RCA 630TS Resistance Measurement

[John Folsom]

Jonathan,

The resistance from B+ to ground should be approximately the sum of the bleeder resistors between B+ and ground, which is about 8k ohms. Likewise, from B- to ground should be about 500 ohms, and from B+ to B- about 8.5K. 10 ohms is WAY to small!

First, remove the 5U4's, and measure from the filament pins to ground (or -100V, it does not much matter, you are looking for thousands of ohms verses 10 ohms). If you still get 10 ohms, you need to start unhooking wires in the B+ B- distribution to fault isolate the short. An obvious place to start would be to unhook the low side of the field coil, and measure from the 5U4 filaments to ground. If you still have 10 ohms, the fault is either in the field coil, the electrolytic(s), or the secondary circuit of the transformer. And if not, the fault is downstream of the field coil. Continue to unhook portions of the B+ and B- circuitry to isolate the fault. Just follow you nose, and you will find the fault.