Precipitator Failure

[Mark Rowley]

I'd reattach the current limiter until you're familiar with it's operation during neutron production. Operating a precipitator psu is somewhat different from a iron-core transformer so it's best to become familiar with its differences before attempting any modifications.

Fwiw, I've never altered the limiter on the 30kV unit so you're firmly in uncharted territory with that one.

Lot's of posts about the precipitator including the potentiometer issue. Search "precipitator" and you'll get all the old posts. Rex put together a stellar report on how they work including schematics. Well worth reading.

Mark Rowley

[Alan Sailer]

Richard,

The question you ask are good questions. I also have never bought a new wire-wound ten turn pot.
Not that it makes any difference, but I have used them in around twenty projects without any problem.

It is also a 10K pot just like the OEM unit. The pot was applied with teh correct polarity. Checked twice before soldering.

As far as linearity or skips that is not an issue in this case. The pot was turned to minimum resistance before
I turned on the supply. There was no adjustment made, the supply simply arced and died. Both output transistors dead.
Traces leading from the transistors vaporized.

If you could turn on the unit slowly with a Variac I'd try more experiments. But it's designed to boom! on.

Mark,

Good on the bleeder.

As part of my cynicism about Chinese electrical design I will point out that the 220uF input capacitor has no bleeder*.
Guess China has not reached basic EE 101 yet...

I'm not going to stay on my soap box long but I can name a half dozen quality stories about Chinese high voltage design.
The most painful was the death of a trusty HP power supply to a 5 dollar piece of Chinese crap. It was supposed to input
12 volts and turn it into a few thousand. It also put some of that few thousand back on the 12 volt line and popped my supply.

Cheers.

* It does now.

[Richard Hull]

Sorry about the rebound into your 12 volt supply. I am leary of most any switcher by the chi-coms. High voltage ones are no real gems, as a rule. Switchers are all about a snap-on of the drive voltage. Variacs are not on the most favored list for start up. These supplies work off of inrush current to get moving, as a rule. Good switchers are designed to take it and not pass dangerous over-volting to sensitive parts of the switcher circuitry.

Richard Hull