Today's Mystery Guest (RCA CTC-4)

[Phil Nelson]

The new part arrived (the extra can is from my TV).



The RCA part number is 100430 and the Meissner part number is 17-6014. I got this from Play Things of Past. I also checked with Moyer; they don't have the Meissner part but they do have a Miller 6025, which is equivalent according to their records.

I'm leaving tomorrow morning for another short trip, so I probably won't have time to play with this until next week.

Perhaps breadboarding this circuit is not a bad idea. In different schematics, the value of L42 is given as either 11 or 12 muh, and the value of C209 is given as 4, 4.7, or 6.8 pf. I believe I have all the needed parts on hand, except for a ready-made power supply. Maybe I can pull out the power/audio chassis from my Admiral 24C15 B/W set and tap that for B+ and filament voltage.

Phil Nelson

[old_coot88]

Before doing an external breadboarding, I would maybe try this first.. go ahead and mount the new can and hook up the primary (terms. B & E). Leave the secondaries completely unconnected to minimize loading.
Bring the scope probe close to either L42 or term. B to look for the osc signal.

It's amazing that part was still available.

[Phil Nelson]

Hmmm. I looked inside the can of the new transformer and discovered a resistor (looks like blue-gray-brown, 680 ohms) in parallel with each cap on the secondary coils:



The data sheet also shows these resistors:



Their "typical" circuit is different than the CTC-4, with a 6AN8 quadrature amp between the reference oscillator and the transformer. It looks like the circuit from the RCA CTC-2B; this schematic specifies the resistors as 680 ohms and the caps as 1500 pf:



The labeling of the secondary terminals is a little different and the resistances differ from the original. I measure 1.7 ohms across the primary (B-E) and .3 ohms across each secondary (F-D and A-C). The original measures 6.8 ohms on the primary and .2 ohms on each secondary.

The question is whether this is a good replacement for the CTC-4. I suppose I could just stick it in (noting the labeling differences on the secondaries) and try old_coot88's most recent suggestion . . . .

Phil Nelson