Hi
I would greatly appreciate some help with this amp. The High Voltage toroid transformer has blown. The original transformer is from Toriod International Ltd with P/N TI-65765B. I could not source the exact transformer. I would like to know what are the secondary voltages so that I can source locally. There are three wires on the secondary. Red, Black and Orange. I guess the black is the center tap. Pls assist.
Thanks
I would greatly appreciate some help with this amp. The High Voltage toroid transformer has blown. The original transformer is from Toriod International Ltd with P/N TI-65765B. I could not source the exact transformer. I would like to know what are the secondary voltages so that I can source locally. There are three wires on the secondary. Red, Black and Orange. I guess the black is the center tap. Pls assist.
Thanks
Have you talked to Marshall direct. They should know what the voltages are if anyone does. They may be able to help with a spare transformer. This guy might be able to help you with the transformer voltages. Servicing a Marshall VBA 400 Amplifier Head
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It is 650Vp 375Vg2, as eight 6550/KT88 for 400 Watts. So about 1,200mA DC (perhaps 460V CT 2A AC, a 900+VA part).
This is not any sort of standard part. Not even found in other super-amps like SVT or Fender 300. I don't immediately see a hit at Antek. I'd be pricing for a flock of 115V 250VA isolation transformers (4*115V= 460V with tap for 230V).
This is not any sort of standard part. Not even found in other super-amps like SVT or Fender 300. I don't immediately see a hit at Antek. I'd be pricing for a flock of 115V 250VA isolation transformers (4*115V= 460V with tap for 230V).
If unavailable write those great Polish transformer makers for a quote.
Don´t remember the brand but they are known and respected and should be easy to find.
Wouldn´t be surprised at them being the OEM makers for the Marshall one, go figure.
And in any case, PRR's deductions about voltages are quite reasonble; absolute worst case use "whatever Ampeg does with its own 6550 powered amps".
"800V" is datasheet maximum, no sane Manufacturer would routinely use such values for safety reasons.
Toroid diameter, thickness, weight (all of which you can measure) will help custom winder clone it better.
In any case, a beast of a transformer.
You are lucky at it supplying HV onl; a Korean amp (are you listening Hartke?
)would use a transformer with a myriad low voltge windings, which to boot would be regulated so no direct math to find AC voltages, load currents would be unknown, a nightmare.
Don´t remember the brand but they are known and respected and should be easy to find.
Wouldn´t be surprised at them being the OEM makers for the Marshall one, go figure.
And in any case, PRR's deductions about voltages are quite reasonble; absolute worst case use "whatever Ampeg does with its own 6550 powered amps".
"800V" is datasheet maximum, no sane Manufacturer would routinely use such values for safety reasons.
Toroid diameter, thickness, weight (all of which you can measure) will help custom winder clone it better.
In any case, a beast of a transformer.
You are lucky at it supplying HV onl; a Korean amp (are you listening Hartke?
)would use a transformer with a myriad low voltge windings, which to boot would be regulated so no direct math to find AC voltages, load currents would be unknown, a nightmare.
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6550 Design Maximum rating is 660V.
EL34 has a 800V rating; few try it.
KT88 has a 800V "maximum" rating.
But when you already have an output transformer, the supply voltage "must" be real close to what that OT and tube-set was designed for.
If unavailable write those great Polish transformer makers for a quote.
Don´t remember the brand but they are known and respected and should be easy to find.
Wouldn´t be surprised at them being the OEM makers for the Marshall one, go figure.
And in any case, PRR's deductions about voltages are quite reasonble; absolute worst case use "whatever Ampeg does with its own 6550 powered amps".
"800V" is datasheet maximum, no sane Manufacturer would routinely use such values for safety reasons.
Toroid diameter, thickness, weight (all of which you can measure) will help custom winder clone it better.
In any case, a beast of a transformer.
You are lucky at it supplying HV onl; a Korean amp (are you listening Hartke?
Noted. Thanks