Old Heathkit O-11 Smokes.

Well, sort-of. One, use your nose and eyes and see if you can locate the stinky part (do not turn it on). Usually the electrolytics need either forming or replacement; prolly too late to try re-forming. It is possible the problem is in the transformer, which is special - it has a rather high voltage winding for the CRT, as i remember. That winding has a tendency to break down, which results in what you discovered (but ther may be other reasons for the smoke). If the transformer is definitely the stinky part, then it is a very good bet that HV winding is bad. If you took the transformer laminations off, thenyou may get a better look to find out if that winding is the outer-most one. If so, then one could replace it, using better materials. Count the turns per layer for the first 2 or 3 layers, and the number of layers for the total turns. You can use thin mylar tape for insulation in place wher paper was used when you re-wind. When the transformer in my O-1 when bad, i ordered a replacement transformer from Heath (the O-1 was a kit still being sold then). Be advised that this project would be useful only for re-habilitation for working antique sales or other profitable purposes. The O-1, while better than a number of the other inexpensive kits and scopes at that time, you can get far better (used) scopes now for a cost less than the time involved for restoration.

Reforming, that's when you use a variac and warm up the unit at a lower voltage for a while?

CV

The large Astron can cap seems to have leaked. It's rated at 40mfd,

Aye-Yup! And crank up slowly.

In article , snipped-for-privacy@yahoo.com mentioned...

Some of the caps are over a thousand volts. They're filtering for the tube's high voltage.

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I'd stick with paper, if the proper kind is used it would be better for a transformer that's in hot tube equipment.

Really. And they won't be using toobs. One thing that could be donw is if the high V winding is the problem and the rest of the transformer works okay, then use a tripler or more for the high V.

The problem is, that there are shorted turns in the transformer - which will mwke it overheat. So one should *not* use it!

I have seen a lot of these old Heath, Eico and RCA tube scopes with a separate filament transformer added because the insulation was breaking down in the original transformer, and people used them daily, for years.

The transformer in the Heath supplys everything, and if the CRT HV winding goes, then it needs replacement or re-winding.

Robert, i have disconnected the separate 6.3 volt winding from the CRT and replaced it with a separate transformer and had it work quite a few times. I've done it to Heath, Eico, RCA, and other brands. It depends on the problems in the original transformer, but its a lot better than trashing a scope if you don't have another to replace it with.

Well, like i said, there are a number of windings on the power transformer, and all of the failures i saw and/or experienced were related to the CRT high voltage winding. If there was arcing in any of the HV windings, or arc-over to any other winding, it is not safe to use the transformer without complete repair/replacement. Now, if (somehow) a filament winding fails open, *then* your strategy is acceptable.