My Randall RG50TC recently died, and before I take it to a tech I want to make sure that nothing simple/obvious is wrong with it.

The power light comes on, and so do the channel indicators, but their is no sound.

I have tried swapping out all the valves, but still no sound.

I tried plugging into the effects loop return, no sound.

I ran a cable from the effects loop send out to another amp (combo), and I got some hum, but that was it.

I tried using a different speaker cabinet and their was a faint hum, nothing else.

Did I miss out any troubleshooting stuff?

And does anyone want to take a shot at diagnosis?

Thanks in advance guys.

I'm not familiar with the Randall RG50TC but if your tubes aren't lighting it means that there is something wrong with the fillament heater circuit. It may be as simple as an internal fuse or a burnt wire, but if you have checked the externally available fuse(s) [NB. I'm assuming that if the mains fuse had blown you wouldn't get the indicator lamps lighting but stranger things...], then it is time for the tech.

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The indicator lamps don't light with the mains fuse out, as after checking it, I forgot to put it back in.

Now I just need to find a tech that isn't 3 hours drive away...

Don't kill yourself but you could get a schematic and meter out the 6v filament supply line. Hopefully you haven't blown a power trans former. I repeat though, if you are clueless with no electronics background, take it to a tech.

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Stage Guitars: '80s Thin line LP Custom, '70 LP Standard, '83 Squier Black Headstock Strat w/ Dan Torres pickups, '59 Black Danelectro DC, sometimes others.

Pedal Board: Nady UHF 10 -> TU2 -> Rocktron Big Crush -> 70s MXR Phase 100 -> Cry Baby -> Bad Monkey -> Early '80s Rat -> Early '80s Ibanez CS 9 -> Ibanez DE 7 -> Behringer Dr 100 Stereo Reverb

Stage amps: '63 Blonde Tremolux w/ two original 2X10 cabinets with a '60 Ampeg Rocket/18 watt VTB Marshall clone/ Epi VJ into a Mashall 1965A

I know some stuff about electronics as I fix my own pedals and things, and I know how to drain the caps etc, but I can't actually get the amp open.
The screws holding in the boards are ridiculously tight and won't unscrew, and I think I'd have to remove the reverb tank as well, which I can't get to without taking out the speaker...



I guess a tech would have some difficulty with that too which ramps up the repair cost...

Duh..to take something apart you have to take it apart. It is not uncommon to have to remove the speaker(s) in a combo to service the amp. As far as the screws go, they may have loctite on them. Use a new good quality screwdriver with the correct head. It may help to very slightly tighten the screw first to break the bond then unscrew it. Most techs use a long shank screwdriver because you can get in deep and spin it easily. You may have somethng very simple going on. A bad switch,an open current limiting resistor, or a bad connection could be the problem. Also something more expensive like a power tranny. Give it a good visual inspection, then break out the schematic and a multimeter. Take your time. Be patient.

__________________
Stage Guitars: '80s Thin line LP Custom, '70 LP Standard, '83 Squier Black Headstock Strat w/ Dan Torres pickups, '59 Black Danelectro DC, sometimes others.

Pedal Board: Nady UHF 10 -> TU2 -> Rocktron Big Crush -> 70s MXR Phase 100 -> Cry Baby -> Bad Monkey -> Early '80s Rat -> Early '80s Ibanez CS 9 -> Ibanez DE 7 -> Behringer Dr 100 Stereo Reverb

Stage amps: '63 Blonde Tremolux w/ two original 2X10 cabinets with a '60 Ampeg Rocket/18 watt VTB Marshall clone/ Epi VJ into a Mashall 1965A