Firing up old tube amps. Should I worry?

This is the P/P EL34 type tube amp.

Electrolytic capacitors deform over time when not exposed to voltage. The oxide layer that forms the dielectric slowly dissolves. Capacitors that wee rated at 450 working volts when new might only be able to handle a fraction of that after 15 years unused.

It is also possible for the electrolytic capacitors to dry out over time.

Best advice is to inspect them for bulges or leaks, then use a variac to raise the voltage slowly and give the capacitors time to re-form.

Buy a cheap pair of speakers from Best Buy, stand back, put some safety glasses on, flip the switch and use the return policy.

why Best Buy you can buy used car speakers from autowreck yard for $4 pair and connect them.

Don't say FIRE up
Alan

Find a repair shop with a variac or buy an inexpensive one. There is a good chance you will need it again in the future.

99% it's safe to turn them on.
I believe that this amp has good quality old school parts and despite it's better off recapped it should work.
Don't be paranoid.

The amp should NOT be powered up unless you monitor voltage while running the amp up on a variac. Either buy a variac, or bring it to a tech who can do that for you. If you value the amp, start it up that way especially if the company is no longer in business and replacement parts may not be available. I do that with equipment that hasn't been run in 5 years as well...

Agreed bring them up using a variac.

Thanks for all your input. I'm running the left channel right now on a cheapo computer speaker. Seems fine, no weird popping noises or buzzing at start up. I think I'm in the clear on this one. I'm going to run it for about 15 minutes, shut it down and then do the same to the right monoblock.

Fingers crossed.

It is always risky with equipment that hasn't been used for some time.

Right channel works normally too. I'll try not to let another 10 years pass before I run them!

I hope you had speakers connected to the amps when you turned them on.

I did. They're monoblocks, so I had the speaker connected to the one I turned on.

Really pleased and surprised at how quiet these amps are after sitting so long. Was expecting some hums or buzzes. Really a nice warm sound with a good amount of punch.

This was a World Audio Design KEL-80 kit amp that I built back in the late 90's. Not even sure if they're still around.

Never heard of it. What output tube?

4 x EL-34 per channel, driven by a 6AU6 and a 5687.

Just take the equipment out in the driveway, put it up on cinder blocks, connect to the oldest and funkiest speakers you have, wear safety glasses, and have a non-liquid CO2 fire extinguisher ready to hand. No worries...

If you wait until the 4th of July to do this, you get extra credit for any sparks which may be produced during the process.

For a bit of a preview, go to YouTube and run a search for *4000W Tesla coil test" or "Vanguard (Flopnik)."

They just may not work...

Best advice is to inspect them for bulges or leaks, then use a variac to raise the voltage slowly and give the capacitors time to re-form.

They won't have bulges if they've been sitting.

The traditional means for reforming/testing the filter caps is to remove all the tubes, and then put an incandescent light bulb of about 40-50 watts in series with the power plug. If the caps want to draw current (and thus in time overheat, which is Bad) they'll light up the bulb. This prevents the caps being damaged. When the bulb does not light, you're all set to go.

Otherwise you do run the risk of the caps failing, and they can take out the power transformer with them.


So don't run the amps unless you've done something about this!