UT61E vs Ionizer - Page 1
Forum section: electronics / projects

author: hgg
author_rank: Frequent Contributor
timestamp: December 14, 2018, 03:52:13 pm
content: Hi,This was my first try to make a 15 stage ionizer and I had the brilliantidea to use my UT61E to debug it. A probe on the wrong componentand after a tiny flash the UT61E was zapped to oblivion...I don't careabout the meter itself as much as the work I've done for all the upgradesit has. So any help would be much appreciated!The Killer :The "new" selection modes after the zapping :I've tried to see if there was anything obvious on the board but there is not.If you look at the photo below diodesD5 & D6 measure dead shortin either directionand the double diodeD4 has a voltage drop of 0.1Vin either direction as well.(meter was in off position).Is this normal? Looks like that these diodes are dead. What do you think?The meter works correctly only in capacitance and Amperes mode.I hope there was no damage on the main chip ES51922.Can you please help me track down the problem?Thank you!Schematic :

author: 001
author_rank: Super Contributor
timestamp: December 14, 2018, 04:51:21 pm
content: Nice photosCheck Q5&Q6 and MOVsUse 990M resistor serial with Your meter next time and multiply readings x10

author: Wolfgang
author_rank: Super Contributor
timestamp: December 14, 2018, 04:55:43 pm
content: I would say its time to say farewell. R.I.P, Uni-T. Maybe a 87V next time

author: joeqsmith
author_rank: Super Contributor
timestamp: December 14, 2018, 06:05:10 pm
content: There isn't much to these meters. The fact that the FC pins are no longer working tells me the main IC has a problem. It may be difficult to source a replacement.I've damaged a few of these. They are not the most robust of meters. Actually, pretty low on the scale compared with the others I have looked at. Still, hard to say if a top of the line meter would have survived the same mistake.

author: hgg
author_rank: Frequent Contributor
timestamp: December 14, 2018, 06:18:31 pm
content: Indeed they are not, although the applied voltage was many KV.D5 and D6 are actually ok. There is a 9 Ohms resistor across.I removed the switching double diode D4 and one of the internaldiodes was shorted. Maybe there is a chance that the IC survived.I will order a replacement diode and see what happens.

author: hgg
author_rank: Frequent Contributor
timestamp: December 14, 2018, 06:57:45 pm
content: I will have the replacement diode next Tuesday.The meter works fine in Hz, A and Capacitance modes.D4 controls the FC1 & FC4 lines and if you have a look at the table below you can seethat these are the modes when FC1 & FC4 are zero. Would the above behavior benormal when one of the diodes inside D4 is shorted?

author: joeqsmith
author_rank: Super Contributor
timestamp: December 14, 2018, 07:38:42 pm
content: You could try a couple of switching diodes easy enough just to see.

author: hgg
author_rank: Frequent Contributor
timestamp: December 14, 2018, 07:41:02 pm
content: I'll give it a try.

author: stj
author_rank: Super Contributor
timestamp: December 14, 2018, 07:48:52 pm
content: Quote from: Wolfgang on December 14, 2018, 04:55:43 pmi knew some fanboy would say that!next you will say the fluke would have given the correct voltage, even in "ohms" range with the probes in the current-jacks!

author: cdev
author_rank: Super Contributor
timestamp: December 14, 2018, 07:59:11 pm
content: Somebody else did exactly the same thing - as I remember reading it, some years ago..posted here in some older thread.Quote from: hgg on December 14, 2018, 03:52:13 pm

author: hgg
author_rank: Frequent Contributor
timestamp: December 14, 2018, 08:04:32 pm
content: Do you remember what happened?Dead UT61E ?

author: cdev
author_rank: Super Contributor
timestamp: December 14, 2018, 08:32:27 pm
content: No but it was here that I saw it and I suspect the word 'ionizer' was also used. Or something close to it.

