Using a Variac for testing Transmitter?

[K3STX]

I just picked up a nice Heathkit DX-60B with HG-10B VFO today. EVERYTHING is original, even caps. I want to " it up" slowly on a variac to keep an eye on it, reform electrolytics, etc.. but don't know how to do it. With transmitter bad filter caps produce obvious hum, but how do I know how the transmitter is holding up as I crank up the voltage.

How slow do you go? Any advice would be appreciated, I used to use a dim-bulb tester for everything before I got this new-fangled variac (from a dumpster at work, it works great).

paul

[N6LTU]

I used a dim bulb tester awhile back when I fired up my old TS-820S. It had been sitting unused for about 20years. I only had to use about three different types of bulbs to take it from low voltage to full. Didn't have a problem and she's still working, although she about to be replaced by a FT-450AT. :D

[AG3Y]

I just occasionally feel the cases of the caps to see if they are hot. Of course, if they are metal cases, and the caps are wired in series, you don't want to do that !

You might want to feel the case of the transformer itself, as it should be at ground potential and should be reasonably cool to the touch if everything is working OK. How warm is "reasonably cool", well you DON'T want to burn your fingers, or smell any varnish when doing the tests !

[K3STX]

Ahh, the old touch and smell test, a time-proven classic!! Thanks guys.

I am a recent convert from the "automatic recap" school. Can't wait to get this guy on the air. Starting her up for an hour at 40 volts, then another hour at 70 volts, then up to 100 volts certainly can't hurt. Looking forward to getting it on the air.

paul

[WA0JDL]

What wattage of bulbs did you use, and in what steps where you able to lower the voltage?
Thanks, Larry, WA0JDL

[KF5FEI]

I don't think I'd want to be poking around in the chassis with my fingers -- one of those infra-red thermometer guns might be a better choice. They are cheap and work pretty well for troubleshooting.

And an FYI for those unfamiliar with variacs -- the standard ones do not provide isolation from the line input. Most repair shops use an isolation transformer before the variac to protect the employee and to prevent damage to o-scopes, etc... when the chassis ground is above the power ground.

[K8ERV]

[QUOTE=KF5FEI;1964364]I don't think I'd want to be poking around in the chassis with my fingers --QUOTE]

I agree, I always use someone else's fingers. Saves a lotta pain that way.

TOM K8ERV Montrose Colo

[N6LTU]

What wattage of bulbs did you use, and in what steps where you able to lower the voltage?
Thanks, Larry, WA0JDL

I as I remember I used bulbs in this order: 40w - 60w -75w- 100w bulb.

N6LTU

[K9STH]

Even if you reform the electrolytic capacitors there is a VERY good chance that they will go "bad" in a fairly short period. You will either pay now or pay even more later. I suggest that you go ahead and replace the electrolytics. Frankly, I never use a variac when working on "boat anchors".

Glen, K9STH

[WA0JDL]

Thanks for the info, I have an old CW rig, that appears to be almost unused, but hate to fire it up full power. I may try your method.
Thanks, Larry, WA0JDL

[AG3Y]

" a time-proven classic!! "

Thanks, Paul, that's me, a " a time-proven classic!! :eek: :rolleyes: ;) :D