[Whitestix]

I have some aging amps that I have not been powered up for a long time and have been advised that I ought to power them up slowly with a variac.  Two are SS amps and one is a tube amp.  I have searched in vain for hookup instructions on the web and have come up empty.  I assume that I have to have the amp hooked up to speakers (ie, load) before turning the amp on and slowly ramping up the voltage?  Do I need to disconnect all inputs to the amp before this process begins?  Any detailed instructions that will insure that I do this process correctly and safely will be greatly appreciated. Also, can you suggest an inexpensive variac to purchase with the appropriate amp rating?   Cheers.

[FullRangeMan]

I have some aging amps that I have not been powered up for a long time and have been advised that I ought to power them up slowly with a variac.  Two are SS amps and one is a tube amp.  I have searched in vain for hookup instructions on the web and have come up empty.  I assume that I have to have the amp hooked up to speakers (ie, load) before turning the amp on and slowly ramping up the voltage?  Do I need to disconnect all inputs to the amp before this process begins?  Any detailed instructions that will insure that I do this process correctly and safely will be greatly appreciated. Also, can you suggest an inexpensive variac to purchase with the appropriate amp rating?   Cheers.

I dont know how much watts these amps eat but I suspect a 500W Variac will do the job. Yes you have to connect the speakers to the tube amp before turn it on, transistors amps dont need speakers connected to power on, the inputs are irrelevant to this test.

I like Variacs that have a precision VU meter.
I use an Chinese JNG 500W no prob so far.

[Speedskater]

Don't use your good loudspeakers when testing or repairing amplifiers!

[Speedskater]

In stead of a Variac, you could use a 'dim bulb' / 'light bulb' tester:
https://www.diyaudio.com/community/threads/light-bulb-tester.167579/#post-2518324

Start with an old fashion 25 Watt incandescent light bulb and go to higher wattage bulbs when the bulb dims.
The problem will be finding old fashion incandescent light bulbs.

[Doublej]

Unless your amplifier has instructions that tell you not to turn it on without a speaker and/or input load present, I would start by taking the amplifier and plugging it into the Variac, with nothing connected to the inputs and nothing connected to the outputs of the amplifier. Make sure the amplifier and Variac are turned off when you do this and that the Variac is set to minimum voltage.

I would then hit the power on button/switch for the amp, wait a couple of seconds and then turn on the Variac.

I would raise the Variac voltage every couple of minutes by 25 volts, if there is no indication of a problem (no noise, smoke or burning smell). When you have it all the way to full voltage I would let it sit there for an hour. If all seems fine, power off the amplifier, turn off the Variac and turn the voltage on it down to zero.

If at any point in time something appears to be going wrong I would power off the Variac immediately.

If all appears well with the amplifier after an hour, I would unplug the amplifier form the Variac, I would then connect a source and speakers to the amplifier and plug the amplifier back into the Variac.

I would then plug the amplifier into the Variac, press the power button on the amplifier, switch on the Variac, and slowly turn up the voltage. Again if anything appears to be going wrong power off the Variac immediately, unplug everything and take the amplifier to a repair shop for evaluation.

[Speedskater]

Note that none of this will work with an amplifier that has a modern Switch Mode Power Supply (SMPS).

[richidoo]

Sorry I accidentally posted in wrong thread 

[Whitestix]

Thanks for the directions, much appreciated.