RCA 630TS Resistance Measurement

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If it works fine disconnected, it's probably ok. I'll bet the problem is hidden in the chassis in some non-obvious place.

For the trans to be bad, as far as I know, it would have to fail in one of three ways:

(1) One of the windings goes open. This would be obvious because one winding wouldn't work.

(2) One of the windings has a shorted turn. This causes a whole bunch of energy to be unloaded into that one shorted turn. If you disconnect everything like you did, and apply power to the primary, it should burn up just as bad with no load on it as it did loaded. A multimeter wont test for this, because one shorted turn wont change the resistance of a winding much.

(3) One of the windings has a short to ground. All of them should be insulated from the frame.

Of the above options, number three is just about the only one left. That, or the transformer is not bad.

If you have a dim bulb tester lash-up, you could check it with that. With everything laying on an insulating surface, one side of the power line would go *through* the light bulb to the transformer frame. The other side of the power line goes to *one* wire from any winding. When energized, the bulb should not light. Try with one wire from each winding. Obviously, don't touch anything while it's energized.

If the bulb never lights, it passes the test. If it fails the test, you still might be able to take the end bells off and fix it.

If your rectifier socket was shorted from a filament pin to ground, things would only heat up with the rectifier in the socket, because only then would the filament pins be hot with B+

When B+ comes up, the rectifier filament and winding floats at B+. If the winding is shorted to the transformer frame, that is a short from b+ to ground.

What comes next? The 80uf capacitor? Could it be backwards? What comes after that? A choke or a speaker field? Could it be shorted to ground?

I don't have a schematic for this set in front of me, but usually one of the filament windings (for the other tubes) is grounded on one side. If the other one gets grounded by a defective tube socket or lamp socket or something, you would get smoke.

If it passes the funky dim-bulb leakage test, and you're gonna put it back in, I would hook it up a little at a time. First just the HV winding, and not much will happen. Then add the rectifier filament winding. This will bring up B+, and things will probably go to hell. If they do, see if disconnecting the lead to the 80uf and B+ bus fixes it. If it's ok, proceed to a filament winding (which will put some load on B+), and so on.

By the way, if the excessive current draw is further down the B+ chain, it should be easy to find. RCA usually gives the voltages of several B+ taps. Find the first one that is way low and look there.

Good luck,

John