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Old 20th February 2016, 01:39 AM   #21
Tubelab_com is offline Tubelab_com  United States
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There is at least one simple way to make a useful HV bench PSU: Just build out a rectifier/filter system with low impedance, then put a variac in the incoming AC line. The output voltage will be about as stiff as a typical tube amplifier power supply, which can actually be beneficial during circuit development
I built one like this about 15 years ago. A big variac on the input of a 1KVA 120 - 120 to 240 - 240 industrial control transformer hooked up backwards. Each of the 240 volt primaries (used as secondaires) had its own solid state bridge and big a$$ electrolytic (2400 uF 450 V) to create a pair of simple 0 to 300 volt supplies. These could be paralleled (no need with over an amp available) seriesed (for 0 to 600V) or used independently for circlotron experiments. The major disadvantage was size and weight. The danger......BIG BANG if accidentally shorted out. Fuses on the secondary side don't blow....they EXPLODE!!!!! Fuses on the primary side are too slow with 2400 uF of stored energy on the output.

I had (and still use) the previously mentioned Knight KG-664 (smoking amp's first picture). I only used the BIG BANG power supply for big stuff......over 100 Watts. The KG-664 is still my go to power supply unless I need more power.

I got a Fluke 407D on Ebay for $25 (and $45 shipping) in "untested" condition. I opened it up before plugging it in to find a broken switch which I glued back together with JB weld. The power supply worked and I still use it today even though it still has all the original tubes and "bumble bee" caps in it. It will go into oscillatory convulsions when grossly overloaded. But otherwise works good. It uses 5 or 6 807's for pass tubes, and has multiple taps on the secondary of the transformer to reduce dissipation in the pass tubes.

I also have one of the HP6448B's that smoking amp mentioned. It uses a triac controller that works like an incandescent light dimmer on the input of a 40 pound transformer. Think of it as an SMPS that switches at 120 Hz.....slow. The control loop's response is like 500 mS. Your circuit is on FIRE before the current limiter kicks in......BIG BANG on STEROIDS. There is 1000 uF internally across the output, to make sure that stuff blows up. This power supply gas blown electrolytics in half, vaporized resistors and PCB tracks, blown the guts out of some tubes, and set an OPT on fire! Despite these minor drawbacks, I still use it a lot.....it replaced the variac / industrial transformer monster.

Some of my designs use all three of these power supplies simultaneously. When I was in Florida, simultaneous use of all near their power limit would trip the 15 amp bench breaker, and occasionally the 20 amp house breaker, so I was at my limit. This was done extracting 525 watts out of one of Pete's big red boards. I now have about 10 KW of power available so I will built a bigger power supply some day.
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Old 20th February 2016, 02:28 AM   #22
smoking-amp is offline smoking-amp  United States
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Well, I see the HP-177A power supply sold for $107.50 after 25 bids!

And the $15 ISCO sold. A bunch more of the ISCO's are listed in the $45 to $60 range.
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Old 20th February 2016, 03:55 AM   #23
HollowState is offline HollowState  United States
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Well, I see the HP-177A power supply sold for $107.50 after 25 bids!
Actually the correct model number is 711A. Seller dyslexia? I was watching it, but didn't need it that bad since I have several others. And someone snagged the Kepco 615 at $175
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Old 20th February 2016, 09:15 PM   #24
DualTriode is offline DualTriode  United States
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Smile This is DIY so have at it

Hello All,

Plus 1 to both Tubelab.com and Smoking-Amp.

For the time and money there are too many old school professional lab power supplies to build a test lab supply.

However this is DIY so have at it.

I use a HP 6253A; dual 0-20v, 3a for heaters and a HP 6209B; 0-320v, 0.1 amp for B+ duty. This test gear has the benefit of being able to operate at constant voltage or constant current. I do like to adjust the output voltage with a maximum current setting as “Oh S**t” protection.