author: nickeevblog10
author_rank: Contributor
timestamp: December 14, 2018, 09:12:42 pm
content: Just out of interest and I do like posting this experience with the UNI-T 61E, after dismantling and reassembling then using the meter i was getting unusual readings. I found the ribbon around the readout LCD? was not wrapped perfectly around the edges of all the four sides of the display. It did take a bit of doing but eventually getting the ribbon back into place and readouts became normal. Do check this, for me a newbie this was great news.The other problem I had with digital multi meter readers is using a meter that did not, not sure how to describe this, would not OL automatically but the UNI-T 61E does OL automatically. I did not need the UNI-T 61E (lol) but i like it with no mods.

author: Wolfgang
author_rank: Super Contributor
timestamp: December 14, 2018, 09:14:09 pm
content: In fact I have UNI-Ts *and* Flukes. While I had to fix the UNI-Ts several times, the only think I ever changed on a Fluke was a fuse.

author: cdev
author_rank: Super Contributor
timestamp: December 14, 2018, 10:54:45 pm
content: I really like my UT-61E so I think that if I broke it I would try to exhaust all the possibilities to see if it was fixable and fix it if possible, before tossing it out.I make it a practice of trying to fix things that break and even if I am not successful, I always learn something.

author: Wolfgang
author_rank: Super Contributor
timestamp: December 14, 2018, 11:02:41 pm
content: Quote from: stj on December 14, 2018, 07:48:52 pmWith a Fluke, its worth a try.

author: Electro Detective
author_rank: Super Contributor
timestamp: December 14, 2018, 11:07:06 pm
content: LOL, here we go, the gents are at it again...Sad news there hggwhat kind of zappage can one expect from an ionizer circuit?Fanboy BS aside, as a Fluke owner user I'm confident the 87V would have got (eventually) zapped just as well as the UT61E,but with a replacement 10x price tag for the adventureGood luck with the repair/s or if no go, you'll have spare parts on hand if you buy another UT61E.. or two..Quote from: 001 on December 14, 2018, 04:51:21 pmmultiply x10 or x100 ?Good advice, I use a 90M chain, next one will be a 990M 'upgrade' to be sure

author: NiHaoMike
author_rank: Super Contributor
timestamp: December 15, 2018, 01:46:04 am
content: Quote from: joeqsmith on December 14, 2018, 06:05:10 pmIt's just 10kV with little energy behind it, basically ESD. Didn't several low cost Flukes survive 15kV with a very substantial amount of energy behind it?

author: 001
author_rank: Super Contributor
timestamp: December 15, 2018, 03:27:29 am
content: Quote from: blueskull on December 15, 2018, 01:58:45 amIs it Joke?1000V CAT IV is rated for 6kV impulse

author: joeqsmith
author_rank: Super Contributor
timestamp: December 15, 2018, 03:45:02 am
content: Quote from: NiHaoMike on December 15, 2018, 01:46:04 amI have lost a fair number of UNI-T meters to a piezo gas grill ignitor. After so many UNI-T fan boys complained about the grill starter, I decided they were right and built the gun I now use. Hard to say what the OP's 61E was exposed to. It could very well be worse than the standard calls for. I can tell you that I can zap myself with the grill starter and on a pain scale of 1-10, I give it a 1. The gun I made is maybe a 2. When I tested the Fluke T6 with my hand in the circuit, I give that a 4.The first 10 minutes of this video I talk about ESD.https://youtu.be/1kYcY2ogmqoTesting the T6 with my hand because I heard on the internet it would kill me.....https://youtu.be/k8hhtTtWfVc?t=2634

author: Nusa
author_rank: Super Contributor
timestamp: December 15, 2018, 07:01:57 am
content: Quote from: 001 on December 15, 2018, 03:27:29 amA Fluke 87-III is only a CAT III meter, last time I checked.Also what blueskull said.

author: 001
author_rank: Super Contributor
timestamp: December 15, 2018, 08:32:32 am
content: OkHow to live now?

