gm-70 help

[pre65]

John Caswell (one of the forum moderators) might look at it for you if you take it to him, but not for free.

It would be about a 95 mile drive for you. I can't think of anyone nearer.

[pre65]

Steve, do you have a multimeter, and if so are you happy to probe around inside the amp ?

[bob orbell]

Philip, maybe you should point out to Steve that very high voltages will be inside this amp. and one momentary laps may kill . BOB

[pre65]

Originally Posted by bob orbell

Philip, maybe you should point out to Steve that very high voltages will be inside this amp. and one momentary laps may kill . BOB

I hope he would already know that.

It's so difficult to diagnose valve amp problems without any accurate information and actual voltage measurements to go by.

If it were mine I'd want to find out what components had failed, and understand why, before doing any remedial work.

[Tweeky]

Hi,
I do have a multimeter and am well aware of the potentially lethal voltages when powered up. I have no desire to fry myself but would like to repair it if possible. I used John many, many years ago and would happily do so again if necessary. Main problem is the fact that I can barely lift the amp with the additional transformers for the GM-70 heaters and the Tentlab supplies are mounted on the sides and susceptible to damage during transport.

Regards

Steve

[pre65]

Can you see any evidence of "fried" components ?

[Tweeky]

Philip,

There are no signs of fried components even in the area where I saw sparking/arcing before the channel went down.

Regards

Steve

[pre65]

OK.

Are you prepared to "poke about" inside ?

If one channel is still OK you are looking to compare voltages between that and the failed channel to see where things are different.

Start with the anode and cathode volts on the driver.