What to do with a 4000 V power supply (plus mini tear-down) - Page 1
Forum section: electronics / testgear

author: SharpEars
author_rank: Unknown
timestamp: November 22, 2015, 03:53:41 am
content: What to do with a 4000 power supply? That's the question I've been asked countless times since I got it.Well, I've grown tired of having to think of an answer to that question and here is what I am going to use it for, once and for all:Click on the images for a screenfull...That's right 4 kV going right into a red LED. Just kidding of course, it is being current limited (CC mode) to a nice warm and cuddly 10 mA. If I really put 4kV into that LED it would probably blow like no LED has been seen blowing before.For anyone interested in what goes on inside one of these beasties, here is the first pic on the net of the guts of this particular model (electronics porn warning):Yes, everything is big in Texas (and 4 kV power supplies). The mains transformer is the little one on the left side with the 33k resistor across it. You can probably guess what the mother of all power supply transformers in the center does (covered with poured wax too, with little waxcicles that formed on the bottom of it from the pour).There is a bit of a bodge in there, because I had to replace a 200k 1% (low ppm?) resistor that had gone bad and was screwing up the voltage setting of the hundreds dial:This is a temporary solution and those aren't just crappy Chinese 1% resistors I soldered in there, they're actually hand picked low ppm resistors (0.1%, +/-15 ppm) that measure almost exactly 200k together (200,005 ohms if my meter is spot on). Unfortunately, together they're only spec'ed at 0.25 W each for a combined 0.5 W load handling ability across the two of them, so I need to replace them with something more substantial. I believe the correct power rating on the rest of the resistors is 1 W, so the search won't be too bad (and the bodge will survive at least for the short term) - I hate entering unobtainium territory with these old supplies. When used properly with a fixed load, there is only about 25 mW flowing through each of them, but I do intend to replace them with the correct part once I place my next order through DigiKey.Anyways enough of my rant and I hope you've enjoyed this post.Update:You came in here expecting more (i.e., sparks flying)? Well, here is what 3.2 kV flying through an air gap of about 1/16" (1.5 mm) of air looks like. It took me about a hundred picture attempts at high speed to capture it well:

author: Cubdriver
author_rank: Unknown
timestamp: November 22, 2015, 06:06:19 am
content: Very cool. I have its 1kV cousin in my pile-o-stuff-to-be-gone-through; bought it cheap on eBuy a few months ago intending to ultimately use it to re-form electrolytics for tube gear - CC/CV settings with a voltage capability higher than anything I'd encounter as a cap would let it run (relatively) unattended - set voltage and current limits, connect cap, turn on and watch things out of the corner of my eye. It's a PITA doing them on my Sprague TO-4 as I have to keep checking the leakage current and bumping up the voltage as the oxide layer builds and the current drops off.It's nice to see pics of the innards; I haven't yet opened mine up.-Pat

author: crispy_tofu
author_rank: Super Contributor
timestamp: November 22, 2015, 09:59:33 am
content: Thanks for sharing, really cool!Quote from: SharpEars on November 22, 2015, 03:53:41 amI would love to see that, entirely new level compared to connecting an LED straight to the mains.

author: SeanB
author_rank: Super Contributor
timestamp: November 22, 2015, 11:39:38 am
content: Try a glass fluorescent lamp starter. Never was able to find any part aside from the remains of the base with the 2 blackened pins in the bakelite. The dog was skittish the rest of the day as well, after he came back from the bottom of the garden.

author: jeroen79
author_rank: Frequent Contributor
timestamp: November 22, 2015, 12:31:54 pm
content: Topic title is a bit misleading for the members in countries where the , is the decimal separator

author: SharpEars
author_rank: Unknown
timestamp: November 22, 2015, 01:54:29 pm
content: Quote from: jeroen79 on November 22, 2015, 12:31:54 pmDigit grouping comma purged from title...

author: moya034
author_rank: Regular Contributor
timestamp: November 22, 2015, 03:51:47 pm
content: Quote from: SharpEars on November 22, 2015, 03:53:41 amEasy question! The answer is clear... Plate supply for an RF amplifier in the kW range under development.

author: SharpEars
author_rank: Unknown
timestamp: November 22, 2015, 10:19:25 pm
content: Quote from: moya034 on November 22, 2015, 03:51:47 pmI was hoping to find a more practical use case to silence the critics...

author: moya034
author_rank: Regular Contributor
timestamp: November 22, 2015, 10:27:41 pm
content: Well if you are ham radio operator like me who likes building stuff I'd say that's practicalHow about testing CRT's and other HV tubes?Edit: Also don't forget laser power supply!

author: SharpEars
author_rank: Unknown
timestamp: November 22, 2015, 10:32:11 pm
content: Quote from: moya034 on November 22, 2015, 10:27:41 pm"Interesting" lasers require far more than 50 mA, though. This supplies maxes out at that current.

author: moya034
author_rank: Regular Contributor
timestamp: November 22, 2015, 10:38:31 pm
content: How about a leakage tester? Could also use a voltage cascade circuit to get even higher voltages.

author: SharpEars
author_rank: Unknown
timestamp: November 23, 2015, 12:32:48 am
content: The main post has been updated with a real high-voltage demo so as not to disappoint...

author: Vgkid
author_rank: Super Contributor
timestamp: November 23, 2015, 03:24:35 am
content: I did not see the 200k resistor in the parts list for the thumbwheel assembly, but it might be cheaper to bodge in 2 100k(.50W) resistors in series(as you have done) if you want to stay with the 1W voltage rating. It is cheaper than a single 1W 1% resistors.

author: SharpEars
author_rank: Unknown
timestamp: November 23, 2015, 02:40:19 pm
content: Quote from: Vgkid on November 23, 2015, 03:24:35 amThe reason you don't see a 200k resistor in the parts list is because they screwed it up. There are no 200 ohm resistors (those are supposed to be 200k) on the thumbwheel assembly.

author: saturation
author_rank: Super Contributor
timestamp: November 23, 2015, 04:19:03 pm
content: Given so much counterfeit is about, I use mine for kV testing of components.

author: SharpEars
author_rank: Unknown
timestamp: November 23, 2015, 05:30:03 pm
content: Quote from: saturation on November 23, 2015, 04:19:03 pmThey're all counterfeit until proven otherwise, especially if bought on eBay.

author: Terry Lingle
author_rank: Contributor
timestamp: November 24, 2015, 01:03:08 am
content: Looks like that would build a good mouse trap.Self cleaning just an ash grate to deal with . Proper bait placement would make it a low bait use model as wel.l

author: SharpEars
author_rank: Unknown
timestamp: November 24, 2015, 03:35:58 am
content: Quote from: Terry Lingle on November 24, 2015, 01:03:08 amCan I use a 0.1 uF ceramic disc capacitor as fake cheese? Charge it to a nice and cozy 4 kV and when the mouse bites it, well you get the picture...

author: iampoor
author_rank: Frequent Contributor
timestamp: November 24, 2015, 05:27:51 am
content: Quote from: SharpEars on November 24, 2015, 03:35:58 amIf you di some wood burning with it, I would be interested in knowing if using a variable supply is worth it or not!