Sovtek JMP-50 Transformer?

SwedishWings

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I was cleaning out some boxes and found this OPT.

3.2K primary impedance, probably 50W. I hooked it up in a 50W amp with 2xEL34 and it sounds ok, but i think it lacks a bit low-end compared to the original Marshall transformer.

What puzzle me is the marking "SOVTEK JMP50-2", that was written on the box and the transformer. Did such a thing ever exist? :)

1.jpg 2.jpg 3.jpg 4.jpg
 
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Pete Farrington

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What do the inked stamps on the side of the lamination stack say?
If they’re not cyrillic characters, perhaps that indicates that it’s not of Russian origin.
 

PelliX

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My guess would be that it was a replacement part for a JMP50 which also worked in some Sovtek model. It's very common to see stuff labeled like that in workshops. "This is a XXX which is for a YY123 and/or ZZ345". Plenty of that going on among my spares, at least... As @Pete Farrington pointed out, any stamped/original markings would be more decisive. The two markings on the top are just stamps to indicate it passed some QC tests.
 

XTRXTR

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Size, shape and wire colours look like Drake 784-139 to me.
Maybe pop the end bells off and see what it says inside?
Agreed same color codes as all my Drake 784-139, They weren't exclusive to Marshall.
 

Xenrelic

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That's a Marshall 50 watt replacement OT, it's basically a replica of the Drake 784-139, but built by Pacific Audio Transformers with a 3.2k - 3.6k Primary. They make the transformers that went into Ken Fisher's Trainwreck amps and Howard Dumble's Overdrive Special amps. Electro-Harmonix (formerly Sovtek/New Sensor) carries them in their catalog and I have a spare one direct from Pacific to confirm.
 

william vogel

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Those QC ink stamps do look like Pacific for sure and the endbell covers are American manufacture. If I saw the way the core winding looked with the endbell covers removed I could say for sure. Each manufacturer has their own unique outer wrap insulation and I’m familiar with them. It looks pacific though.
 

SwedishWings

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That's a Marshall 50 watt replacement OT, it's basically a replica of the Drake 784-139, but built by Pacific Audio Transformers with a 3.2k - 3.6k Primary. They make the transformers that went into Ken Fisher's Trainwreck amps and Howard Dumble's Overdrive Special amps. Electro-Harmonix (formerly Sovtek/New Sensor) carries them in their catalog and I have a spare one direct from Pacific to confirm.
Thanks for all answers. Life interrupted, but i finally got around to open it up and it was indeed a Pacific transformer. I measured around 3.2KΩ (plate to plate) primary indictance.

Screen Shot 2022-08-04 at 7.19.55 PM.jpg

Looking at the data sheet for Pacifics replacement for Drake 784-139 / Marshall TXOP-9002, it say 4.5KΩ:


@Xenrelic, you was spot on here. Do you know anything about the discrepancy in the data sheet?

Thanks and regards!
 

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