Variac

Cope1

My a@# hurts!
Was curious, when you use a variac to power up say some old tube amp to test it out, what would the procedure be as far as what voltage to start at and how long for each increase? :scratch2:
 
Cope1 said:
Was curious, when you use a variac to power up say some old tube amp to test it out, what would the procedure be as far as what voltage to start at and how long for each increase? :scratch2:

I don't think there is any absolute method; just experience.

Well, I usually bring the unit up at about 35% line (approx. 40VAC). If no fuses pop. then we can let it cook for a while. Leave it at that point for a couple of hours checking for smoke, sizzle etc. During this time the electrolytics will be re-forming.

Then, if no obvious problems are apparent, kick it up to 50%. Use smaller steps as you approach full line voltage (e.g. 65%, 80%, 95%). Let the unit cook for a couple of hours at eash step.

There are several others on AK with a lot of experience doing this; I hope some of them jump in here and give us their methods.

Paul
 
I bought this Variac used and someone has marked the 40V mark with a marker, but what you said sounds good to me, Im flea marketing tomorrow and am gonna see what I can find, hey if nothing else I might get to see something blow up!! :banana: :D
 
I usually do 10v for 5 hours, and bump up 10v each evening. When it hits
100v I go real slow. 10 hours for each 10v. run it longer if the caps
especially if the power supply large can cap gets hot. The goal
here is to reform the caps.

Well worth the effort, revived (or at least didn't explode them)
5 PAS and 3 ST70s.
 
Cope,
If you get your Jap amp fixed, you can run it off the variac. Just set it to 100 volts.

- Pete
 
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