Brymen BM869 meets high voltage in real world - Page 1
Forum section: electronics / repair

author: retiredcaps
author_rank: Super Contributor
timestamp: June 01, 2016, 04:59:05 am
content: Some of you may have seen pictures of used and abused Flukes and people coming here asking for help to repair them. For example,https://www.eevblog.com/forum/repair/fluke-289-repair/I believe this might be the first Brymen BM869 that was subjected to high voltage.Here is the thread at badcaps.net, but unless you are a member, you can't see the pictures so I attached them here.http://www.badcaps.net/forum/showthread.php?t=45936There is some noise in that thread, but I thought this would be of interest to the eevblog community given its interest in Brymen meters.

author: retiredcaps
author_rank: Super Contributor
timestamp: June 01, 2016, 05:00:17 am
content: More pics.

author: TheAmmoniacal
author_rank: Unknown
timestamp: June 01, 2016, 05:59:52 am
content: Looks like the input protection did its job?

author: ivaylo
author_rank: Frequent Contributor
timestamp: June 01, 2016, 07:12:19 am
content: How high voltage (can't tell by that badcaps thread)? And in what mode was the DMM?

author: nanofrog
author_rank: Super Contributor
timestamp: June 01, 2016, 12:43:36 pm
content: Quote from: TheAmmoniacal on June 01, 2016, 05:59:52 amIndeed.The user was uninjured, based on what I read on the Badcaps thread.

author: Macbeth
author_rank: Super Contributor
timestamp: June 01, 2016, 02:43:28 pm
content: Blimey! What did he measure? A microwave transformer?Good to see that double insulation Dave goes on about doing its blast proofing job!

author: Lightages
author_rank: Unknown
timestamp: June 01, 2016, 06:33:19 pm
content: Whatever he measured it certainly had some kick to it. It looks reparable. I can help (as probably many others can) with component values if he needs them.

author: Hydrawerk
author_rank: Super Contributor
timestamp: June 01, 2016, 07:05:27 pm
content: Does this DMM turn on? Is the rotary selector OK?It's a pity that we do not know the voltage, that caused this damage. A MOT can do a serious damage at 2000V and 1Amp.http://adammunich.com/microwave-transformers/

author: Wytnucls
author_rank: Super Contributor
timestamp: June 01, 2016, 08:07:43 pm
content: I wouldn't be surprised if some of the range selector traces and contactors are damaged. That's where the high voltage usually leads to insulation failure.

author: Unknown
author_rank: Unknown
timestamp: June 01, 2016, 08:28:34 pm
content: I'd like to see forum user joeqsmith (joe smith on youtube) attempt to replicate this. I think this is a >$200 meter, so it would be a pricey experiment.

author: retiredcaps
author_rank: Super Contributor
timestamp: June 01, 2016, 09:35:20 pm
content: The thread continues at badcaps, but I copied the clean up pictures here for those without an account.

author: joeqsmith
author_rank: Super Contributor
timestamp: June 01, 2016, 11:47:28 pm
content: QuoteQuote from: steverino on June 01, 2016, 08:28:34 pmFor all I know, the OP may seen me run the BM869s and had no clue what they were watching. The BM869s survived with 6KV, 2 ohm source, 100uS FWHH and was damaged with 13KV 2 ohm source with a 50uS FWHH. Maybe after seeing this all they heard was 6KV. They knew 6KV was a lot higher than their 2KV MOT and thought that would be fine to measure directly.I like their commentQuoteOf course I really have no idea what they were doing or why they thought it would survive.With the board being burned, it may breakdown even more spectacular next time, when they are measuring the mains and they may not be so lucky!This is why I do not offer to sell or give away any of the meters I test. Why put someone at risk?One thing this person did help show is just how little energy I test the meters at. I think when I damaged the BM869s, I lost a transistor was all. No damage to the PCB or the primary protection.

author: Unknown
author_rank: Unknown
timestamp: June 02, 2016, 02:19:45 am
content: Hi Joe. Didn't realize you had tested that meter already. thanks.

