What to do with a 1350 Volt PT

the thermionic watercooler

813 output trannies

Postby bsmif » Tue Jun 19, 2007 8:26 pm

What sort of OPT would I need? Is there any FAQ on figuring out what OPT works best? Sorry to sound like an idiot.
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Another application for those 1350 Volts!

Postby EWBrown » Wed Jun 20, 2007 5:06 am

Image

Februrary 29, 1932, Newark New Jersey:


After some extensive investigation that secretly took place nearly on a daily basis by special electric company command troops (including outside-hired detectives and detailed law-enforcement) supplemented by many others within company corporate command on overtime, the perp (lets just call him Mr. Mervyn Q. Zumwinkle) ...we clearly see this former customer facing the charges as he was convicted of electricity theft.

The photo was taken in the utility's 1350-volt high voltage glove-testng shop. Mr. Zumwinkle was a 48 year old world famous conductor who owed the electric company a grand total of $25.06 for lost (stolen) revenue including overdue and reconnection charges. It was found that he was turning back the dials on his 1890s Schellenberger Electricity Meter in his dark, dank cellar that was more creepy than the Addams Family could have ever thought possible. That style of meter is now known to be worth in the thousands of dollars. That's if you were to sell one today on E-bay.

At any rate, when Mr. Zumwinkle's heartbeat came to a rest and his blood stopped flowing as a result of his ultimate shock, in spite of his putting up much resistance, he still met his current fate. It is known that the watthour meter that he "frequented" proudly kept right-on-ticking for a goodly number of decades later. It is rumored to have been removed from service a few years ago, and it has since ended up for sale on E-bay.

Thinking about fiddling with your electric meter with today's skyrocketing energy costs? Then you better think about the potential consequences! Don't let the above happen to YOU!

/ed B inNH
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Postby kheper » Wed Jun 20, 2007 2:47 pm

What sort of OPT would I need? Is
there any FAQ on figuring out what OPT
works best? Sorry to sound like an idiot.


If you are talking about that SE 813 amp,
he uses a Tango XE 20s. They cost $416
per pair. They are very high-end, 20W SE
output transformers.

You could do better on e-bay. I have
seen some toroid SE outputs go for
a very reasonable price.
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813 OPT's

Postby bsmif » Wed Jun 20, 2007 4:20 pm

Would any 6K single ended opt work if rated to sufficient voltage? How do I figure out what voltage it would produce>

The edcors seem to be in the ballpark.

http://edcorusa.com/products/transforme ... -6_6k.html

Although I think one site said it needed to be 10K for Ultralinear use

http://edcorusa.com/products/transforme ... 8-10k.html
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Postby kheper » Wed Jun 20, 2007 5:21 pm

Those edcors are for push-pull, UL
tetrode/pentode amps, not SE triodes.

What type of amp are you making?

The plate to plate impedence is not
very important.

It would not be a simple task to use the
813s in UL mode. The plate voltage
in typical applications is 2500V and
the screen voltage is 750V. A PP
UL transformer with a %40 screen
tap will not work without ridiculously
dropping the voltage from the screen
tap of the transformer. If you dropped the
B+ to about 1200V, it would be
doable.

The following is a SE 25W 6.5k output
transformer -

http://edcorusa.com/products/transforme ... -6_5k.html
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Postby erichayes » Wed Jun 20, 2007 5:32 pm

This is another situation where the original Williamson circuit would be applicable--at least for experimentation purposes. Might sound like crap, as some TX tubes are wont to do, but at least it's doable on paper.
Eric in the Jefferson State
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My bad

Postby bsmif » Wed Jun 20, 2007 5:35 pm

Hmm, those figures sound more like a Jacob's Ladder than an amp. I do have an old Neon sign transformer....naaaaaah.

THis guy
http://homepages.ihug.co.nz/~rwillis/al ... _white.jpg

has some simple looking set-ups for an Ultralinear Triode where the voltages are arent higher than 900 Volts.

