Help with Ampeg M12

[devilsindetails]

Got an Ampeg M12 Amp in the other day. Brought it up slowly on a variac after testing all the tubes and am getting sound through Channel 1 and 2 Inputs, volume and tone pots work too.

The issue I have is that the tremolo footswitch has one loose wire and I don't know where it should be placed. In reading the Schematic I summize that one wire from the switch goes directly to Pin 3 of Valve 2 (6SL7) is this correct or incorrect?

The Trem isn't working so I am hoping that by fastening the loose footswitch wire may bring this to life as well.

I know this thing is pretty ratted up as it sits but would like to discover if the Trem is working as it sits. A complete recap etc seems in order, of course, but would be fun to see if I can get the Trem working.

Any comments or suggestions appreciated as always.

Leo

[Phil_S]

It looks like a simple switch that makes or breaks the ground connection on the cathode of one of the triodes. I don't know which section, but you should be able to tell by looking at the circuit.

[selloutrr]

Your schematic tells you. I'm confused am I missing something?

If your schematic is the correct model the foot switch as said above is a simple ground make/break. One side if the switch goes to ground the other looks to attach to the resistor connected to the C10 capacitor.

So find the V2 and visually compare the schematic to the components and find the connection point.

[jjman]

The loose wire on the pedal goes to ground. It allows the cathode resistor of the oscillator to make it's connection.

Check the coupler caps for DC leakage. The one I worked on had all red Astrons and almost all of them were leaking DC.

Great sounding trem btw. See attached PDF schematic.

[selloutrr]

From the photo it looks like the resistor has been perminantly soldered to ground and the ground wire removed. If soldered the wire along to ground doesn't fix it. Check that connection.

[jjman]

Cathode resistor looks stock to me.

Notice that 2 of the input jacks are changed. The "floating" end of the footswitch wire originally connected to one of them for ground.