Early Marshall 1987/Tremolo Standby Snubber Caps....?

[acorkos]

This amp has one original .22uF/1000V snubber cap....between the standby switch/rectifier diodes and ground. The other is a replacement consisting of 2 x .47uF/600V caps in series stabilized by some black silicon goo.

Are 1000V caps necessary in this position, or will 630V caps work?

Thanks for your help!

http://www.drtube.com/schematics/marshall/1987tu.gif

[Mars Amp Repair]

hello Acorkos,
I suppose the 1KV rating is to handle the back EMF of the xformer windings when the standby switch is set from 'operate' to 'standby'. The arc can actually jump across the switch contacts.

You have the potential of 2 times the voltage that is across the secondary hitting those caps...so, I would say 1KV is what you need.

You can attain this by putting 2ea 0.47 caps at 600V each in series (a common orange drop value). This doubles the resultant voltage handling capability & will 1/2 the capacitance value to around .44uf.

In this application I wouldn't worry about divider resistors across the caps.

glen