Standby Switch squeal/bark sound on Marshall or Fender

[nsubulysses]

That is very similar to the sound I heard when powering down Mesa Boogie Triple and Dual rectifiers with volume and gain both over 5.

Never heard the extended squeel.

If you gently set the standby over to non operational mode rather than whacking it off and jostling the whole chassis does it do it? Could be wrong but I bet this is why Enzo had you unplug the amp. No mechanical vibration ie microphonic tube

[Jazz P Bass]

If the noise does not occur when unplugging the unit from the wall socker, with the amp on, then it is a switch problem.

No?

[g1]

It's a little tricky here as the chirp occurs when he switches from "play" to "standby".
Unplugging the AC cord from the wall while in play mode does not quite simulate the condition as the supply is still loaded.
From what I understand, it is the standby switch that is the issue, not the power switch.

[eschertron]

It's a little tricky here as the chirp occurs when he switches from "play" to "standby".
Unplugging the AC cord from the wall while in play mode does not quite simulate the condition as the supply is still loaded.
From what I understand, it is the standby switch that is the issue, not the power switch.

Was the experiment ever performed where the power switch was toggled OFF, while leaving the standby switch alone? Or did I miss that?

[Jazz P Bass]

Was the experiment ever performed where the power switch was toggled OFF, while leaving the standby switch alone? Or did I miss that?

Interesting thought.

I do recall having an amp where the Standby had to be left on/ Power switch off.

[nsubulysses]

This thread is more theoretical than the philosophy of tone thread.

[pdf64]

In this case a Marshall super lead 100W, a squeak like chirp is a better way to describe it if you kick the standby on (removing power) at volumes 5 and up

Sorry, I missed the model ref in post #7; does the standby interrupt the dc side, between reservoir and choke, as per the 60s arrangement, or the ac side, between winding and FWB, as per the 70s onward method?
http://bmamps.com/Schematics/marshal..._100w_1959.pdf
http://bmamps.com/Schematics/marshal..._year_1988.gif
Or maybe some other arrangement, eg between rectifier and reservoir?
Whichever, the HT seems no place for a switch, use of such a standby is pointless at best and often likely disadvantageous to reliable operation.
But at least it's not the worst standby implantation Marshall came up with http://bmamps.com/Schematics/marshal...d_50w_1987.pdf

[Ampzone]

Sorry, I missed the model ref in post #7; does the standby interrupt the dc side, between reservoir and choke, as per the 60s arrangement, or the ac side, between winding and FWB, as per the 70s onward method?
http://bmamps.com/Schematics/marshal..._100w_1959.pdf
http://bmamps.com/Schematics/marshal..._year_1988.gif
Or maybe some other arrangement, eg between rectifier and reservoir?
Whichever, the HT seems no place for a switch, use of such a standby is pointless at best and often likely disadvantageous to reliable operation.
But at least it's not the worst standby implantation Marshall came up with http://bmamps.com/Schematics/marshal...d_50w_1987.pdf

Im still on the road away from the amp, back in the AM, but yes its a standard super lead 100w Marshall.
No tube rectifier, and it has a choke. And we did try the wall power removal inatead of the switch where it was normal, no weirdness.

[Ampzone]

So, I did the tubes swap on the pre-amps, no change. I did note that if you turn the treble or mid down it gets less pronounced. Going most of the way down it goes away altogether. So the eq is playing a big part.

[Ampzone]

All the wiring around the eq looks tight.

[pdf64]

yes its a standard super lead 100w Marshall

Which schematic provided in the post #22 links best matches the amp, with particular regard to the standby arrangement?

[Ampzone]

Which schematic provided in the post #22 links best matches the amp, with particular regard to the standby arrangement?

Neither exactly, the amp does not have snubber .22uf caps to stop the standby "pop" as mentioned earlier. One leg of the 100ma choke is tied together with the OT Center Tap on the standby switch. The other side of the standby leg goes to the HT fuse/filtering. In addition the other side of the choke ties to the screen supply and 10k 2w resistor. I've seen this type of arrangement before on 60's Marshall's with ot center taps and choke going direct to the standby.

[g1]

So basically this standby arrangement, but with the fuse on the other side of the standby switch:
http://bmamps.com/Schematics/marshal..._100w_1959.pdf

[Ampzone]

So basically this standby arrangement, but with the fuse on the other side of the standby switch:
http://bmamps.com/Schematics/marshal..._100w_1959.pdf

Yes

[Ampzone]

Yes

I cannot find anything unusual, voltages look tight.