Another Westinghouse H840CK15

[trinescope]

Originally Posted by ohohyodafarted

Here are the DC resistances of the vertical convergence transformer. These readingx are taken directly from a known good trans that I removed from my CT100 and replaced with one of the replacement transformers that Folsom had for sale back in the day. The original has been sitting on my shelf for about 10 years because I am saving it in case of a failure in one of my 15" color sets.

The resistance of the primary is 1060 ohms.

The secondary is 20,300 ohms center tap to one end.
and 8700 ohms center tap to the other end
with an overall end to end resistance of 29,000 ohms.

That equates to about 27,645 feet (5.23 miles) of #40 wire on the secondary at 1049 ohms per 1000 feet of wire.

Hope this helps in your winding effort in the event you are unable to obtain a replacement.

Good Luck!

Thanks much for the information. I guess the Westinghouse and RCA transformers, although functionally equivalent, are actually constructed differently. Looking at the ad on the ETF website for the reproduction transformers, it says that 41 and 43AWG wires are used in the windings. My transformer had only 41AWG wire in both primary and secondary. The scan of the Sams folder for the Westinghouse shows secondary resistance readings of 3800 and 9200 ohms (although the scan is fuzzy in that area, so that's a best guess) whereas the RCA part as you measured is 8700 and 20300 ohms, respectively. The primary resistances are just about equal, however. My educated guess is the RCA part uses 43AWG wire on the secondary. 41AWG wire is about 1320 ohms/Kft and 43AWG is about 2140 ohms/Kft, quite a bit of difference. Using best guess turns per foot based on the location of the windings the primary is 2000 turns of 41AWG, and the secondary is 8700 + 17000 turns of 43AWG. For the Westinghouse part I get 2000 turns of 41AWG and 5750 + 12500 turns of 41AWG. Using the same insulation thickness the overall winding dimensions are roughly equal and just about fit in the E laminations.

The overall primary/secondary ratio looks to be different between these two if my assumptions and calculations are correct, but the tapped secondary ratios are nearly the same.

I don't know if I want to attempt this on my own or see if maybe Edcor or some other transformer company could produce this.