DT
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Old 21st February 2016, 12:53 AM   #25
Tubelab_com is offline Tubelab_com  United States
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BIG A$$ amps require BIG A$$ power supplies. I reached the limit on the HP6448B back in Florida. I turned some of the internal adjustments in my HP so that I can hit 650 volts at 1.7 amps. This was also the limit on my bench power.

I am building a new lab, and the 240 volt 200 amp breaker panel is 6 feet from my bench. A fat piece of Romex and a new breaker gets me all the power I want!!!! I have a target of a 1KW tube amp in the back of my mind, and over the years I have collected all of the expensive parts......I'm going to need a bigger bench supply. It would also be nice to replace 3 or 4 old dinosaurs with one nice power supply, but I can't get what I want at Walmart, so I'm going to have to build it.....no hurry though.

I got 3 X Sorensen DCS33-33E SMPS that do 0 to 33 volts at 0 to 33 amps. They are 1 RU tall, weigh about 15 pounds each, are IEE-488 bus controlled, and can be wired in series or parallel.....find me a tube I can't light up with those.
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Old 21st February 2016, 04:43 AM   #26
DualTriode is offline DualTriode  United States
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Smile Home brew Lab

Hello TubeLab.com and All,

There are no dreams of kilowatt tube amplifiers here.

Connecting and controlling the instruments and test protocols by way of computer remote Interface was science fiction not long ago.

Will the Home Owners Association allow the kitchen range electrical outlet in your Home brew Lab?

DT
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Old 21st February 2016, 05:58 PM   #27
smoking-amp is offline smoking-amp  United States
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Just a couple of these $40 Lambda PF1000 units off Ebay, and you can run 2000 Watts 720V (360V+360V) on an extension cord from the laundry room.

(low EMI, sinusoidal current draw using PF, power factor, correction) But I think any HOA would allow a welding/dryer outlet in the garage/lab anyway.

Would need a big 240V : 240V-240V industrial xfmr to provide V isolation for the PF units still.

Lambda PF1000A 360 Module PFHC Module 500W 1000W | eBay

-----------------------

Or use two Xantrex XHR-600-1.7, those are PF corrected, and isolated.
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Old 21st February 2016, 09:15 PM   #28
Tubelab_com is offline Tubelab_com  United States
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Will the Home Owners Association allow the kitchen range electrical outlet in your Home brew Lab?
Where we live now there is no HOA, and no city either. We had a house built and the only inspection was the one we did before we moved in...A far cry from the code enforcement cops in Florida.

The builder required a licensed electrician to do all the wiring. The electrician followed all of my requests, but I left the basement wiring empty except for the required lights. I can do what I want far cheaper.

I will run two phases of 120 volts to my bench and a 240 volt outlet. I figure that 240 at 20 or 30 amps will be sufficient for anything I care to build, plus a pair of 120 volt circuits at 20 amps each for the lab. There will be separate 20 amp run for all the music studio stuff.
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Old 21st February 2016, 10:34 PM   #29
dgta is offline dgta  United States
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Originally Posted by HollowState View Post
Actually the correct model number is 711A. Seller dyslexia? I was watching it, but didn't need it that bad since I have several others. And someone snagged the Kepco 615 at $175
711A not recommended.

I have one and I went through it and replaced caps, tubes, etc. years ago. It worked fine for a short while but eventually the transformer crapped out and it's basically irreplaceable. And it wasn't from any abuse, IIRC transformer developed an internal partial short between windings.
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Old 21st February 2016, 11:06 PM   #30
HollowState is offline HollowState  United States
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711A not recommended.
Of course there's always exceptions but most of the older Hewlett Packard transformers, which were built by PAECO (Palo Alto Electric Company), held up very well. Paeco was, or became, part of HP. I've been using and selling HP test equipment for over fourty years and have only seen one 200CD PT go bad and maybe one other in the distant past. But that's all in all those years. The 711A was not my favorite because it was only 100mA. BTW, the electrolytic can capacitors that HP used lasted a very very long time too. I can't remember the last time I replaced one.
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