage change at output as the preamp powers up or down.

In that era, 20-30 wpc was a healthy amplifier. For such a voltage surge, as happens in your preamp, to cause a loud pop was not that much of a problem as the ampliers were not generally very powerful. It just wasn't an issue with the average audiphile's equipment in 1968, so no delay relay was built in.

There is not much you can do about it except to power up and power down in sequence as stated above. Preamp, tuner, and other equipment first, turn on amplifier last. When powering down, amp off first, then the other equipment.

[Chazb11]

Thanks everyone for the info! If it aint broke, don't fix it, it's going up for sale as is. I happen to love this preamp but I'm going to focus on my obsession with receivers and the wife will only stand so much!

[jvc_graz]

@chazb11:
can you tell me which model number you talk about? MCP-105 or VP-10(5011)?