School me on the use of a variac

[AdamAnt316]

Very simple and clever. If I have a DMM with current reading I assume I can simple connect that in series with the live lead?

Don’t want to fry my meter.

Make sure the DMM is set to read AC volts rather than current when you connect it across the resistor. The entire idea of the resistor being there is to allow AC current to be measured using an AC voltmeter; if your DMM has an AC Current setting (most can only handle DC current), you wouldn't need the resistor at all. Once the DMM is set to read AC volts, it'll be safe to connect the probes across the 1 ohm resistor, but keep your fingers away from them.
-Adam

 

[blhagstrom]

I use a Variac to power up old tube gear in unknown condition. At around 90-100v, I usually get enough of the system charges up to get some sound which tells me things are OK to start a restore.

Past 100v, I have seen old caps start to heat and or melt down. Since a restore was intended anyway, no big deal. At least I know the iron may be good and the tubes will function to get things rolling.

I use the Variac after the tube gear recap to ease the system up. Once running at 120v, I can start to check other things as needed. I’ve caught a couple of issues on the way up through the voltage and backed off in time to make corrections.

For SS, I use a dim bulb.

I have no desire to reform caps for actual salvage and SS caps are too cheap and easy to replace to bother trying a reform saving. If they don’t regenerate from use, they get replaced. The “healing” feature of e-caps can cause them to improve from use after a long nap. But I don’t count on that much. I have experienced it on some gear though.

 

[js22]

I've just started working on old (SS) audio gear. I use a variac plugged into a Kill-a-Watt meter. (Has to be in that order or meter won't work.)

As I bring up the voltage I watch the watts reading, but also snoop around the equipment very carefully. Look for smoke, touch components (when this can be done safely!) listen, and in general try to keep all my senses engaged. Okay, maybe not taste.... And I'm always a hair trigger away from shutting power down instantly.


I wonder if a DBT would be more useful, giving a fast feedback that's easier to pay attention to than an LCD display.