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 Wanted - Info on transistor radio transformer Rola JTR27
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 Return to top of page · Post #: 1 · Written at 8:35:53 PM on 7 August 2018.
Ross Herbert's avatar
 Location: Carine, WA
 Member since 6 August 2018
 Member #: 2276
 Postcount: 6

Just wondering if anybody may have come across this transformer or hopefully have a catalogue page with the data for it.

I have searched the Rola catalogue on KC's website but this refers only to valve radio and amplifier transformers.


This tiny transformer would probably be from the 60's and I am fairly sure it is a push-pull output transformer going by the winding resistances.

These are the details;
Centre-tapped winding (transistor push-pull side) measuring 15 Ohms per side. Wire colours Blue - Red (ct) - Brown
Speaker winding measures 0.95 Ohms. Wire colours Green - Black

My guess is that the transformer is for a speaker impedance of 8 Ohms and the primary impedance would be around 350 - 400 Ohms . 400Hz. Power rating would be no more than 200mW.

Regards to all

 Return to top of page · Post #: 2 · Written at 9:27:06 PM on 7 August 2018.
Johnny's avatar
 Location: Hobart, TAS
 Member since 31 July 2016
 Member #: 1959
 Postcount: 337

Sounds like a Jaycar MM2530 1K Center taped to 8 ohms, 300mW would probably do the trick.
Or if you use a 15 ohm speaker it would become an approx 2K CT/15. etc.

 Return to top of page · Post #: 3 · Written at 1:28:11 PM on 8 August 2018.
Ross Herbert's avatar
 Location: Carine, WA
 Member since 6 August 2018
 Member #: 2276
 Postcount: 6

Thanks for the tip Johnny - will check out the Jaycar transformer for comparison.

Actually, I wanted a real copy of a pamphlet or data sheet for the Rola JTR27 mainly because it is brand new and still in its original carton. Sort of a collectable item perhaps...

 Return to top of page · Post #: 4 · Written at 4:41:13 PM on 8 August 2018.
MonochromeTV's avatar
 Location: Melbourne, VIC
 Member since 20 September 2011
 Member #: 1009
 Postcount: 1056

I just had a look at a Rola/Plessey Loudspeaker Data guide.

All it says for the JTR27 is that is a output transformer, 450 CT/15. There are no other details, pictures or dimensions.

 Return to top of page · Post #: 5 · Written at 8:57:12 PM on 10 August 2018.
Ross Herbert's avatar
 Location: Carine, WA
 Member since 6 August 2018
 Member #: 2276
 Postcount: 6

Hi MonochromeTV,

The 15 Ohm secondary impedance is good to know.

I managed to borrow an LCR meter and discovered the primary inductance . 1Khz was 65mH per side which means the 450 Ohms would be about right.

Would you be able to make the Plessey-Rola data catalogue available?

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