Stancor 25:1 [200 Ohms] RCA M-140552-6 Vintage Output Transformer OT potted Tested 35:1 1480:1 HUGE 2 lb Tube Amp Audio

One (1) fully 1.00 kHz AC tested and guaranteed vintage tube amp output transformer. AC testing using an oscilloscope allows us to find and reject transformers with noisy outputs, which a simple resistance or continuity test will not reveal. Made in USA in by Stancor for RCA. IEA date code 138639. Weighs 2 lbs 2 oz. Center-to-center bolt spacing is 60 mm, and height of casing is 76 mm. Quantity sometimes available - please enquire.

Using a 10V_pp, 1.00 kHz input to the primary coil, we have verified these connections for this vintage transformer:

The turns ratio (pri:sec) is 5:1, leading to an impedance ratio for the main secondary coil of 25:1. This winding of the transformer would provide a 200 ohm load resistance to the tube plate if you hook it to an 8 ohm speaker.

This model has multiple secondary taps. Additional impedance ratios of 35:1 (via the brown-green connections), and 1480:1 (via the yellow-black connections) are available as options.

Red/Blue striped is center tap on red-blue primary winding. Several other ratios available by mixing green, yellow, brown, and black taps on secondary.


Serial number O-1052.