I'd love to figure out if there might be a way to simplify Millett's power supply though.
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Postby kheper » Wed Jun 20, 2007 5:42 pm

There is no such beast as a UL triode
amp.

The following is an 813 pentode run in SE
triode mode -

http://www.pmillett.com/813_se_triode_amps.htm

The following is an 813 pentode run in UL SE
mode -

http://homepages.ihug.co.nz/~rwillis/al ... _white.jpg
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That makes more sense

Postby bsmif » Wed Jun 20, 2007 6:13 pm

Of course! I didnt see "pentode" in his description but that makes more sense considering the power and connections. Boy the trick with the 813's seems to be the power supplies.

These big tubes seem to inspire lunacy
http://www.izzy-wizzy.com/audio/images/813amp2nite.jpg
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Postby SteveH » Thu Jun 21, 2007 7:12 am

All,
Well I have just started collecting parts for my 813 project; so I will toss in my $0.02.
I would go with Mr. Willis's recomendations of running the tube somewhere around 900v @ 90mA. Your transformer would be more than enough to get you close. Notice though that this gives you somewhere around 35w in SE UL; so those 25w Edcors are not going to be enough.
Oddly enough, I had just emailed Edcor earlier this week to inquire how much it would cost to get a 50w version of those OPT's made. I'll keep you informed, as the more the merrier (and the cheaper !).
I've affixed my schematic. I haven't completely figured out the PSU's yet; but that is my goal in the next week. For B+ I am thinking of using 6D22S's, as they will supply more than enough current, and offer slow start. Naturally, I'd love to put in some 816's; but real estate concerns I think might keep them away (time delay, 5vct heater supply, etc). As far as the power transformer, I will be ordering the 550v toroid from Antek. It will give me 1.1kVct @ 300mA, and (2) 6.3@ 5A - all for the sum of $42/ea :D. I'll use the 6.3 lines to supply heat to the rectifiers and driver tube; while I will need an additional 15v @ 5A transformer for the heaters, as I think I will lose about 5v though the rectification/regulation.
On that note, I will be using a SS rect/regulation system for the heaters; paArt showed me a very nice schematic; once I get a copy I will post it here.
If anyone has suggestions on a PSU scheme, please let me know. It is a catch 22, as HV caps aren't cheap, nor are they small...But I guess that's kinda the point to begin with...hehe

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Postby EWBrown » Thu Jun 21, 2007 8:20 am

Do you mean to put 900V on the 6SN7 B+ ? :o

Get the fire extinguisher ready Yellow_Light_Colorz_PDT_11

As far as the OPT goes, I think Hammond has something appropriate over at AES, the big 11 pounder 1929SEA:
It's 30 watts and 100 mA max, so it may be a tad "light" for this circuit...

(casually lifted from the AES site)


TRANSFORMER, OUTPUT, SINGLE-ENDED, HAMMOND, 30 WATT

P-T1629SEA


New and improved version, higher power handling smoother frequency response, easy to use secondary tap.
Over designed for single ended tube output circuits (triode, tetrode or pentode tubes).
Enclosed (shielded), 4 slot, above chassis Type "X" mounting.
Frequency response at least 20 Hz. to 20 Khz. at full rated power (+/- 1 db max. ref. 1 Khz.)
Insulated flexible leads 8" min.
Includes a 40% screen tap for Ultra-Linear operation (if desired).
High quality laminations, (M6) grain oriented silicon steel
Core is gapped to reduce core saturation in Class-A circuits.
For general purpose or replacement use in single ended tube output circuits see our P-T125SE series.