author: hgg
author_rank: Frequent Contributor
timestamp: December 15, 2018, 08:39:10 am
content: I've connected 2 diodes together in place of the double package.It looks like the IC internal pull up resistors are messed up.I've also connected two pots from ground to FC1 and FC4 andafter some fiddling I've manage to show all the selection rangesin the correct order but Volts mVolts and Ohms do not workproperly. The pots were at approximately 48Ohms.Any ideas? Is it dead?

author: hgg
author_rank: Frequent Contributor
timestamp: December 15, 2018, 09:10:52 am
content: Zero is -3.0V and One is floating around -100.0mVIn all modes except mV, Hz and Amps FC4 and FC1 lines show -2.5V or -1.5V instead of -3.0VHow can I find the values of the pull up resistors that the IC needs?I am preparing the garbage bin with a new plastic bag...

author: stj
author_rank: Super Contributor
timestamp: December 15, 2018, 02:22:44 pm
content: all the resistors have the values on them - just check everything.btw,on another forum there was a guy with a fence-charger.he "tested" it with a fluke87 and killed it - no surprise really.if you can kick a cow over a mile from the device via damp soil and a fence the energy must be pretty nasty.what was funny, he then "tested" it with a uni-t mini meter and it displayed 3KV!!!!i dont know if that was the true voltage but it didnt kill the meter

author: 001
author_rank: Super Contributor
timestamp: December 15, 2018, 02:30:28 pm
content: Quote from: stj on December 15, 2018, 02:22:44 pmOnce I checked TV tube with unit like Harbor FreightAnd it says 1300 DC without damage

author: hgg
author_rank: Frequent Contributor
timestamp: December 15, 2018, 02:35:14 pm
content: QuoteI thought these resistors were internal to the IC.Which ones are you referring to?

author: stj
author_rank: Super Contributor
timestamp: December 15, 2018, 03:32:22 pm
content: i'm saying - CHECK EVERYTHING.

author: joeqsmith
author_rank: Super Contributor
timestamp: December 15, 2018, 04:01:20 pm
content: Quote from: hgg on December 15, 2018, 02:35:14 pmThey are. Your 48 ohm resistors is another tell tail that the control IC has seen better days.

author: hgg
author_rank: Frequent Contributor
timestamp: December 15, 2018, 04:12:23 pm
content: Hmmm. The chances of reviving the meter are going down by the minute...Its also very difficult to source this IC. It looks like that although only onediode (from the two in the switching package) was zapped, both FC1 & FC4were damaged inside the IC. After installing external resistors to ground,the modes are ok, but mV, V and Ohms do not work. V mode flashes like itchanges every half a second from one mode back to V, mV does the samebut extremely fast and displays OL and Ohms does not measure anything.

author: joeqsmith
author_rank: Super Contributor
timestamp: December 15, 2018, 04:30:44 pm
content: There have been people on these forums that have spent a lot of time trying to revive a low cost meter like this.I typically test the meters to failure and will have a quick glance to see if they can be repaired. That is one of the things I see with the better class of meters. They have enough protection that normally the controller ICs are not damaged and I am able to repair them. The lower class of meters, it's rare I can do anything besides recycling them.

author: cdev
author_rank: Super Contributor
timestamp: December 15, 2018, 06:42:24 pm
content: What can be done to preemptively mod the meter so it wont be as susceptible to damage, and does it reduce its accuracy?Backlight- not so important to me - durability- important to me.

