Fluke 87V - Page 1
Forum section: electronics / repair

author: Christopher
author_rank: Frequent Contributor
timestamp: March 03, 2018, 01:45:56 pm
content: So someone at work (not me!) blew up a Fluke 87V by putting too many DC Volts into it. (we design HV power supplies)The DMM was new 9 months ago, too!I've been aloud to take it as scrap ;-)Symptoms: low voltage reading. Put 1V in, read 0.7V.Failure mode: 3 MOVs in series, one is short.Fix: remove MOVs and tried all (<60V) ranges again. All OK.So I am looking for some replacement MOVs, I have not much information but have searched already with not much luck.Marking "K575", EPCOS I think. See pictures.Only requirement is I must be able to get small QTYs, and be from somewhere easy like Farnell, RS, eBay etcCheers for your help!!

author: saturation
author_rank: Super Contributor
timestamp: March 03, 2018, 05:21:30 pm
content: https://www.eevblog.com/forum/repair/field-failure-of-an-fluke-87v/msg1262071/#msg1262071

author: don.r
author_rank: Frequent Contributor
timestamp: March 03, 2018, 05:39:42 pm
content: Not the most robust meters for HV work, as joe has shown us.

author: Christopher
author_rank: Frequent Contributor
timestamp: March 03, 2018, 08:21:08 pm
content: Quote from: don.r on March 03, 2018, 05:39:42 pmYeah, but normally on HV at work we use dividers that divide 30kV+ down to a few volts so it doesn't matter too much :-)

author: don.r
author_rank: Frequent Contributor
timestamp: March 03, 2018, 08:33:30 pm
content: Quote from: Christopher on March 03, 2018, 08:21:08 pmFair enough. TBH, I don't think any DMM would survive 30kV. At least the MOVs saved the rest of the meter. I think joe showed the 87V failing at a few kV which is dismal but not unexpected for such an antiquated design.

author: Christopher
author_rank: Frequent Contributor
timestamp: March 03, 2018, 09:05:41 pm
content: Quote from: don.r on March 03, 2018, 08:33:30 pmJust to confirm, I think this was only a bit above a kV, just the case someone winding the wick up a bit too high by mistake....But hey, no real damage done, just a couple of MOVs and I'm now a multimeter up. Hell i may even buy the guy a couple of beers ;-)

author: joeqsmith
author_rank: Super Contributor
timestamp: March 04, 2018, 01:48:32 am
content: Too funny, I am right now in the process of tracing out the front end of an 87V.Just an FYI, there are four diodes located next to the MOVs. I test at fairly low energy levels and with all the series resistance, have yet to damaged a MOV with my testing. With the 87V it's been the high speed clamps that are made up of these diodes. You may want to have a quick look. Good luck. Hope you are able to repair it.

author: don.r
author_rank: Frequent Contributor
timestamp: March 04, 2018, 02:02:16 am
content: "And, as if on cue, here comes the sheriff"....

author: floobydust
author_rank: Super Contributor
timestamp: March 04, 2018, 02:43:42 am
content: Quote from: joeqsmith on March 04, 2018, 01:48:32 amI think it's the same as the 27 input circuit.

author: joeqsmith
author_rank: Super Contributor
timestamp: March 04, 2018, 02:52:11 am
content: Quote from: floobydust on March 04, 2018, 02:43:42 amDoesn't appear to be even close.

author: tooki
author_rank: Super Contributor
timestamp: March 04, 2018, 02:55:32 pm
content: Quote from: joeqsmith on March 04, 2018, 02:52:11 amNo idea how close it is, but here's the service manual for the original 87:http://materiel-physique.ens-lyon.fr/BDD/job/BDD/Notices/N069-020.pdfPage 2-3 describes the input protection and page 5-14 has the schematic.

