SX-680 coincidence?

[SaturationPt]

I agreed to look at a friend's SX-680s, he has two dead ones. Light up, but no output. One died a channel at a time (he told me), the other which he has owned since new, lost FM and eventually went silent.

There is voltage to the STK modules, so they're probably dead I think. But wait! There's no signal to them!

I'll get to the point. Both of them have open R401, a 33ohm resistor that supplies the 53v to the preamp. Bypass with 20ohms and they both play. I'll get a pair of 33ohm, but I wonder why both of them failed?

Anyone else worked on a 680 and found this to be the problem?

Now if I can be as lucky finding out why one has no FM, ... he might be happy enough to buy me a nice bottle of bourbon.

 

[petehall347]

change c404 just in case . then check other relevant voltages .
p.s never worked on one . i only seen the schematic .

 

[SaturationPt]

C404, I presume an el cap downstream of the resistor? Would be a good idea, I'll look at the schematic again before ordering parts.