Tim Freeze wrote:
I just bought a 30L-1 at a local auction.

It puts out 500 watts on 3.5 MHz and 7.2 MHz

On 14.5 MHz it's 350 Watts.

On 21.2 and 28.25 MHz its 200 Watts.

Any thoughts on where to start trouble-shooting?

There's not much inside there. I'd start by checking the finals to make
sure they are good, and then I'd start doing simple in-circuit checks on the
plate and screen resistors to make sure the thing isn't getting misbiased.
Those are common failure points.

Before doing anything else I would replace the power cord and wire it so the
hot lead is on the fuse and switch side (which was not the case for most
original installs) and if you are running it on 240V, add additional fusing.

I would check the 1800V lead with a proper high voltage probe. I would also
check the -170VDC supply and the filament supply to make sure they are within
a reasonable range; you can check the filament supply with it idling.

If you haven't replaced every damn electrolytic yet, now would be a good time.

I'm thinking of checking the bias voltage and working from there.

Check ALL voltages. But check for baked resistors too.

I've ordered the power supply HV upgrade kit since the caps are old and this amp has sat for many years.

I'd replace the .01uF RF trap capacitors on the AC input with modern X1 types
too, just for safety.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."