author: joeqsmith
author_rank: Super Contributor
timestamp: March 04, 2018, 03:59:27 pm
content: Quote from: tooki on March 04, 2018, 02:55:32 pmI posted a video yesterday where I had traced out parts of the front end of the 87V. If you look at 5-14 (showing the front end of the 87), note CR8 in series with CR7 then returning to the common through Q1. It's similar. They are using the BAV99 rather than the BAV199. Maybe they were having too many returns and wanted to beef it up a bit. The 87V I suspect used a TVS rather than Q1 for the return. They also leverage the dual pack diodes in the 87V. The 87 used a combination of a GDT and MOVs. The 87V looks like it will clamp at a lower voltage. Again, maybe an attempt to make the design more robust.

author: Christopher
author_rank: Frequent Contributor
timestamp: March 04, 2018, 05:46:41 pm
content: awesome joe !i'd be interested in seeing that frontend cct. We use a lot of Keithly 2002 and 2100s and they all seem to blow up after overloads on the mA jack and sometimes the V jack. this is good for me as they are normally and easy repair.Still not sourced a replacement MOV. anything i should take into account? I think they are 575V MOVs, just really tiny....

author: floobydust
author_rank: Super Contributor
timestamp: March 04, 2018, 11:09:01 pm
content: Quote from: joeqsmith on March 04, 2018, 03:59:27 pmWith the protection circuit, no component changes etc. as it invalidates your 61010 approval. Fluke would've beefed it up and re-tested, as required for that standard.No one has found that exact MOV used in Fluke multimeters?Mouser lists it but only with a recalibration service.From old service manuals: Fluke 706838 "Varistor 430V 1mA +/-10%; V264LAX1398"Epcos/TDK varistorsrated 430VDC 1mA are 275VAC, which is close to 264V.But newer Fluke multimeters have Epcos S05K575 which is a custom part. GW121 uses it too, on the schematic I found.More people looking for the part:https://www.eevblog.com/forum/repair/field-failure-of-an-fluke-87vhttps://www.eevblog.com/forum/testgear/fixing-a-fluke-87vhttps://www.eevblog.com/forum/repair/fluke-289-repair

author: joeqsmith
author_rank: Super Contributor
timestamp: March 05, 2018, 12:01:47 am
content: Quote from: Christopher on March 04, 2018, 05:46:41 pmYou can skip to the end of that video to see what bits I traced out on the circuit. Any idea what levels it was exposed to? Or won't the person who did it say? lol. I swear, it was just sitting on the table and it died...

author: Christopher
author_rank: Frequent Contributor
timestamp: March 05, 2018, 08:39:50 pm
content: Quote from: floobydust on March 04, 2018, 11:09:01 pmVery interesting that it's in the GW121............

author: floobydust
author_rank: Super Contributor
timestamp: March 06, 2018, 12:25:56 am
content: Some parts designed to just pass regulatory safety tests, to keep size down. Fluke uses it in many of their multimeters.No Epcos standard offerings are that small (5mm) at that high voltage; choice is 550VAC/10mm or 460VAC/5mm.S05K575 specs:AC voltage 575VACDC voltage 785VDC8/20usec surge 400AWmax 22JDisk 5mm

author: Christopher
author_rank: Frequent Contributor
timestamp: March 15, 2018, 08:50:12 pm
content: Here's some pics of another blown 87V....I was hoping to get the mov out of it...... :-)https://imgur.com/a/dPUAn

author: imidis
author_rank: Frequent Contributor
timestamp: March 15, 2018, 08:57:14 pm
content: I think she's dead jim.

author: coromonadalix
author_rank: Super Contributor
timestamp: March 16, 2018, 10:34:46 pm
content: no hes giving everything is got captain

author: saturation
author_rank: Super Contributor
timestamp: March 18, 2018, 05:05:26 pm
content: How did this happen?Quote from: Christopher on March 15, 2018, 08:50:12 pm

author: joeqsmith
author_rank: Super Contributor
timestamp: March 18, 2018, 05:27:43 pm
content: Quote from: saturation on March 18, 2018, 05:05:26 pmI would have like to have added those pictures to the intro video along with the others I had found. As I understood it,Quote...QuoteI too would like to know more about what happened.

author: giosif
author_rank: Frequent Contributor
timestamp: March 18, 2018, 09:44:15 pm
content: Quote from: saturation on March 18, 2018, 05:05:26 pmOne of the labels on the meter reads "Do not remove - Property of Spellman High Voltage".Hmm....