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 RCA WR-49B open AF oscillator transformer
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 Return to top of page · Post #: 1 · Written at 11:12:40 AM on 8 June 2020.
BurntOutElectronics's Gravatar
 Location: Alexandra, VIC
 Member since 2 October 2019
 Member #: 2392
 Postcount: 213

I was given this nice old signal generator a while back and repaired it but upon testing it's functionality
It turned out the 1:1 transformer for the 6C4 is open on one side
The manual doesn't give a impedance value but I did measure the good side and it reads 246 DC ohms.
I don't know what I could replace it with.

Here's the manual


If anyone has a old transformer that would work I'd be willing to pay or even if someone has a wr-49b that they are willing to sell I'm also interested.

 Return to top of page · Post #: 2 · Written at 11:27:05 AM on 8 June 2020.
Ian Robertson's Gravatar
 Location: Belrose, NSW
 Member since 31 December 2015
 Member #: 1844
 Postcount: 1981

This should work and it's in stock too:


This would also work:


I'm sure these are both physically smaller but don't let that worry you.

If it doesn't oscillate, reverse the connections on one side.

 Return to top of page · Post #: 3 · Written at 11:45:28 AM on 8 June 2020.
Trobbins's avatar
 Location: Melbourne, VIC
 Member since 11 July 2012
 Member #: 1179
 Postcount: 44

It seems like it would be a small output transformer of no more than about 30dBm (1W), and the primary operates at about 3.5mADC, and with a 135VDC B+ and 2.5V bias, the 6C4 datasheet indicates any primary impedance loading of circa 15k to 30k would seem ok, with a 10k to 50k secondary (given the 33k grid leak and 33k signal feed). Trimax seem to have a never ending listing of signal transformers that may fit.

PS. And just seeing Ian's suggestions - they seem to fit.

 Return to top of page · Post #: 4 · Written at 12:51:38 PM on 8 June 2020.
BurntOutElectronics's Gravatar
 Location: Alexandra, VIC
 Member since 2 October 2019
 Member #: 2392
 Postcount: 213

Thanks guys

I'll probably go with the altronics transformer and we'll see how I go.
It's a nice little signal generator and I'd imagine this 240v version would be fairly rare.


RCA Signal Generator
RCA Signal Generator
RCA Signal Generator

 Return to top of page · Post #: 5 · Written at 4:48:31 PM on 8 June 2020.
Marcc's avatar
 Location: Wangaratta, VIC
 Member since 21 February 2009
 Member #: 438
 Postcount: 4460

It should not be an issue to use a 240V primary transformer. I always have issues with that line cap configurating on a non grounded chassis.

 Return to top of page · Post #: 6 · Written at 10:10:37 PM on 10 June 2020.
Brad's avatar
 Location: Greenwich, NSW
 Member since 15 November 2005
 Member #: 1
 Postcount: 6532

Photos uploaded to Post 4.

A valve a day keeps the transistor away...

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