author: retiredcaps
author_rank: Super Contributor
timestamp: June 02, 2016, 04:53:25 am
content: Latest over at badcaps is that with temporary 1k ohm resistors in place of the PTCs and power resistors, everything seems to check out okay. The meter lives!Would someone be kind enough to post the resistance values of the two PTCs and 3 MOVs part numbers?In addition, I know the 4 power resistors are likely 1k ohm each, but I'm unsure of the wattage and composition. I'm guessing they are 2W, but don't know if they are fusible, fireproof, metal film, etc.Thanks.

author: rsjsouza
author_rank: Super Contributor
timestamp: June 02, 2016, 10:11:28 am
content: Quote from: joeqsmith on June 01, 2016, 11:47:28 pmMe neither. Despite no parameters, such spectacular fireworks display would have ruined anything from any brand...Quote from: joeqsmith on June 01, 2016, 11:47:28 pmThat got me thinking: Joe, when you say 6kV at 2ohms for 100microsseconds you mean that your pulses carry 1800J of energy? In other words, \[E=\frac{6000^2}{2}100\mu\] That's quite a lot of oomph!

author: joeqsmith
author_rank: Super Contributor
timestamp: June 02, 2016, 11:48:56 am
content: 1800J!The IEC standards define both current and voltage waveforms. The voltage is measured into an open and the current into a short. What I describe in the videos has always been the open circuit voltage waveform. In some cases I will show the waveform with a meter connected. As long as the meter does not break down, it has little effect on the wave shape. This is why I typically monitor the waveform during the test. While I may not see or hear an event, the scope often catch it. The open circuit attack and decay are actually setup by a network that is built into the generator absorbing the energy.The current waveform I can put out is very weak compared with the standards. My goal is not to repeat what this person has done, or worse. I am just trying to find the level where they fail when tested in the same manor.The actual energy available is partly based on the size of the storage bank. Both of the high voltage generators I designed have less than 20J available to the load. I did a video using some charged capacitors discharged on a metal plate to show the levels I run at. It's not much.I'm sure some novices see these videos and some of the high voltages I test to then decide it's fine to hook their meter directly to a MOT. Some point out that the meters did not show any signs of being unsafe. Others see CAT III 600V on the meter and then comment about how they are not designed to handle anything over 600V. Then there are those who think the leads will never handle it so why expect the meters to.QuoteI was thinking, sure go buy a Fluke 289 and connect it to your MOT.Again, no idea what this person was doing or why they felt the meter would survive.Quote from: rsjsouza on June 02, 2016, 10:11:28 am

author: gnavigator1007
author_rank: Unknown
timestamp: June 02, 2016, 06:37:48 pm
content: Quote from: retiredcaps on June 02, 2016, 04:53:25 amI've been following this saga on both forums and really curious how the repair turns out. Hopefully someone comes through with those values. Got to say I'm a bit concerned this fella might end up hurting himself once he gets a functioning meter back in his hands. From what I've read he sounds like he has his personal safety too tied up with brand name rather than stopping to think if what he is about to do might kill him. Really doesn't seen to understand what the input protection is for or how it works

author: Lightages
author_rank: Unknown
timestamp: June 02, 2016, 07:56:28 pm
content: The resistors are definitely 1k, probably 2 watt. The other components that burned are not MOVs but rather PTCs. The one closest to the selector dial measures 1k000 and the other measures 1k237. The blue components, the MOVs, are marked CNR 070821K. I will try and get the actual specs and values from Brymen.

