I got someone to look at it in late January. Turned out to be a faulty power amp valve taking things out. The rectifier arced a bit, but the smoke was from the resistor over the filter cap.

A while ago my 18w TMB stopped working. The sound went away gradually while playing it. An amp builder suggested the power valves, so I got new ones (It was about time, two years of playing it cranked). Nothing happened. I left it at a tech who said a resistor had come loose, and they fixed it. It worked for a week untill it started making very loud crackling noises, and the guitar cut in and out.

I've just opened her up to see if there's any loose resistors. There isn't so I fired her up in the hope she'd work again. Lots of crackling and the rectifier blew. Glowed whit hot and pour out smoke. Now it's black.

Is it as easy as getting a new rectifier valve, or is there an underlying problem that needs to be sorted out?

Cheers,
Al.

EDIT: The valve didn't turn black, that was just how the light was hitting it at the time.

Fair enough, most of the time the volume doesn't go above two. It's only for recording I crank it up a bit more. At the moment I've got one Wizard in the combo, and a second in a separate 1x12. I can always connect both when being loud.

No, it's a 1987 circuit.

I realise that every amp is going to vary, but is there a ball park figure to how many watts a 50w plexi will put out when dimed?

I just got a couple of Eminence Wizards, and if one isn't enough on it's own, I'll convert my combo to 2x12.

Yeah, that's probably it, not being an amp tech myself, I didn't quote him properly.

As closure to this thread I finally got around to getting this amp to a tech.

He said the bias was running at a ridiculously low voltage (mid twenties?) which is probably why the valves and HT fuse blew. Apparently there was a resistor limiting the voltage from anything over 30v, so he changed that and biased to around 35v.

I was afraid that'd be the answer.

My two main amps are out of action due to power amp valves now (the other being an 18w made from Ceriatone and other bits)

 

Hi all, new to the forum.

I bought a 1987 off a my local forum (AGGH), it's been passed around a few members, so I'm not sure of any mods and such, but I have a few questions all the same.

The day after I got it it blew a HT fuse, I emailed Nik for the correct rating/type, and got a new one. I'm not sure if this has happened before or since, but one power valve looks blown i.e bottle is white in colour and doesn't glow. The amp still works, but would it cause damage to the amp running it on only one power valve?

Also I'm interested in what bran of valves people recommend.

Cheers,
Al.