Help ID these little PP output xfrmrs?

[duganj]

Yet another unknown surplus store score:



I've tried the usual path of the Google with no luck.

Primaries are 2 red and one yellow (CT) I assume.

Secondaries are Black, Blue, Green, Yellow for 0,4,8,16 Ohm, also assumed.

Numbers are 1400 MG on both, then 839006 on one, 839007 on the other.

No markings on the other bell.

They are fairly small, that's a 6JN6 for reference.

Does Sams have a reference for transformers only? Or do you have to know the equipment that it came out of?

If I can't find any info on them, I figure I'll just back out the turns ratio and put them into service in a 10-15 watt or less amp to play it relatively safe.

Any input appreciated, thanks, John.

[Mr. Triatic]

dont recognize them, but due to the size i guess they could have been used with 6BM8, depending of the primary Z of course..

[leadbelly]

Originally Posted by duganj

If I can't find any info on them, I figure I'll just back out the turns ratio and put them into service in a 10-15 watt or less amp to play it relatively safe.

If you can't verify that they are voltage rated for tubes, then building a tube amp with them is hardly "safe" by any stretch. Did you get any information when you bought them that they were tube OPT's and not for a vintage SS amp?

[Eli Duttman]

I'll venture a guess that 839006 and 839007 are serial numbers.

The kind of trafos found in early SS gear were much smaller. We're talking mW. power that my dad's RCA radio, with 2N109 "finals", yielded.

The 6BM8 suggestion previously made seems valid to me. Think about Fisher/Scott/Dyna style circuitry, with a voltage amplifier DC coupled to a "concertina" phase splitter. St. Petersburg made 6BM8s are decent. You'll need 2 pairs. The power pentode sections of each pair should be well matched. Don't forget to regulate g2 B+.

[rotaspec]

They look similar in size to a pair I picked up a while ago. They came from a console with 2x ECL86 (6GW8) in PP on each channel. Looking at them and the specs for the ECL86 in PP configuration, they should be good for an honest 10W each.
Unfortunately one of mine had been overheated

Gary

[Eli Duttman]

They look similar in size to a pair I picked up a while ago. They came from a console with 2x ECL86 (6GW8) in PP on each channel.

The power pentode in the 6GW8/ECL86 is somewhat more "muscular" than its counterpart in the 6BM8/ECL82. A power O/P of 10 W. from a PP pair of 6BM8s strikes me as being overly ambitious. TDSL shows 3.5 W. from a SE 6BM8, at a high level of distortion. 8 clean WPC from a PP pair of 6BM8s seems reasonable to me. AAMOF, the little ASL Wave AV8 monoblocks available commercially not that long ago were rated for 8 W. each and they used 6BM8s.

[duganj]

Agreed that they are most likely not SS outputs. From what I've seen, on the SS output xfmrs the primary impedances are significantly lower than common tube outputs. Say hundreds of Ohms vs thousands in tube gear. So that should be another clue.

I'll try and back out the turns ratio at work tomorrow where I have better gear to do it.

One potential application that crossed my mind was a Self Inverting PP output stage a la Mr. Leibowitz: Compact Hi-Fi Power Amplifier by Melvin Leibowitz - Electronics World, June 1961

It's something I've always been curious about. Perhaps one of the more modern variants with a CCS on the cathodes. Although 15W of PP EL84 or some similar variant may be pushing the upper limit of these little guys. EDIT: 15W is a bit high, the article calls it a 6W amp.

[DigitalJunkie]

Might I ask where you picked them up from? I sort of suspect R5D3,but I haven't been there in a while,and am curious to know if Bob is still in business.

[duganj]

R5D3 indeed, certainly still in business and worth a trip depending on what you are looking for.

[DigitalJunkie]

Cool,glad to hear that he's still open. I'll have to stop by sometime soon. Thanks!