What to do with a 1350 Volt PT

the thermionic watercooler

Postby EWBrown » Fri Jun 22, 2007 7:54 am

Your numbers of 800V @ 416 mA, calculated for the trannie are correct. In addition, they state that on 60Hz power, the actualy VA capacity is 10%-20% higher, so you should have plenty of power "overhead", as the circuitry should draw around 200 mA average, for both channels.

First of all, make sure that the chokes can handle the high voltage, and not suffer from winding-to-core breakdown. Ditto for the 6D22 filamant trannies. These trannies are usualy hi=potted at 1500VAC / 2121 VDC, for dielectric withstand, but this is done at low current and for a relatively short test time.

The 158Ms are rated for only 400VDC:
FILTER CHOKE, OPEN BRACKET, HAMMOND, 10 H, 100 mA

Specifications
Rating: 10 Henries, 100 mA
Max. VDC: 400
Resistance: 262 ohms
Mounting centers: 2.81" U-frame
Weight: 1.3 lbs.




(I just thought of an easier simpler method, so I just edited out a few unnecessarily detailed and lengthy paragraphs)

Use the circuit that you already have, just connect the Secondary's CT to its own C-L-C or C-R-C filtering, in order to generate the half-B+ (450VDC) power for the driver stages.

The power trannie I had in mind was the Triode P782 or the Hammond equivalent, but the Antek toroid should be perfect, and less costly, and they do have available some even higher current versions. The 813s will need some seriously hefty filament power as well, either Hammond or Antek should have something usable here.

BTW, I just ordered (on 6/21) an Antek 4T360 for some future "ST70" project.

/ed B in NH
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Postby SteveH » Fri Jun 22, 2007 9:08 am

Ed,
Gotcha. Honestly I think I might go down in VA then, as I am planning on doing monoblocks. The heaters for the 6D22S's I was just going to use the heat windings on the Antek transformer...no ? It has two 6.3v windings @ 5A ea.
You are right about the chokes though.....I didn't look at the voltage rating. Guess Hammond is out !
I understand ya now on the CT filtering. So I will use the same ground that comes out of the diode bridge - correct ?
On a side note, I highly recomend Antek's transformers...I find them to be really high quality; especially for the price.
For the Heaters,this circuit was suggested to me by paArt:
Image
Maybe overkill for 10v@5A requirement ?

It is a shame in looking at my B+ available current (especially coming out of a bridge of 6D22S's !), that I don't want PP 813's. I guess 350wpc just isn't for me :D

Thanks again,
Steve
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Postby EWBrown » Fri Jun 22, 2007 11:50 am

The same ground (negative side of the bridge output) works for the half-B+ output, as well.

The regulator circuit looks like it's designed for 5V output, you'd have to change the 12.6VCT tranny to something around 20-25 VCT, in order to deliver 10VDC @ 5A per tube, and figure in a little current overhead for safety's sake. 2N3773s might be better pass transistors, they are basically 2N3055s "with an attitude".

The filaments gobble up 50 watts each! :o

/ed B in NH
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Postby SteveH » Fri Jun 22, 2007 1:38 pm

Ed,
Thanks again for the help. This really makes my day.....I feel that it is an excellent solution.
In any event, here is the text from the schematic:
"...The high current regulator below uses an additional winding or a separate transformer to supply power for the LM317 regulator so that the pass transistors can operate closer to saturation and improve efficiency. For good efficiency the voltage at the collectors of the two parallel 2N3055 pass transistors should be close to the output voltage. The LM317 requires a couple extra volts on the input side, plus the emitter/base drop of the 3055s, plus whatever is lost across the (0.1 ohm) equalizing resistors (1volt at 10 amps), so a separate transformer and rectifier/filter circuit is used that is a few volts higher than the output voltage. The LM317 will provide over 1 amp of current to drive the bases of the pass transistors and assuming a gain of 10 the combination should deliver 15 amps or more. The LM317 always operates with a voltage difference of 1.2 between the output terminal and adjustment terminal and requires a minimum load of 10mA, so a 75 ohm resistor was chosen which will draw (1.2/75 = 16mA). This same current flows through the emitter resistor of the 2N3904 which produces about a 1 volt drop across the 62 ohm resistor and 1.7 volts at the base. The output voltage is set with the voltage divider (1K/560) so that 1.7 volts is applied to the 3904 base when the output is 5 volts. For 13 volt operation, the 1K resistor could be adjusted to around 3.6K. The regulator has no output short circuit protection so the output probably should be fused. .."

Now, I don't know about the additional supply for the LM chip.
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Postby sorenj07 » Fri Jun 22, 2007 11:42 pm

For the HV schematic you posted earlier, what happens if you scratch the resistor at the end?

Also, I'm not positive, but isn't it objectionable to have two LC filters at exactly the same frequency? Wouldn't he want to switch up cap values or something?
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Postby SteveH » Sun Jun 24, 2007 3:39 pm

Hrmm. Well I dunno about the PSU design element too much.

That said, the resistor at the end is to bring the B+ down to 900v.
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TEK Tranny Info

Postby EWBrown » Fri Dec 07, 2007 1:10 pm

Found this on Pete Millet's site:

http://www.pmillett.com/Tek_xfmrs.htm

Lotsa useful info on tthe classis TEK power trannies. Maybe I can ID those which I've scavenged recently from a power supply carcass.

The two that I have were from the carcass of a Tek 555 power supply.

120-127-01 and 120-128-01 Price was free (part of the Great Plinker Haul).

/ed B in NH
Last edited by EWBrown on Mon Dec 10, 2007 6:46 am, edited 1 time in total.
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Postby SteveH » Fri Dec 07, 2007 2:12 pm

Interesting stuff.
I've just about finished getting all of the parts I need; so construction should begin shortly.
The problem I have now is that anything over 600vdc is going to fry my DVM....
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