Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: DummyLoad on December 08, 2014, 12:54:40 am
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any of the four examples (A-D) in the attached examples won't work and why? assume all examples have 2 x 5V 3A windings and 2 x 5U4GB. aside from the fact that the paralleled filaments windings will need to be check for phase proper beforehand, what are the merits/demerits of each example or group?
it seems like B would wire in chassis the easiest.
thanks,
--pete
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I might be imaginative enough for this, but...
Aside from any wiring benefit, all look functionally the same to me; that is, 2 plates per winding end and all filaments at the same voltage level.
Barring some obscure failure mode, all 4 look like they'd "feel the same" to the rectifier tubes.
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thanks, those were my thoughts as well. one thing i was wondering about is that of the phase of the 5V filaments in split mode. if they are out of phase with respect to pin8 of both rectifiers, do things get noisier, or potentially quieter?
--pete
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In either mode, each rectifier still sees only 5vac (same as in pure parallel mode), so I don't think anything changes. I'd probably make sure the 5v windings are in phase, so there was no risk of heater voltage cancellation (you want the rectifiers to light up).
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I built a dual rectifier PS back in the '70s. It was the same as your "C" schematic except I only had one 5V winding, so phasing was no issue. Since I know this works fine I would use it again.
See page 3... Visio v0.001 :icon_biggrin:
http://home.comcast.net/~seluckey/amps/misc/76_Amp_Project.pdf (http://home.comcast.net/~seluckey/amps/misc/76_Amp_Project.pdf)
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thanks for the link steve...
looks like SL CAD v0.1 ??? :icon_biggrin:
--pete
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Well Pete now that you solved the problem, if you want to become a bit crazy ..... :icon_biggrin:
(http://www.geocities.jp/dave_group_japan/a1570b-2.gif)
Franco
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Those clever bastards!
The Altec is using the tube rectifiers in a bridge, which normally requires 3 separate heater windings, because only 2 of the rectifiers can share a 5vac winding at a single reference voltage; the other 2 windings each have to be referenced to the voltage applied to that individual diode.
They solved it by adding 5v taps "beyond" the ends of the winding whose voltage is being rectified. Saves on insulation costs over have separate 5v windings for the 2 tubes drawn closest to the transformer symbol.
Anyway, those are big class AB2 or class B2 power amps with 165w ~153w output power from a pair of very large power triodes, with grid current supplied by the 6W6 beam power tube cathodes. The 811A output triodes dwarf the 5R4 rectifiers.
(http://www.soundup.ru/images/stories/archive/Classic/pre-amplifier/altec-1570b-mono-block-power-amplifiers/altec-1570b-mono-block-power-amplifiers-13.jpg)