F 30 No sound

[Sicman71]

Hello all. I need some help. My F30 seems to power on. The tubes glow. s bit of sound comes out of the speaker. But, the light on the front panel does not light up. And, there is no sound when playing through the amp. I did notice a few times in the past, the power switch didn't seem to turn the light on.

Thank you all.
Scott

 

[domct203]

This is usually a preamp tube issue.

Does flipping the speaker mute switch do anything?

Dom

 

[Sicman71]

No sir..... After more inspections, I see that V1 and V2 aren't glowing, or hot.

 

[Sicman71]

Sorry also, the front led is not lit either.

 

[Sicman71]

I replaced V1 and V2. Same issue. I don't understand why the front power led has to do with preamp valves 1 and 2?

Thanks for replying earlier.

 

[domct203]

V1 & V2 use DC heaters which share the rectification circuit with the pilot lamp. My guess is that there is a failed diode in that circuit.

Dom

 

[Sicman71]

Thanks Dom. I was just looking at a similar schematic. Can you circle the diode on that picture? I may have found something interesting.

 

[Sicman71]

I think these are the diodes.... Seems a bit brown around them.

 

[domct203]

I think these are the diodes.... Seems a bit brown around them.

That looks like the circuit. Is that on a separate pc board over by the power transformer?

Yes, that yellow wire’s connection point seems a bit shoddy, I can’t tell if that cap failed or if it was burnt from the soldering iron.

Dom

 

[Sicman71]

Right! I just got of the phone with my tech.... He'll be fixing it at some point. Hopefully soon. He is a busy man around here. He's super good. Just wish there were more techs like him. I wish I knew more. Anyway, thank YOU so much for taking the time. Rock on!

 

[domct203]

Always happy to help.

Good luck!

Dom

 

[Amptech]

Had the same problem on an Express 5:50.. check that C3 isn't shorted..