2. amps-preamps
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Variac Variable Transformer

I have a number of tube amps and tube preamps. Many are stored for a long time. Quicksilver recommends I hook up a Variac Transformer to the amps and bring up the voltage slowly and let it stay at 120 volts for ten minutes. Same process for tube preamps. I was wondering if other Audiogon members do this? I'm thinking solid state amps and preamps would be included as well...
exocet954

Showing 2 responses by kijanki

kijanki's avatar
kijanki
4,453 posts
 
It's a problem with electrolytic caps. Layer of aluminum oxide that serves as isolator diminishes over time (years) without voltage and capacitor looses its voltage rating. Applying voltage and keeping voltage at lower levels (for days) will replenish layer of aluminum oxide and capacitors will be OK. Applying full voltage to unit that was in storage for many years can cause capacitor short, thermal build-up and even explosion. Capacitors have fuse (vent) to prevent it (explosion) but it's wise to to test it.
kijanki's avatar
kijanki
4,453 posts
 
I agree with Commcat. I found rule of thumb on the internet to apply 5 min. plus 1 min for every month of storage. This would call for 41 min of reforming unit stored for three years. It seems too short and I would do this at least for many hours (if not days). Be patient.

Dekay - similar problem with SMPS power supplies. They will produce full output voltage (regulated) as soon as supply voltage crosses some threshold.
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