Output transformer max voltage?

[glebert]

Hopefully not too dumb a question, but I have an Eden E300T with bad OT. There is no replacement part available from Eden. Something like an SVT or Hammond OT is over $300. I am wondering if I can instead set this up as a lower powered head with an OT salvaged from a lower powered amp. I'm thinking about using one pair of 6550s or maybe a quad of 6L6GCs. I'm wondering though if the OT needs to be specifically designed for the high plate voltages that this amp has (640V) as opposed to many 6L6 type amps running plate voltages closer to 500V.

Thanks,
Greg

[g1]

No, the OT doesn't care.
But your B+ levels will rise with the reduced loading of the supply, so you may have to deal with that.
Can you post a schematic? I'm not sure 6L6's would like that kind of plate voltage in a standard arrangement.

[glebert]

I'm not sure 6L6's would like that kind of plate voltage in a standard arrangement.

From what I have read the JJ 6L6GCs are good for these high voltages. I think Music Man amps run the plates up at least this high.

Here is the schematic.eden WTB300V sch_1.zip E300T and WTB300V are almost exactly the same.

[g1]

Others that get away with it do not use what I would call 'standard arrangement'. For example, the musicman is running the screens at about half of what is on the plates.
In this case you only have a choke and a 560R between plate and screen nodes. Do you know what the actual DC voltage is at the screens?

[vintagekiki]

Hopefully not too dumb a question, but I have an Eden E300T with bad OT. There is no replacement part available from Eden. Something like an SVT or Hammond OT is over $300. I am wondering if I can instead set this up as a lower powered head with an OT salvaged from a lower powered amp. I'm thinking about using one pair of 6550s or maybe a quad of 6L6GCs. I'm wondering though if the OT needs to be specifically designed for the high plate voltages that this amp has (640V) as opposed to many 6L6 type amps running plate voltages closer to 500V.

Thanks,
Greg

For the output transformer, it is not so important the plate voltage data, how important is the data for how much power is provided, how much is the allowed primary current and how much is the primary impedance (Raa).

Transformer protection against high plate voltage, provided with double insulated wire which is wound, interlayer insulation between rows of primary windings and immersed windings in varnish

How much power the transformer can withstand, depends on the thickness of the primary wire, respectively how much current it can withstand.

When replacing the output transformer, it is very important to know how much is predicted the output tubes (duet, quartet, sextet), how much current it can withstand (since thickness of the primary wire) and how much is the primary impedance (Raa).


Instead of looking to replace the output transformer try in a locale where you, find a technician and rewind your original transformer (one-on-one)

[glebert]

Others that get away with it do not use what I would call 'standard arrangement'. For example, the musicman is running the screens at about half of what is on the plates.
In this case you only have a choke and a 560R between plate and screen nodes. Do you know what the actual DC voltage is at the screens?

Excellent point, I will keep that in mind. My first option would probably be a pair of 6550/KT88s.

[Mick Bailey]

With the reduced PT load with just a pair of tubes and the previously mentioned increase in B+ my choice for a pair of tubes would be KT88, which has better figures than the 6550

[J M Fahey]

I have an Eden E300T with bad OT. There is no replacement part available from Eden. Something like an SVT or Hammond OT is over $300. I am wondering if I can instead set this up as a lower powered head with an OT salvaged from a lower powered amp.

Shrt answer: no.
Like sage Enzo often says, "the amplifier is that thingie between the power supply and the speaker"
The amplifier basically "throttles" voltage and current from supply to speaker.
You still have a 300W RMS capable (so probably 600W DC capable) power supply, and you are trying to throttle it with a woefully underrated tube complement and OT: a recipe for disaster.

Either pay through the nose for the proper OT, or get a salvaged one (if available) or have that one rewound.
All of vintagekiki warnings apply.

I'm thinking about using one pair of 6550s

Not enough dissipation nor current handling.

or maybe a quad of 6L6GCs.

Even worse.

Plan B:
Absolute worst case, use 4 x 6L6 + a Bassman class OT + a Bassman class PT which is the proper "everything fits" way and turn that (current) boat anchor into a usable amplifier.
But you´ll need to remake the Power Supply

I'm wondering though if the OT needs to be specifically designed for the high plate voltages that this amp has (640V) as opposed to many 6L6 type amps running plate voltages closer to 500V.

It´s not so much a problem of "voltage" (although that is also an important factor) but of raw power handling.

If you want to save by using cheap or cannibalized parts, good, build a full Bassman or Sunn or V4B supply and amplifier.

But rewinding looks a sensible option.
No clue on cost, can you search and post a couple price quotations?

[vintagekiki]

But rewinding looks a sensible option.

For rewinding technicians charge 25 to 40% of the cost a new transformer.
The advantage of rewinding is that the original core with the original windings.
Simply Eden E300T is in good condition, completely refurbished