<800v? Power supply - Page 1
Forum section: electronics / testgear

author: cowasaki
author_rank: Frequent Contributor
timestamp: December 13, 2020, 07:16:52 pm
content: I build valve amplifiers and I would like a power supply that can provide the HT voltage for the tubes. At the moment I can get any voltage I need but using a 240>24V backwards into a 240>54V which gives 540V AC but with a variac that goes from 0 to 115% I can get 621V AC. Once rectified this gives me 0 to 700 odd DC volts. Using a bulb limiter as well I can current limit BUT this is not ideal......What I would like is a power supply like my normal bench supplies but that goes up to 500V DC (as a minimum) going up to 800V or 1000V would be even better but being able to set a specific limit say 80mA or 200mA with the supply not affecting the current until it hits the limit.I've looked but they all seem to stop well short. Am I just looking for the wrong supply? I would go second hand if there is something older. I've just come into some money so I thought I might treat myself.Any suggestions? Oh and I do not need symmetrical rails just straight DC volts with a limiter. (I can do the "without a limiter" version already).

author: bob91343
author_rank: Super Contributor
timestamp: December 13, 2020, 09:26:21 pm
content: I have just the unit for you. Unfortunately it's inaccessible due to its size and weight and the fact that I am in California.It's a Dressen-Barnes 62-117 boat anchor tube supply with voltage and current meters and regulated outputs of 0 - 300 V at 200 mA and 0 - 500 V at 300 mA. The two outputs can be put in series, yielding 0 - 800 V at 200 mA. There is also a variable ac for heaters. No current limiting. Runs from 120 V 60 Hz.It's very old, perhaps 50 or more years but seems to work.Will cost a fortune to ship.

author: cowasaki
author_rank: Frequent Contributor
timestamp: December 13, 2020, 09:36:48 pm
content: What does it weigh?Yes that's the type of thing I could do with :-)

author: HighVoltage
author_rank: Super Contributor
timestamp: December 13, 2020, 09:52:10 pm
content: From time to time you can find an old HP or Agilent used power supply on ebay, good for 1000V.But they do not show up often.You can also look for a German company called "FUG"They make very nice high voltage power supplies with current limiting ability.These also show up on ebay from time to time in very good conditions.

author: cowasaki
author_rank: Frequent Contributor
timestamp: December 13, 2020, 09:54:31 pm
content: Quote from: HighVoltage on December 13, 2020, 09:52:10 pmThanks. I will take a look.

author: PartialDischarge
author_rank: Super Contributor
timestamp: December 13, 2020, 09:57:53 pm
content: Quote from: HighVoltage on December 13, 2020, 09:52:10 pmTrue, recently I got a 6500V model and really like it.

author: cowasaki
author_rank: Frequent Contributor
timestamp: December 13, 2020, 10:00:06 pm
content: Quote from: MasterTech on December 13, 2020, 09:57:53 pmYes I've found a few. They are in France so I need to check when they stop posting for Christmas so that I can receive it before Brexit kicks in..........

author: HighVoltage
author_rank: Super Contributor
timestamp: December 13, 2020, 10:09:32 pm
content: Nice that you found one.Most of the FUG power supplies in this voltage range use special high voltage connectors, called SHV.So make sure you order some high voltage cables with SHV connectors as well to use the power supply.

author: cowasaki
author_rank: Frequent Contributor
timestamp: December 13, 2020, 10:16:04 pm
content: [ Specified attachment is not available ]Quote from: HighVoltage on December 13, 2020, 10:09:32 pmIs that what these are:[ Specified attachment is not available ]

author: HighVoltage
author_rank: Super Contributor
timestamp: December 13, 2020, 10:37:26 pm
content: Yes, that one requires 2 pieces SHV cablesLike this one:https://de.farnell.com/huber-suhner/11-shv-50-4-1-133-ne/hf-koaxial-shv-stecker-50-ohm/dp/2473827

author: cowasaki
author_rank: Frequent Contributor
timestamp: December 13, 2020, 10:42:15 pm
content: Quote from: HighVoltage on December 13, 2020, 10:37:26 pmThanks.... That's a lot of extra money. Found these thoughhttps://www.ebay.co.uk/itm/Alligator-clip-Banana-to-RP-BNC-SHV-5000V-High-Voltage-1M-RG6-Test-Power-Cable/223069701927?hash=item33effd8727:g:aVgAAOSw4ZxbUp4F

author: HighVoltage
author_rank: Super Contributor
timestamp: December 13, 2020, 10:51:39 pm
content: The "Huber Suhner" connectors from Farnell are just top notch quality and have a high price.It was more meant to be for you to know what to look for.The ebay connector you found will work well with the FUG power supply.

author: cowasaki
author_rank: Frequent Contributor
timestamp: December 13, 2020, 10:56:40 pm
content: Thanks. I will only need the HV connector on one end so the eBay cheep ones will probably do it.

author: David Hess
author_rank: Super Contributor
timestamp: December 13, 2020, 11:46:34 pm
content: It will be difficult to find a more reliable and realistic solution than a variac and step-up transformer.

author: cowasaki
author_rank: Frequent Contributor
timestamp: December 13, 2020, 11:48:42 pm
content: Quote from: David Hess on December 13, 2020, 11:46:34 pmThats what I'm using now. I want a current limiter rather than just a bulb

author: David Hess
author_rank: Super Contributor
timestamp: December 14, 2020, 12:32:56 am
content: Quote from: cowasaki on December 13, 2020, 11:48:42 pmJust designing a 800 volt current limiter which will not self destruct is quite a challenge. It can be made easier with fold-back current limiting which lowers power dissipation in the power transistors but this is not suitable for all applications.One method I would consider is an AC output with current limiting on the primary side of the step-up transformer where the lower voltage makes things easier. This only requires a fault protected and current limited audio amplifier to drive the step-up transformer.

author: bob91343
author_rank: Super Contributor
timestamp: December 14, 2020, 06:32:36 am
content: The Dressen-Barnes probably weighs at least 50 pounds.