Fender FM212r no channel switching

[nosaj]

I have a fender fm212r that had no output. I found r145 open . Tested out of circuit, subbed a 370ohm for the 330ohm and was able to get it to pass sound but not switch channels. Drive switches fine.

Can anyone help me through why it's not switching channels with the footswitch or the button on front panel.

Thanks,
Jason

[Enzo]

So look at the schematic, in the switching section, find TP20 and look at the nearby note about the test point voltages. Then see what TP20 is doing, then follow it along through U7b to TP22, and see what you find.

[nosaj]

So look at the schematic, in the switching section, find TP20 and look at the nearby note about the test point voltages. Then see what TP20 is doing, then follow it along through U7b to TP22, and see what you find.

I think also the footswitch I'm using is one I had cobbled together sometime ago using a TPS connector, the schematic looks like it is a mono connector. Anyone have an idea on building a 2 switch mono footswitch for this amp?

the controls channel switch and more drive are now working after looking at back of board and reflowing some joints. But still have to work out a footswitch if anyone can help.

Thanks jason

[Enzo]

The Fender footswitches use a plain old mono guitar cord, even the ones with five buttons.

Look at your schematic, see what gets disconnected by the jack? That is all the stuff down through D40 and D41. Duplicate that circuitry in a pedal and plug it in.

The stock pedal is 994062, and it would have LEDs in it. I don't have my pedal file with me, but I'll try to look it up when I can. I am not sure just how the LEDs were in the circuit. VOltages matter, se we can't just slap them in.

[nosaj]

Ok I cobbled this pedal together http://www.aronnelson.com/DIYFiles/up/topic79656.pdf

Now for TP20 with Footswitch
drive 2.3vdc normal 9.33v def not right

withouth footswitch using panel
drive is 2.3vdc
normal is .68vdc close but not .75vdc
my footswitch is using a green led and a red led green is ch switching if that makes up for voltage difference.

just don't know about that 9.33vdc. For some reason my thinking is leaning towards testing r119 and r121 but i can't say why.
TP22 is good
Now TP23 on Q22 voltages correct with no footswitch
normal channel switching works without footswitch

Thanks,
Jason

[g1]

The actual footswitch schematic can be seen here:
http://i227.photobucket.com/albums/d...psd89acef5.gif

[nosaj]

That could explain a lot of why it's not working. hmm, guess I'll try to get a hold of the original as I don't have some of the components.

[nap_alfa55]

try to replace D43 and D47 ( zener 10v ) and D48 and D49 ( 5.1 v zener )

[nosaj]

try to replace D43 and D47 ( zener 10v ) and D48 and D49 ( 5.1 v zener )

Replaced d43 d47 d48 d49 and u7 and once I got the footswitch resoldered the footswitch jack and all is working well now.

Thanks all


jason