author: Lightages
author_rank: Unknown
timestamp: June 03, 2016, 05:59:10 am
content: I received an answer from Brymen:"Those components are:R1 ~ R4: 1k?/3W wire-wound resistorsPTC1, PTC2: 1.1k?/1kV PTCSPG1, SPG2: 820V Zinc Oxide VaristorSPG3: 1000V Zinc Oxide Varistor"

author: retiredcaps
author_rank: Super Contributor
timestamp: June 03, 2016, 06:13:43 am
content: I didn't expect an answer from Brymen, but I did get the exact same reply just about 60 minutes ago. I didn't see it sooner because it ended in my spam folder.HUGEto Brymen for answering my query directly!!!Thanks to Lightages for making the same query.Quote from: Lightages on June 03, 2016, 05:59:10 am

author: retiredcaps
author_rank: Super Contributor
timestamp: June 03, 2016, 06:22:06 am
content: I already know getting the 1.1k ohm/1kV PTC is going to be troublesome from doing some research for Fluke meters. While the part exists, NO ONE stocks it.YS4020http://www.mouser.com/catalog/specsheets/amphenoladvancedsensors_YS4020.pdf

author: Unknown
author_rank: Unknown
timestamp: June 03, 2016, 06:38:36 am
content: This is an upsetting story about the dangers working on high voltage equipment. It unfortunately resulted in the death of an electrician measuring high voltage with an underrated multimeter (among other violations of safety protocol).

author: rch
author_rank: Regular Contributor
timestamp: June 03, 2016, 09:50:31 am
content: Are 2.3kV motors common in industry? I vaguely thought this sort of accident only happened in power distribution plant.

author: retiredcaps
author_rank: Super Contributor
timestamp: June 03, 2016, 06:16:52 pm
content: My reply on badcaps.net regarding replacement parts ...Here is a suggested list of replacements. I tried to pick the big name/well known/reputable brands.1) Bourns 820V varistor - 17 cents each x 2 = 34 cents totalhttp://www.digikey.com/product-detail/en/bourns-inc/MOV-07D821KTR/MOV-07D821KTRCT-ND/2) Epcos 500V PTC 1.1k ohm - $2.31 each x 2 = $4.62 total (NOTE: This is a 500V PTC, not 1000V)http://www.digikey.com/product-detail/en/epcos-tdk/B59774B115A70/495-3890-ND/6520533) Vishay 1k ohm 3W resistor wirewound flameproof - 87 cents each x 4 = $3.48 totalhttp://www.digikey.com/product-detail/en/vishay-sfernice/RWM04101001JR15E1/RWMA-1.0KCT-ND/15879224) Bourns 1000V varistor - 49 cents eachhttp://www.digikey.com/product-detail/en/bourns-inc/MOV-14D102K/MOV-14D102K-ND/27982540.34 + 4.62 + 3.48 + 0.49 = $8.93 + whatever shipping (I'm guessing $4 USD for first class).Please note that while there is a 1000V PTC that 1.1k ohm, it is not available for purchase anywhere that I can find. The part number is YS4020. Datasheet athttp://www.mouser.com/ds/2/18/amphenoladvancedsensors_YS4020-492783.pdfAs such, I would consider this repaired BM869NOTa UL listed 1000V meter anymore. While the repaired meter is likely okay for normal househould mains use (120V), I would urge caution and practice good safety like wearing goggles, using hand-free probes and not working alone.I will leave it to the OP to double check part numbers and specifications, but more importantly, check the dimensions of each components. I don't have a BM869 so I cannot verify if these replacement parts are the same size or larger.Email from Brymen re components ..."Those components are:R1 ~ R4: 1k ohm/3W wire-wound resistorsPTC1, PTC2: 1.1k ohm/1kV PTCSPG1, SPG2: 820V Zinc Oxide VaristorSPG3: 1000V Zinc Oxide Varistor"

author: N2IXK
author_rank: Frequent Contributor
timestamp: June 03, 2016, 07:03:25 pm
content: Quote from: rch on June 03, 2016, 09:50:31 amYes, as are 4160V motors. Such "medium voltage" motors are common once you get into the >500HP range. This kind of gear is completely unforgiving of any mistakes or carelessness.

author: retiredcaps
author_rank: Super Contributor
timestamp: June 09, 2016, 02:16:42 am
content: OP's repair with pictures from post #57. Thanks again to Brymen and Lightages for providing the values on the input protection.http://www.badcaps.net/forum/showpost.php?p=663262&postcount=57