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Has anyone pulled the 12ax7's from the phono stage to reduce the current demand on the power transformer?
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In addition to items mentioned below, a portion of the transformer's heat is due to power dissipated in the primary winding itself. I've seen many vintage power transformers designed such that the inductance of the primary is simply insufficient to keep dissipated power at reasonable levels. That situation is aggravated by today's generally higher line voltages. I have Hammond filament transformers with 115/117VAC primaries that run so hot without a load, I can barely touch them.
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A friend of mine has one of those. The transformer does run hot. He rigged up a cheap DC fan salvaged from a computer to cool the transformer. Runs it on a 9V battery. It helps a lot.
As Mike said, disabling the phono stage will not make any difference. It's the power stage that is drawing all the current.
Could probably start at the primary which appears to be wound for 117V. 315V across the EL84's @ .050A (at the schematic's 117V) is almost 2 watts above the common datasheet dissipation of 12 for the plate and 2 for the screen, FWIW. My line voltage runs about 4% higher than 117.
You can do it but it won't help much because the two 12AX7s don't draw enough to make a huge difference. Let me guess.You want the power transformer to throw off less heat,right?
Nobody ever went broke underestimating the intelligence of the American public
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Edits: 03/20/15
The power transformer does get pretty hot. It seems that reducing filament and B+ current would be helpful.
You are only taking 600ma total filament current for the two 12AX7s. Those power transformers run inherently hot so don't be surprised if it doesn't cool the power transformer down after the two tubes are removed.
Nobody ever went broke underestimating the intelligence of the American public
H. L. Mencken
600ma is a fair amount of current. My B+ is running about 365v after recapping so a thermistor could lower the voltage some. Sound is great.
It is not the current, but watts that is a gage of power draw. 600ma x 6.3 volts = 3.78 watts. That is a small amount of power draw on a power transformer of guessing 150-200 watts (volt-amperes).
Has anyone reworked the phono stage to make it perform as well as the high level and output stages?
Replace the two .047 & .1uF with Russian K40Y-9 @ 200 volt. The 470pF & 3300pF can be replaced with silver mica or polystyrene capacitors. Use an audio grade 50uF on the first tube cathode such as Elna Silmic II.
Rolling 12AX7s will finish the upgrade. I noticed phono stages prefer crystal clear & neutral tubes. Brimar CV4004 or less expensive Westinghouse short narrow (not the wide ladder type) plate sound good in many vintage phono amps.
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