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I accidentally a set of transformers, x-100. Now what...

loudnoises

loudnoises

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So it seems I was sleep shopping, or who knows. I've apparently purchased a transformer set for a fisher x-100. Good price, someone was parting one out and I food it early.

I don't own an x-100. Nor do I have a chassis.

I suppose they'd be just fine for any number of clone builds?

Or might these work in my x202! Oh I may have to test that one...
 
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X100 is EL84 right? Should be suitable for any EL84 or 6V6 circuit you want to build around them. Are these the ones that people are semi-regularly looking for replacements for because the primary has gone open? If so I'd go for a more conservative build that doesn't push them for voltage or current just to reduce the chances of failure.
 
gadget73 said:
X100 is EL84 right? Should be suitable for any EL84 or 6V6 circuit you want to build around them. Are these the ones that people are semi-regularly looking for replacements for because the primary has gone open? If so I'd go for a more conservative build that doesn't push them for voltage or current just to reduce the chances of failure.
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I think so. if they're the actual x-100 it was a 7189 label. Listed as testing good, I'll have to read up once they're in hand and i can put a meter on them.

The way my world works i think I could use maybe one low power tube amp to run some horns. And they'd "replace" a set of 30a that are arguably not much different and still giving me trouble...
 
There's a fairly decent number of ways to use those. Anything from a conservative Fisher clone, to an off the wall compactron or TV line output tube build. Or one of the RCA tube manual designs.

Look forward to seeing what you come up with!
 
Aaaand the answer is...

They're from an X100-3. Found one schematic so far but it's not the Sam's listing the specs. They're in pretty good shape and the opts have nice long leads. Wires are not cloth. And in nice shape.

The bench is in a state of disarray so it'll be the shelf for these for now.

Damn that shelf is getting full...
 
I build a clone of the 500c power amp using original transformers. You could do similarly with the X100-3 transformers. The Fisher power amp sections aren’t too complicated and in a scratch build it is fairly easy to include individual bias and EFB circuits.
 
I'd modify it slightly to be more conventional cathode bias if you do this, or just negative grid bias rather than the setup that runs the tube heaters off the cathode circuit and feeds positive voltage in to the grid. Ends up with 30v less on the plate, but the actual voltage across the tube is the same. That will also let it run at lower current which the output tubes (and the transformers) will appreciate.

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is the stock schematic. Basically what i mean is eliminate that whole chain of tubes in the middle and sub it with EFB or resistors to develop ~12v to bias it properly. Grids would go to ground. I can see a good argument for running the screens off an EFB regulator too as they will probably have a decent amount of sag from idle to full output. Plate voltage would be 360 to ground instead of 390, screens 310v instead of 340. Voltage across the tube remains the same. Voltage supply to the 12ax7 would remain at 330V. Don't need any of the other voltages since they run the preamp bits.

Input grid to ground resistor would end up at 220K (or 270K, not fussy) to keep it all basically as-designed but as a straightforward power amp.
 
gadget73 said:
X100 is EL84 right? Should be suitable for any EL84 or 6V6 circuit you want to build around them. Are these the ones that people are semi-regularly looking for replacements for because the primary has gone open? If so I'd go for a more conservative build that doesn't push them for voltage or current just to reduce the chances of failure.
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If I had to choose I would build an amp around EL84's over 6V6's. I have three different EL84 ams and like how all three sound over the 6V6 amps I've owned.
 
EL84 has about 3 times the gm of 6V6 so less drive voltage required and maybe more sensitive to small signal changes. OTOH, with an appropriate driver the 6V6 can sound great too. I have both PP and SE with both and like them all.
 
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