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Old 13th November 2005, 11:54 AM   #21
VT67 is online now VT67  Belgium
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Default Transformer

Anybody here that has a source for a 45V-0-45V / 5-10VA toroid transformer.
The lowest VA rating I can find with those secondaries is 160VA, and that is a bit overkill I figure?

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Old 13th November 2005, 03:30 PM   #22
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Default Re: Transformer

Quote:
Originally posted by GeWa
Anybody here that has a source for a 45V-0-45V / 5-10VA toroid transformer.
The lowest VA rating I can find with those secondaries is 160VA, and that is a bit overkill I figure?

Regards

You need only one winding of ~45 VAC. So you can use a tranny ranging 18-0-18 to 22-0-22.
These should be no problem to find in that VA range.

cheers.

(please correct me if I got confused between my projects )
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Old 13th November 2005, 03:56 PM   #23
VT67 is online now VT67  Belgium
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Quote:
You need only one winding of ~45 VAC. So you can use a tranny ranging 18-0-18 to 22-0-22.
Now that you mention it. Just had a quick look at the schematic and it's indeed only "1" secondary winding.
What's even worse, I have two 22V-0-22V / 35VA trannies in my goodies cupboard. I really feel stupid now

Thanks for the hint Hanzwillem

Regards
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Old 13th November 2005, 04:44 PM   #24
Franz G is offline Franz G  Switzerland
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Quote:
I have two 22V-0-22V / 35VA trannies in my goodies cupboard. I really feel stupid now
Why stupid? Just use two secondaries in series, resulting in 44 VAC, what is perfect for the anode voltage!

BTW: I use one single torroid, about 165VA. It is including 14.8-0-14.8V (LM3875), 17.6 and 19.8 in series for the anode voltage. Then I added some windings for the 6V part (about 60 windings in my case, just try 20 windings, measure under load and calculate the needed windings, its linear).

It is a good idea, when you use the small case and relatively small heathsinks, not to use too high voltage and to much gain for the LM3875.

Franz
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Old 14th November 2005, 08:11 AM   #25
digi01 is offline digi01  China
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Quote:
Originally posted by Hanzwillem
There seems to be an error in the silkscreen of the PSU board.
I suspect D1,D2,D3 to be printed the wrong way. I don't see this work as a proper bridge as it is drawn at the moment...

Yes,there are silk layer missed of bridge and delay parts,I am so sorry for all troubles.I will release a 'PATH' for the psu board soon.please keep it for a while.

to wim,sorry for delay.because I couldn't surf net during weekend.


P.S.
the attached photo is the connection of 'T' network.
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Old 14th November 2005, 08:25 AM   #26
digi01 is offline digi01  China
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Default Re: Transformer

Quote:
Originally posted by GeWa
Anybody here that has a source for a 45V-0-45V / 5-10VA toroid transformer.
The lowest VA rating I can find with those secondaries is 160VA, and that is a bit overkill I figure?

yeah I have the same problem to find a proper transformer.I use a 20VA 8VAC wallwart directly powered the tube filaments and delay.A step-up transformer(200VAC to 24VAC,in reverse) converted the 8VAC to about 73VAC.


Zang
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Old 14th November 2005, 12:14 PM   #27
wim is offline wim  Netherlands
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Mayby i missed something, but what is the need for a 45-0-45 VAC trafo? I assume you will put the windings paralel to get about 62 VDC after rectification?

Why not a trafo between 18-0-18 VAC and 22-0-22 VAC, and put the windings in serie? These trafo's are common with a much lower VA rate.

Or do i mis something?
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Old 14th November 2005, 12:20 PM   #28
VT67 is online now VT67  Belgium
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No Wim, you got the point exactly. I think I'm the nitwit who started this confusion. I was under the impression that a 45-0-45 trafo was needed. Look at post #23.
Sorry for all this

Cheers
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Old 14th November 2005, 12:24 PM   #29
wim is offline wim  Netherlands
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Okee GeWa, now you can choose a suiteble trafo. i take 18-0-18 VAC. RS Components have them in very small VA ratings (cheep and compact). Succes.
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Old 16th November 2005, 05:30 AM   #30
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Quote:
Originally posted by GeWa
I was under the impression that a 45-0-45 trafo was needed
For the tube which needs something between 35-0-35 & 100-0-100 @ 15+ mA or so...

dave
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