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QUESTION ABOUT VARIEAK?

Stellasarat

Stellasarat

Active Member
Sep 17, 2013
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I'm considering turning on some equipment that hasn't seen a outlet in about 35 years. The 3 radio's I'm currently using were as the fore mentioned. Thay worked as thay did the last time I used them. If a capacitor or diode's gonna pop will it? Or is it true that bringing it up slowly during a period of a week or so using a variack will slowly bring old capacitors and anything else that can blow back to life? Do thay work or did I just get lucky with the 3 I fired up? Before I fired them up I did give them the once over. Anyone who knows old tube radios is that the once over gives no garranty that something doesn't smoke after many years idle. So do variaks really work? Will thay bring life to components bringing them up slowly. Or if it's gonna blow at full voltage its gonna blow wheather you bring it up slowly over a period of time? I don't own one. Should I buy one? I'd like to fire up a J.V. Valiant. Should I just use the money having a Tec. change out anything that can smoke? When I used it last I worked 100%. That was about 30 years ago. The same with the reciver.
 

I use a variac to bring up old tube equipment when I work on them.

Friend of mine just plugs it in and turns it on. He said if it is going to blow it will blow.


So it is your preference how you want to bring up your equipment.
 
Yes it is a variac as in variable AC voltage. I keep hearing people talk about bringing up the voltage over a period of days or even a week and that is ridiculous. I have a variac and have used it to power up 50 year old gear that was idle for nearly that long. The idea is to bring the voltage up slowly so that if something does blow the damage is limited by the lower voltage. typical power up time with a variac is in minutes and certainly not days.Old paper electrolytics may have to be reformed however the best thing is to replace them before applying power as they are likely dried out and bad anyway. If you want to do any work on old gear especially tube gear a variac is a great thing to have. Comes in handy when checking unknown transformer voltages too.
 
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VISUAL INSPECTION.

How can one tell which paper caps to change out given theres usually about a dozen or more. What's the signs of a poor paper cap? Concidering the caps are easy to replace should you just replace them all? So back to the variac. What you say is as you increase the voltage the items that will smoke will do so before topping out at the top voltage the item requires to operate at full capacity. Thus possibly damaging other components that do not need to be replaced. Or even worse blowing out an expensive transformer or the like. I was on the fence about purchasing one but after reading that last response I'm gonna buy one. Any suggetions on a fairly priced one that works well would be apreceated. I've seen many on eBay in advertised as excellent working condition for between $75 and $200. Should I go that route? I'm learning more and more. WWDX and it's members are friendly and knowledgable. As a matter of fact learning is just as much fun as qsl'ing. Thanks to all.
 
I restore old transistor CB radios and replace all of the electrolytic caps. Cost is about ~$8 for ~35 caps of different values. If it was my radio, I would replace them all with Nichicon or Panasonic caps. You may also have one of the 'canister' type of cap, that has 3 or 4 caps built in to it. I don't work on tube radios; but I have worked on tube guitar amps. Either you can gut that cap and put axial lead caps values inside of it - or even better to replace it with an original part if you can find one.

Forgot the name of the company that makes them, but if you call up a shop that repairs Fender guitar amps, I'll bet they can tell you where to find them and who makes them. Or they may even have one in stock and sell you one.
 
Last edited:
Stellasarat said:
How can one tell which paper caps to change out given theres usually about a dozen or more. What's the signs of a poor paper cap? Concidering the caps are easy to replace should you just replace them all? So back to the variac. What you say is as you increase the voltage the items that will smoke will do so before topping out at the top voltage the item requires to operate at full capacity. Thus possibly damaging other components that do not need to be replaced. Or even worse blowing out an expensive transformer or the like. I was on the fence about purchasing one but after reading that last response I'm gonna buy one. Any suggetions on a fairly priced one that works well would be apreceated. I've seen many on eBay in advertised as excellent working condition for between $75 and $200. Should I go that route? I'm learning more and more. WWDX and it's members are friendly and knowledgable. As a matter of fact learning is just as much fun as qsl'ing. Thanks to all.
Click to expand...


Ideally you monitor it with an ammeter so you can see if things start to draw too much current. Also with a quick turn on it will stress some of the old components and they may blow, especially the capacitors. As for the paper capacitors, usually they are bulging and the electrolytics are either bulging or leaking around the bottom seam. Best course of action is to simply replace all of them if in doubt.

As for buying one, they tend to be a bit pricey on Ebay, but then again everything can be. You may get a good deal but the usual caveats apply to Ebay. Try a local ham flea market. That is likely the best place. I picked up a really nice 5 amp variac for $35 at one.
 

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