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.
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
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
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
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.
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.
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
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
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.
(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.
Attachments
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.
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.
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.
I was at a salvage yard maybe 20 years ago and I saw about 25 HP 200AB's and 200 CD's destined for the crush and melt process. The operator got about 50 of them from somewhere, paid someone to test them, and scrapped the "bad" ones. They had been left on a pallet, outside in the Florida rain. I bought them all for the melt value (I think it was about $3 each). I made one or two god ones by swapping tubes, and disassembled the rest for parts.
They were two different power transformers. One oscillator runs solid state rectifiers with 6AU6's and 6CW5's (200CD maybe?) the other runs a 5AR4 and 6K6's (200AB?)
Some of the power transformers were quite rusty, some were not, all worked. I gave the really rusty to a local metal recycler. I kept the end bells since they fit some open frame OPT's that I had. I built guitar amps with the rest. None of the amps ever died despite some of them running the power transformers far beyond the original intentions.
They were two different power transformers. One oscillator runs solid state rectifiers with 6AU6's and 6CW5's (200CD maybe?) the other runs a 5AR4 and 6K6's (200AB?)
Some of the power transformers were quite rusty, some were not, all worked. I gave the really rusty to a local metal recycler. I kept the end bells since they fit some open frame OPT's that I had. I built guitar amps with the rest. None of the amps ever died despite some of them running the power transformers far beyond the original intentions.
I'm in Europe so not easy import from USA
What would you think between these two :
electrophoresis power supply in vendita | eBay
Maybe the EPS1001??
What is the difference between one of these and a variac?
Thanks
What would you think between these two :
electrophoresis power supply in vendita | eBay
Maybe the EPS1001??
What is the difference between one of these and a variac?
Thanks
Last edited:
Those seem very expensive to buy and very expensive to ship within Europe. I would look at the US vendors and see how much they charge to ship to your location. Might be cheaper.
There is no comparison between these supplies and a variac. These are very sophisticated switching supplies with constant voltage, constant current and some also offer constant power outputs. Most also have a sensing circuit that disables the output if there is no load connected.
Perhaps something was lost in translation, but a variac is a variable autotransformer and does not give a dc output. And most variacs do not go much above the input voltage.
There is no comparison between these supplies and a variac. These are very sophisticated switching supplies with constant voltage, constant current and some also offer constant power outputs. Most also have a sensing circuit that disables the output if there is no load connected.
Perhaps something was lost in translation, but a variac is a variable autotransformer and does not give a dc output. And most variacs do not go much above the input voltage.
Yep, check the voltage and current parameters of the supply versus your needs. I also strongly prefer control knobs (twist type) for adjusting the voltage and limits. Some of the supplies use digital controls, like key in numerals, or up-down buttons to adjust things. One likes to be able to adjust a voltage quickly/easily while observing effects on an O'scope.
Yes but... not always. I have a couple of those where the control twist knobs "roll over". That means that if it's a 500V supply and you dial a bit past 500 it goes to zero. That's not so bad but if you're near zero and dial a bit past zero you get hit with 500V. That can have consequences
So like everything else, it depends and knowledge is key.
I agree with everyone else - older, regulated, HV supplies are a staple of hamfests - hard to justify scratch building one, unless funds are really, really, tight.
I got one of the heathkit lunch pail types for about $75 or so - looked new, provides 0-400 HV, - bias, and 6.3 volts, and had a pair of like new RCA blackplate 6L6GC as the pass tubes. Reselling the pass tubes might well cover the cost of a hamfest acquisition. One of the years at Dayton, I went up to Fair and grabbed a NOS Kepco supply for about $50.00 that goes 0 - 200 volts, has current limiting, some more 6.3 volts, and had a new GE 7581A in the pass tube spot.
The Chinese 6L6GC tubes seem fine as pass elements.
Win W5JAG
I got one of the heathkit lunch pail types for about $75 or so - looked new, provides 0-400 HV, - bias, and 6.3 volts, and had a pair of like new RCA blackplate 6L6GC as the pass tubes. Reselling the pass tubes might well cover the cost of a hamfest acquisition. One of the years at Dayton, I went up to Fair and grabbed a NOS Kepco supply for about $50.00 that goes 0 - 200 volts, has current limiting, some more 6.3 volts, and had a new GE 7581A in the pass tube spot.
The Chinese 6L6GC tubes seem fine as pass elements.
Win W5JAG
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.