Making do with what you got/ Fluke 332D failed main transformer rescue mission - Page 1
Forum section: electronics / general

author: View[+]Finder
author_rank: Unknown
timestamp: January 24, 2021, 08:51:59 pm
content: Hi All,ViewFinder here.I have a Fluke 332D that was working fine until--for no discernible reason--the main transformer shorted one leg of the 44VAC supply. That cascaded into a failure of the board that uses the 44V. And so it sat while I looked for a replacement transformer . . . for over a year.Rather than dispose of it, I thought it might be salvageable (not by selling parts, please) so I looked into what the transformer provided. Aside from the HV (more on that later), the rest of the AC voltages can be had from modern transformers from the likes of BEL and sold on Mouser.Short story: I got it working again.Questions welcome.Regards,Donal

author: TiN
author_rank: Super Contributor
timestamp: January 24, 2021, 08:56:16 pm
content: If we talking about these shielded transformers, I doubt any COTS replacements from Mouser will be a adequate replacement. I've got few years ago forPSU projectthat didn't happen."If anyone wants the longer story and pictures, hit the "Thank" button and I'll post here."I'd suggest just go ahead and post details. Keep it simple, thanks.

author: View[+]Finder
author_rank: Unknown
timestamp: January 24, 2021, 11:10:57 pm
content: Hello Illya,Those, yes. The multi-voltage one failed. No surprise, they are not "an adequate replacement' for the Fluke. They are, however very much in the spirit of "making do with what you got."The 332D was dead. Once I decided that there was value in the remains--mostly based on posts about the quality of the "front-end"--I gutted the entire back section. (Anyone who wants the working HV transformer may have it for the cost of postage. Seriously: free.) The realization that, aside from the 1000V capability (a big deal for some, true), the 332D can power-up on just three AC voltages: 88V CT (so OK 4 voltages), 32VAC and 22VAC. All the rectification and filtering is on the individual boards. I did this transformer-transplant surgery mainly to see if the remaining boards were serviceable, I didn't want to add them to electronics waste and selling them untested is not my thing. Ok, and also to see if it could be done. And for the fun it.I plan to post the whole story here, with photos and data, much of it will make some people laugh and some will cringe. Or both.Right now my 332D is still a work-in-progress, but capable of supplying current of 60mA (yes, of questionable quality) at anywhere from zero to 100VDC by setting the knobs on the front panel. Without buzzing and with far less input from the mains power.Best regard,Donal

author: TiN
author_rank: Super Contributor
timestamp: January 24, 2021, 11:35:11 pm
content: Don't worry about people that much and post away. The more documentation, the better.From threads in the past, many hobby labs still have Fluke 33* beasts and use them, so will be useful for somebody who looking for budget calibrator, for sure.

author: View[+]Finder
author_rank: Unknown
timestamp: January 27, 2021, 09:05:24 pm
content: Attached is a photo of my Fluke 332D on the operating table being checked for the correct function of the 'transformer-transplant'. The largest is an 88V center-tap for the +44VAC and -44VAC to the Current Limiter board; the middle one is a 34VAC (original tap on the Fluke was 32V) for the Aux Power Supply board 25VDC supply and the small one is a 22VAC for the Aux PS -15VDC supply. Those are all that are needed to power up the 332D.Removed in good condition was the Fluke transformer for 1100VDC and the main power motherboard that hosted the Pre-regulator board and the Series Pass Element. The latter can be seen in its potential new location.In this rebuild there is no provision for the 1000 volt capability. This means that the primary mission of the main board and pre regulator--safe generation of the HV supply--has been canceled. The Series Pass Element has its old job, but under new management.More to come . . .

