Fender FM 65

[Valvehead]

Cant find a scem for this so here goes.....

model fm65 dsp

All kinds of weird problems :

Sometimes wont switch channels , then seems to be stuck on one sound (clean?)


sometimes : ch. switch doesnt work , channel light doesnt work , NONE of the controls work , including the volumes.


Sometimes the amp powers up and works just fine


sometimes if the DSp effects are on the reverb will "swell up" real loud and turn into a huge nasty feedback / noise type of sound. To stop it , you have to power off and then on, then the amp functions perfect .

I went over the board and re-flowed a few joints , nothing looks burnt . I dont have a scem with voltages on it so i dont even no where to start on this thing

[Enzo]

Voltages won;t tell you much. It is solid state, so all the op amps will be running on the +/-15 or maybe +/-12 or whatever. The power amp will be running on the +/-20-30-40 or whatever. if functions stop working, it could indeed be loss of power supply to some chips, but if the supply is present at all, then voltages throughout the circuit will either be there or not - not likely "wrong."

Open it up, put it on the bench, connect a speaker, play a signal through it. Connect a CD player or something. Now while it is running, probe and push on the circuit boards, on the parts, on the controls, and especially on any ribbon cables or cables between subassemblies inside. When you push on something or flex a board, do the symptoms start - or stop?

Loss of chanel switching usually suggests a problem with the footswitch jack, check the solder there.

[Valvehead]

well.... after re-flowing a bunch of joints , and re-seating the Dsp chip , the amp seems to be functioning normal .

for now..........

[Enzo]

Wouldn;t be the first time that was all an amp needed. Glad it works.