Variac Recommendation Needed
 

A friend of mine and I are beginning restoration on a 1952 Magnavox B&W television (i.e. new caps, resistors, tubes etc.). I've been advised many times to slowly "bring up the voltage" with a variac. I've never used a variac. What would be the best one to buy for this purpose? Where should I buy it? How much should I expect to spend? What voltage increase schedule should I use? Thanks much!

I believe Antique Electrinic Supply has variacs. If you were to find a used one, that would be fine too. You could wire a light bulb in series with the line, starting with low wattage bulbs and working up to higher wattage ones.

Myself, I start the variac at 25 volts and increase by 5 volts every 15 minutes. You should hear something from the speaker at around 70 to 80 volts. At around 50 volts, I feel the electrolytic cans to see if they are overly warm (If the chassis is set on its side, heat transfer from the tubes). If the chassis is upright and a can gets overly warm, shut it off, the cap is bad. If you replace the lytics before applying power, do a slow start anyway. I got lucky with my Andrea. All but one lytic reformed.

If around 70 or 80 volts, you hear frying sounds from the power transformer, shut down.

During the soft start, disconnect the plate cap from the horiz out (or remove the tube). Running the hor out on reduced voltage will stress the fly. Once you are at full voltage, enable the hor out.

You might find a good used variac for around 20 bucks. I paid the best price for mine (free).

I should define "overly warm." I allow a little warmth from heat transfer from the tubes. If a cap is hot at low voltage, or you hear hissing, or it explodes, it's bad.

Hope this helps some.

Big Dave...thanks much. Years ago I tried the set at full power and heard some "sizzling" accompanied by a bit of smoke. I shut it down immediately...hopefully no serious damage was done...I can't see anything discolored or burnt. We'll see I guess, as we "get into it". I really appreciate the detailed advice. Best regards, Jim

I would probably just go ahead and replace all those caps, the electrolytics and the paper caps before you power it up again. Also check the 5U4 tube and make sure it was not damaged by a possible overload.

Will do...good advice, I'm sure. I'll post picture when it's up and running. Have a good week.