author: View[+]Finder
author_rank: Unknown
timestamp: January 28, 2021, 12:14:11 am
content: SAFETY BRIEFING:One benefit of not having the HV transformers in the 333/335 is that the risk of serious electroshock is minimized. Some years ago, I was adjusting HV on my 332D set at 800VDC with the case on, however the panel covering the fiberglass adjustment area was off. A brief contact with some metal gave me a shock and resultant burn on a tiny area of one finger. It took over a week to heal.With no HV on board, there is still the 44VAC and its evil twin, -44VAC. Getting across them will give you an 88volt shock and that could be deadly. Be careful.There are two high voltage current sources that remain to be replaced in the 332D: the Series Pass Element will need 150VDC for operating voltage for the series of transistors that are responsible for voltage regulation. In my 332, this voltage is supplied by a power supply designed for commercial LED lighting. This is no 'wall-wart'. It is an aluminum sealed box that puts out a regulated amp or so at 150VDC (adjustable). In the original configuration, it came from the HV transformer and was rectified on the Series Pass Element boar. Giving a rectifier DC works just fine in this case, although one could consider a redesign, I suppose.Finally, there must be a source of DC for the front end to provide out to whatever is plugged into it. This is what the Pre-regulator and some associated components on the main board were tasked with generating and regulating. Being cautious and feeling my way through schematics while re-reading the Theory of Operation about a hundred times, my first attempt at this source was a bench power supply. When that worked out ok, I wanted to be able to close up the case, so I installed a couple of 6S LiPo batteries in series, giving the 332 the potential to output around 60mA at 50VDC.I've left out a description of hours of peering at and through the backplane to trace out all the necessary connections, finding an actual wiring layout for the 332 (hint: its for the 335) and worrying over what to remove and what must be left in place. I even created an iCircuit model of the 332 once I figured out that it is essentially a very large OP AMP with a precision voltage divider on the sense side of the negative input.Photo attached of the 332 giving a piggy-back ride to a couple of voltmeter friends. The black item is one of the 6S LiPo batteries riding shotgun this time. I'm sure there must be a number of 33d's that produce what is dialed in, this is not yet one of that number. . .

author: MadTux
author_rank: Frequent Contributor
timestamp: January 29, 2021, 02:18:38 am
content: Fluke 332/335/5440 with HV capabilities neutered would be quite useless for me.These things are nice HV power supplies, like for testing switching power supplies or variable frequency drives and other things that usually operate from rectified 3phase 380V and need like 580VDC to work.

author: TiN
author_rank: Super Contributor
timestamp: January 29, 2021, 02:52:50 am
content: Hmm, 5440 as HV supply for VFD or 3phase device (with 25mA of current compliance capability). Not everyday I hear this

author: MadTux
author_rank: Frequent Contributor
timestamp: January 29, 2021, 12:14:15 pm
content: Couple of welders that I repaired (or tried to) have on (PCB) board SMPS that take rectified 3phase 380V, ie 580VDC as supply voltage to make like +/-15V and 5V.So if you want to test these outside of the welder with safe currents so not everything gets toasted with like 63A before fuse blows, you need a 580VDC PSU.Fluke 332 or 5440B was very useful for that, because I don't have to buy another HV PSU. And those 35W that a 5440B supplies at 580V is usually more than enough for electronics.Pics of a galvanic power supply board that I had for repairs recently. That black brick on the left with the 2 transistors in front is SMPS that takes 580V. So to check if I successfully removed the short and all linear regulators are still fine, I needed something to power it......

author: View[+]Finder
author_rank: Unknown
timestamp: January 30, 2021, 12:10:48 am
content: The Fluke 332D is a voltage standard, not a power supply. Mine was working fine and then it wasn't. A failure of either of the two transformers is fatal and that is a long way past "neutered." Now mine is 'ok' up to over 100V as a reference, the next stage of recovery will be to turn "OK" into something better.In addition to the 332D, I have access to a Keithley 337 SMU, an HP 3KV power supply and an ancient Fluke 10KV power supply. I forget the exact specs, but I don't think any of the three HVPS's will output more then 100mA. There are ways to get HV and amps as the fans of Tesla coils and Jacobs Ladders will attest, and do it for a lot less than the cost of a 332D on eBay. For your testing at the >500V level, how many amps do you need? More important, at what level of precision? There are ways . . .If all you need to do is test the circuit--and are not going to strike an arc or otherwise short the output--why not test at a lower voltage? Wouldn't that just translate into a lower output? Or if your repair job was unsuccessful, at least a more manageable fire? I assume the welder had/has a 3-phase rectifier and that it still works, so there's a source of 580VDC.