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.

[misterc57]

Can anyone tell me if this amp is PCB or if it is turret or eyelet board?

Thank you?

[g1]

The pictures I've seen show eyelet board. (edit: that was not factory original)

[misterc57]

The pictures I've seen show eyelet board.

I have seen one pic with a turret board but I think it was a rebuild and I saw a VT-50 that was PCB.

[g1]

I have seen one pic with a turret board but I think it was a rebuild and I saw a VT-50 that was PCB.

Sorry, my mistake. I think that was a gutted and re-built with eyelet board picture I saw, with a misleading title.
These pictures with PCB look like the real thing: https://bbs.guitarschina.com/forum.p...7&pid=29954089

[misterc57]

Found this on their web site...

Two EL-84 Three 12ax7

15 watts of true tube JCM tones with 2 inputs for clean and overdrive. Clear & bright sound without being harsh…Studio level Tone so good you'll need "Jaw Insurance".

- 2x thick 100% fiberglass aeronautical quality hand soldered PCB

- VISHAY and WIMA electronics with Korean Alpha pots

- Real Leather strap

- Birch enclosure