Specifications
Audio Watts: 30
Primary Impedance (Ohms): 6500
Primary Inductance (H): 55
Primary Max DC Bias(mA): 100
Secondary Impedance (Ohms): 4/8/16
Suggested Triodes: 211, 811A, 572B, 845
Suggested Pentodes: 6AQ5, 6V6, 6L6, 807, 5881, 6550, EL84
Hipot Test (VRMS): 2,000 Weight: 11 lbs



I've got a NOS NIB pair of these "big jugs" Yellow_Light_Colorz_PDT_08 and the sockets, snagged 'em cheap at a hamfest last year.
Just like Flip Wilson used to say, "the devil made me do it" Yellow_Light_Colorz_PDT_03

Haven't yet decided twhether o use them for RF, or audio, or put 'em up for adoption...

/ed B in NH
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Postby SteveH » Thu Jun 21, 2007 8:31 am

Don't think the 6SN7 could take 900v ? I can't see any better way of going about it; so if you have any thoughts please let me know. A voltage divider circuit wouldn't be the best idea here I don't think ?
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Postby EWBrown » Thu Jun 21, 2007 11:26 am

Speaking of Tesla Coils:

http://tesladownunder.com/index.html

the ozzies in the land down under are gettin' restless :o

Image


And here is a little more Tesla "mischeif" from much closer to home:

http://www.hauntedfrog.com/gt/movies/20 ... aShow.html


/ed B in NH


Image
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Postby EWBrown » Fri Jun 22, 2007 5:08 am

I'd keep the 6SN7 B+ voltage around 450V or less. 900VDC is kinda like playing Russian roulette with a semi-auto :o Yellow_Light_Colorz_PDT_04

The alleged 1500V peak indicated in the tube manual is an instantaneous "flyback" induced peak during TV vertical sweep service, and 450 - 500VDC is the maximu, safe B+, and the actual plate voltage should be around 300-330 VDC, maximum.

Getting 900V B+ isn't too difficult, use a PT with 400-0-400VAC , 200mA and a SS full wave bridge across the entire 800VAC.

Of course, with twice the normal DC voltage being generated, a sacrifice has to occur, the trannie is now going to have half the current rating as with the more "traditional" rectification scheme, so the actual current will be 100 mA and not 200 mA, so this would apply to a sinngle channel's requirements.

Use the centertap as a 450V (approx) tap, and the PSU caps can be connected in series, with the CT being the common point. This allows use of 600VDC rated caps (500 would be pushing the envelope), and also that would give you the 450V (approx) source for the 6SN7. The plate resistor would have to be re-calculated and would be somewhere around 22-27K.

An experiment: Connect the two 6SN7 sections in parallel, and halve the plate and cathode resistor values.
This will draw 2X the plate current, and the effective transconductance would be doubled, and the effective plate resistance would be half, and so the overall gain would renain the same as with a single section.
According to the VTL tube book, this also lowers the noise floor and increases the overall dynamic range.



/ed B in NH
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Postby SteveH » Fri Jun 22, 2007 6:12 am

Ed - that sounds excellent. I am going to draw up a schematic this evening and see what I can come up with.....I'll post it up just to make sure I completely understand what ya are telling me.
That said - I want to go with tube rectification..Just my thing I suppose. Here's a model that I did in PSUdII

Image

So...Let me see if I have this straight. I would wire both ends of the transformer to the bridge as shown. However, instead of 'normally' connecting the CT to ground (thus giving me 400v B+), I would put caps in series, taking the voltage from the CT and placing the negative terminal of the cap back to ground. Sound right ? Then the filtered DC that I got out of the CT would then be my B+ for the driver tube.
I suppose the tricky part here will be where do I use as ground for these caps ? The ground coming out of the bridge ?

The transformer in there would be this one:
http://www.toroid-transformer.com/AN-4T450.pdf

At 800v, I would be able to get 416mA out of it I believe. Is that correct ? I calculated it by:
VA Total = 400VA
6.3V*10A = 63VA
333VA/800V = 416mA

So would I get 1/2 of this value then ? Either way, I will have more than enough headroom :D

The chokes would be Hammond 158M's
Thanks,
Steve
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