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Sanity check my unlabeled transformer guesstimates? Fisher X-200 power trafo

ericj

Member
2008-12-08 10:24 pm
I thought I'd try and characterize a large power transformer i bought 10 years ago on spec.

On a whim i put the only number on it into google and it pulled up the Fisher X-200 repair manual.

T908-115 if anyone cares. I've attached the relevant portion of the schematic.

Looks like 300v, 6.3v, and maybe 22vct?

It powers four 7591 and a half a dozen 12ax7, so the 6.3v tap must be at least 3 amps and change. 12ax7 have DC heaters in 24v strings, coming off the bias tap.

7591 datasheet suggests that the plate current at idle in PP class AB1 would be 80ma or so, peaking well over 100ma, so the 300v tap must be 350ma or greater, right?

You'll find the entire manual at this address: http://www.fisherconsoles.com/non console manuals/fisher x200 beg 40001 sm.pdf
 

Attachments

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7591 datasheet suggests that the plate current at idle in PP class AB1 would be 80ma or so, peaking well over 100ma, so the 300v tap must be 350ma or greater, right?
I think 350ma is too high. 80ma quiescent draw is for two tubes. Double that for 160ma plus perhaps another 40ma for the six 12AX7s. (200ma) So my guess would be 275 or maybe 300ma max. Extra current for musical peaks is intermittent.