RCA Victor Model 66x1

3/31/2009 12:24:57 PMVinny

What is the right replacement output transformer.

3/31/2009 2:01:58 PMLewis L

:What is the right replacement output transformer.

Hoo, boy!! That tapped primary. The 35L6 is a 2000 Ohm tube, so a 2k to voice coil will work if you just connect the B+ to the 1.2k resistor, should be jes' fine. If you want to be strictly original, I don't know where you would find an exact replacement transformer.

3/31/2009 4:13:43 PMThomas Dermody

The original transformer is a hum bucking transformer. If it is shot and you cannot find a replacement, you can also reduce hum somewhat with negative feedback, which will also improve the audio quality.

If you cannot replace the transformer with a duplicate, and you find the hum objectionable, let me know if you want the negative feedback circuit. It is simple, and works well. There is another version that others have suggested on here that is to simply tie the low end of the volume control to the chassis through the output transformer secondary (connect transformer so as to provide negative and not positive feedback). However, I found that even with negative feedback there still is some objectionable high frequency oscillation. Try it out and if you don't like it, I can give you my circuit: a couple of resistors and capacitors.

3/31/2009 10:05:34 PMEdd

I wonder what is your analysis of failure mode on that unit, an open primary winding ?

If the primary is open, have you vewwy carefully, surgically peeled back the thin fishpaper covering and used a magnifier, hi-intensity light, surgical tweezers and ohmmeter to see if you lucked out, with the break being externally-accessible and can be micro-repaired on the re connection to its main lead wires.

It looks like in the referencing in the RCA service info, that the one sub that is suggested is having to be mechanically remounted AND the real point is that it is a conventional transformer with a single winding and no hum bucking tap.

They just want you to then compensate by heavier DC filtering.

The only other source that I see is the site I give below, to then see if they still have those in stock. Both units given have tapped primary windings for the RCA’s hum bucking aspect.

The first ones impedance match will be giving a skosh more treble response, while the second one will be giving a skosk bit more bass .

If you go for the usual sourcing of a Hammond you would be paying QUITE a bit ‘mo munny, and STILL no hum bucking tap like the units below are offering .

---The Site---clickee-clickee-pleeze

---The Transformer List---clickee-clickee-pleeze

1012-072 OUTPUT THOROTEST TA20T SP (1.7K z0 TO 3.2 VC, W/HUM TAP, 3-5 WATTS, FIG 3, NEW.. 1 2 3/8 1 3/8 1 1/2 $7.50

4565-116 OUTPUT THORDRSN T-24S89 SP (3K Z W/3% & 6% HUM TAPS) TO 4 V.C., 3-5 WATTS, FIG 3,N 1 2 3/8 1 3/8 1 1/4 $8.75

73's de Edd

4/1/2009 1:31:42 PMVinny

:What is the right replacement output transformer.