Wangs VT-15 no power tube bias voltage

[bw1985]

Hi all!

Looking for help or anyone with a schematic for a Wangs VT-15 tube head.

I am not seeing any bias voltage on pin 2 of the EL84 and am a bit stumped. Can’t find a schematic for this amp, so if anyone has a copy that would be fantastic!

Thanks!!
-B

[glebert]

I think EL-84s are often cathode biased, so you wouldn't see a voltage on the grid pin. Is there a power resistor from the cathode to ground?

[bw1985]

I think EL-84s are often cathode biased, so you wouldn't see a voltage on the grid pin. Is there a power resistor from the cathode to ground?

yes there is a 120ohm 5W resistor (that I have replaced already) from cathodes to ground.

the main issue is that one power tube is red plating, so perhaps I’m looking in the wrong place.

any advice would be appreciated!

[glebert]

Have you tried a different power tube?

[bw1985]

Have you tried a different power tube?

Wow….just swapped out an EL84 and the amp is fine. Kind of embarrassing but hey I’m owning it! I guess my resistor swap fixed it the amp (the original was probably 2W and burned up).

[glebert]

Wow….just swapped out an EL84 and the amp is fine. Kind of embarrassing but hey I’m owning it! I guess my resistor swap fixed it the amp (the original was probably 2W and burned up).

Personally I try to limit myself to three or four embarrassing mistakes a day. It is all a learning process, glad the amp is working.

[The Dude]

It was likely a defective tube that took out the cathode resistor in the first place.