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

[ericj]

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

 

[HollowState]

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.

 

[ericj]

Ok, thanks for the input. I didn't realize it was for the pair

.:Sent by pneumatic tubes

 

[HollowState]

Well. on second thought the transformer could be rated for more because of the voltage doubler. That places a greater load on the transformer because of it's inefficiency.

 

[ericj]

I should probably just hook it up to a string of 3 or 4 60w bulbs and measure it

.:Sent by pneumatic tubes

 

[6L6]

That's a good idea... the HV tap is going to be lower than you think, maybe 200V or so... The B+ is being made by a voltage doubler.

 

[ericj]

Right, i hadn't spotted that 2nd cap and had parsed it as a full wave rectifier

.:Sent by pneumatic tubes

 

[danFrank]

The HV winding 150-160 volts.

 

[ericj]

The HV winding 150-160 volts.

With 3 60w bulbs in series across the hv secondary i show 181vac

.:Sent by pneumatic tubes