Electrophoresis power supplies for HV DC!

[nuke]

I mentioned this in another topic, but if you're looking for a source of adjustable, regulated, high-voltage DC, you might look at a used electrophoresis power supply.

Electrophoresis is a technique for DNA sequencing, where samples are injected into plates coated with gelatin, and a high DC voltage is applied across the plate to draw the molecules out. It leaves a track of banding which is visible indication of the ACGT groupings in the DNA.

There was a time when it was all the rage, and newer better equipment has come along.

If you check on eBay, there's lots of electrophoresis power supplies out there and they are dirt cheap.

These power supplies usually provide 500v of regulated DC, some as much as 1000v and *amazing* levels of current, like 200ma at 500v. The electrophoresis process requires DC, but not as clean DC as one would need to power sensitive audio. But they provide filtered DC, it's just a little too "hashy" for audio.

I bought one some time ago, for about $50 and shipping, so under $100 for the whole deal.

The unit is all analog, with analog meters, and the circuit board include op-amp based voltage and current regulation, safety circuit, and drives the meters on the panel.

The operating principle is a simple UJT oscillator, which drives a pair of SCRs through a pulse transformer. The SCR's "chop" the cycle of the 60hz mains voltage, which is then fed into a 1:5 step up power transformer. The wider the slice of AC, the higher the voltage. That's then rectified, filtered with a couple of 600v electrolytic caps and fed through the safety and current sensing and out the banana jacks on the front panel. The knobs allow for voltage and current adjustment, so it can run constant voltage or constant current.

I'd look for an analog unit, as they're easier to hack and fix. The microprocessor based ones probably aren't too bad, but they may be more difficult to tinker with.

They're excellent for cap testing and I've used them to power a tube matching jig that I never got around to fully building. Clean enough power for that.

[TUBEDUDE]

Interesting. How's the radiated noise? Is that an issue for amp use?

[cdemike]

Sounds great for a test rig! If someone wants to try this in an actual amp, it may be a good idea to isolate the first node from the power supply via a choke or a resistor between the need for filtering out the high-frequency hash and the absence of any kind of sag given that it's regulated.

[nuke]

The one I have, the output is filtered by two 20uf 600V electrolytics. It's not pure pristine power, but I've powered stuff with it for experiments and what not.

Really good for testing capacitors at voltage, and for forming/re-forming electrolytic caps. I've got a pile of NOS electrolytic caps. I won't put them in other people's amps, but I'll use them for my own projects. Just put them on and let them go for 24 hours at high voltage and check to see if they're leaking at all.

I've been trying to figure out how to make it a very clean power supply. A simple way would be to just bypass the entire electronics, and feed the step up transformer with a variac. Could easily build all that in the existing case. Would be a nice clean adjustable HVDC power supply, just not a regulated one.

They're so cheap though and tons of them out there.