JCM 800 Standby off = loud pop

[Freebird]

Howdy!

I got a JCM 800 Model 2210 from around 1989, which has two channels clean/distortion and a spring reverb. After playing the amp and if you then switch-off standby, it often gives a loud pop. I know, heard and read that is very common for Marshall amps. Nonetheless I tried to figure out, how it can be eliminated.

Altough I replaced with a new standby switch, it does still pop.

Altough I replaced the four rectifier diodes 1N4007 with four UF5408. See picture https://www.dropbox.com/s/lb3hmohmo4qk6 ... 8.JPG?dl=0

From what I understand is, that if you switch-off the standby, after there is a induction voltage, which makes the poping noise. Question: Is it possible to reduce this behavoir with a freewheeling diode (in German Freilaufdiode)? Don't know exactly how you say it in english. If yes, has anybody experince with this in Marshall tube amps?

Thanks in advance for any advice or idea.

Daniel

[alexradium]

you can reduce the pop with a capacitor and maybe a resistor in series,across each contact,its not an exact science,start with a 47nF/600V and hear what it does.

[Freebird]

Thank you for your hint. In the meantime the customer took the amp back. I told him that it is normal with certain Marshall amps.

Daniel