Re: zino13
- From: "West" <nospam@xxxxxxx>
- Date: Fri, 30 Nov 2007 02:38:27 GMT
"Peter Wieck" <pfjw@xxxxxxx> wrote in message
news:260f5e8d-76b6-48ea-8f2a-7de7336fdc68@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
On Nov 29, 3:42 pm, Peter Wieck <p...@xxxxxxx> wrote:
On Nov 29, 7:46 am, zino13 <zino13.194b...@xxxxxxxxxxxxxxx> wrote:
Greetings to you All
Just joined the board
I'm doing a rebuild/ mod on a magnavox cosole pull.
It has the....... 2- 6EU7 input/phase inverter tubes,
4- 6V6GT output tubes
1 6CA4 rectifier tube.
I'd like to beef up the power transformer how large can I go?
and Where could I purchase?
Zino:
If all you are doing is a very modest modifications there may be no
need to "beef up" the power transformer unless you perceive it to be
seriously overheating as-found. Even there, do not write off the
existing unit until you have at least changed the filter-caps,
replaced any paper caps and otherwise cleaned up the unit on your
first pass (in other words, rebuild it "to spec. first). You might
find out that with good filters the current draw is significantly
reduced.
One other (small) expedient would be to install a solid-state
rectifier ILO the 6CA4. That is a full-wave rectifier, so you will
have to be careful about voltages and how you set up a SS rectifier
(no real trick, just some care) but you would save 1A of current. So,
it gets down to your "mods". If you are adding tubes or installing
heavier output tubes (each 6V6 is 0.45A), then you would calculate
based on your final tube count and intended uses, required B+ voltage
and so forth.
It seems like from what you have written that the transformer has one
filament winding and one HV winding, and perhaps that the HV tap is
center-tapped. No schematic, pure speculation - wild guess on my part.
If so, then you could go to the Hammond site and pick from what is
available there based on what you have (filament tap(s)) and HV AC
secondary). You could even pick a transformer with a separate
rectifier filament winding - if that fits your intent.
How big "can" you go? No limit outside your pocketbook. How big
"should" you go? Possibly not at all depending on your ultimate
intentions.
But you are right to ask, Magnavox did not exactly over-design their
power transformers. Even though they were a bit more conservative than
Zenith. Faint praise, that, however.
Just for your information:
6EU6 = 0.3A filament current x 4 = 1.20A
6V6 = 0.45A filament current x 2 = 0.90A
6CA4 = 1A filament current x 1 = 1.00A
________
3.10A total
filament current (calculated)
370DAX
370DAZ
378CX
Are Hammond part-numbers that fit the calculation superficially and
without additional information.
Look here for much more and better info:
http://www.hammondmfg.com/300series.htm
And, of course, Hammond is not the only fish in the sea, but are
amongst the lowest cost-for-reliability.
Peter Wieck
Wyncote, PA
WHOOOPSSSSS!!!
4 x 6V6 @ 0.45A = 1.8A
2 x 6EU6 @ 0.30A = 0.60A
1 x 6CA4 @ 1.0A = 1.0A
Total is 3.40A
Doesn't change the suggested part numbers, however based on
superficial results.
Peter Wieck
Wyncote, PA
Relax big boy. If someone asked you for the time do you give them a
discourse on how a watch is made? No wonder why Mrs.Wieck sold the
encyclopedias.
west
.
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