Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: mk_716 on April 05, 2022, 08:55:18 pm
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Hello all,
I've got a donor V22 that I'd like to use the iron from this amp (the amp is board is beyond repair).
I'm especially interested in the heater current, looks like V1, V2 and V3 heaters are all on a 15V DC and just the power tubes are using the 6.3V.
Makes me suspicious there isn't much current there.
Does anyone know? I've been searching and I can't find it on the webs.
Thanks in advance,
mike
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> looks like V1, V2 and V3 heaters are all on a 15V DC
Now, they are clearly on +/-18V.
Why can't you do it the same way? Do you need more than three small bottles?
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Hello all,
... heater current, looks like V1, V2 and V3 heaters are all on a 15V DC and just the power tubes are using the 6.3V.
Makes me suspicious there isn't much current there.
What PRR said - its from the +/-25VDC supply dropping to +/- 18VDC via the 47Rs. Total current draw is 150mA for this part of the circuit
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Hey guys, yes 18v sorry.
What I'd like to do is sluckey's AC-15, lots more bottles. I want to think using a similar method I could squeeze out enough, but I'm just not sure. (Just under 4 for that) feels like I'm pushing my luck.
Sluckey's Dual-Lite is my plan b which is probably a more sensible choice with what I've got...
Mike
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Might be less stressful to use a more appropriate PT.
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Remember that voltage in series adds up, but the same current 'flows' through all components in series. 50VDC (+/- 25VDC) is borderline for 4 x 12AX7 filaments in series @ 150mA (4 x 12.6 = 50.4) as you wouldn't have room for any limiting resistors to deal with startup surge. (Resistance is lower at colder temperature, so you'll get a spike in voltage at startup until the heaters warm up, which is not good for a maxed out +/- VDC power supply without any limiting resistance in series.)
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Thanks guys,
m.