author: joeqsmith
author_rank: Super Contributor
timestamp: December 15, 2018, 07:25:02 pm
content: The best thing you could do is buy a better class of meter to start with if you are playing with HV's like the OP is. The worst thing you could do is to modify a safety device in any way.That said, it may be possible to use something like I show in the following video.https://youtu.be/bj_YndfA4Qs

author: MosherIV
author_rank: Super Contributor
timestamp: December 15, 2018, 07:50:13 pm
content: QuoteAdd the MOVs, they are marked on the PCB but have not been installed. Not sure if it will totally protect the meter. They should clamp the input voltage in case of an over volt.I have done it to my ut61e. The only measurement it have affected is the capacitance.Joe has done some tests. The MOVs he tested did not give total protection to the meter. It did survive some over voltage if I remember correctly.

author: joeqsmith
author_rank: Super Contributor
timestamp: December 15, 2018, 08:57:26 pm
content: You are correct that adding the MOVs would have never saved my meter from the piezo gas grill ignitor. The nature of poor UNI-T designs I'm afraid. I made a few videos showing the problems and how I addressed them. As you suggested, I did run several transient tests after making the changes to demonstrate them.Just to be clear, while it was mentioned in that video and others, when you start dealing with waveforms in the ns with rise times in the ps there is a lot that will come into play. Just sprinkling parts onto a board may not prove to be effective.

author: hgg
author_rank: Frequent Contributor
timestamp: December 16, 2018, 07:33:01 am
content: In the case of high voltage low current, the UT61E is vulnerable at is FC linesthat connect directly to the main IC.The board has test points for each of the FC lines.What about if we use something like the following to each of the line, and especially before theswitching diode D4 ? They are very fast and go up to 8kV.https://www.onsemi.com/pub/Collateral/ESD7951S-D.PDF

author: hgg
author_rank: Frequent Contributor
timestamp: May 01, 2019, 02:09:42 pm
content: Just an update.Today I found the courage to try to repair the UT61E...After a long and nerve wracking soldering session, I've removed the main IC and replaced it with a new one.The UT-61E came back from the dead and works perfectly fine!I used one full Rossmann unit of flux for soldering.. and while it was soldered fine, its a PITA to cleanthe flux afterwards from that type of package. An ultrasonic cleaner will be the next purchase I think.It was indeed the main IC that got zapped. No clamping diodes, no other component, just the IC.Its FC lines have no protection whatsoever from electrostatic discharges and I think that this waswhat killed it. I will order a 4 channel ESD diode IC to clamp all the FC lines.I've also replaced the voltage calibration pot with a 2K Bourns. A 1K would have been a better choicesince only two legs are connected and the resistance when calibrated is around 565Ω.I've also cleaned and greased the rotary switch contacts and its back in service as new!I know, its a cheap meter but I am sure that everybody knows the feeling when you bring backfrom the dead a piece of electronics equipment, especially if you have been using it a lot and alsomade a lot of mods. Cheap stuff and things that do not work optimally is the best way to learn!Thanks for the help.

author: joeqsmith
author_rank: Super Contributor
timestamp: May 01, 2019, 02:33:02 pm
content: If you read the datasheet, there is a reason they do not clamp it. Too much leakage. I did show in the video how I addressed this.

author: hgg
author_rank: Frequent Contributor
timestamp: May 01, 2019, 02:40:06 pm
content: The following is advertised for low leakage : (100nA)https://www.onsemi.com/pub/Collateral/NUP4004M5-D.PDFHave you tried something like that?

author: joeqsmith
author_rank: Super Contributor
timestamp: May 01, 2019, 03:15:15 pm
content: Quote from: hgg on May 01, 2019, 02:40:06 pmEasy enough to calculate the error it will cause and see if that's acceptable to you.No, I only tried what I showed when I made that video.

author: stj
author_rank: Super Contributor
timestamp: May 02, 2019, 09:13:41 am
content: so how much did the chip cost?

author: hgg
author_rank: Frequent Contributor
timestamp: May 02, 2019, 11:47:46 am
content: It was kindly provided and shipped free of charge from CyrusTek.1000 Thanks to CyrusTek

author: stj
author_rank: Super Contributor
timestamp: May 02, 2019, 06:14:04 pm
content: nice, they should open a store on AE.