EEVblog Electronics Community Forum
Electronics => Repair => Topic started by: Christopher on March 03, 2018, 01:45:56 pm
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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 etc
Cheers for your help!!
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https://www.eevblog.com/forum/repair/field-failure-of-an-fluke-87v/msg1262071/#msg1262071 (https://www.eevblog.com/forum/repair/field-failure-of-an-fluke-87v/msg1262071/#msg1262071)
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Not the most robust meters for HV work, as joe has shown us.
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Not the most robust meters for HV work, as joe has shown us.
Yeah, but normally on HV at work we use dividers that divide 30kV+ down to a few volts so it doesn't matter too much :-)
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Not the most robust meters for HV work, as joe has shown us.
Yeah, but normally on HV at work we use dividers that divide 30kV+ down to a few volts so it doesn't matter too much :-)
Fair 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.
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Not the most robust meters for HV work, as joe has shown us.
Yeah, but normally on HV at work we use dividers that divide 30kV+ down to a few volts so it doesn't matter too much :-)
Fair 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.
Just 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 ;-)
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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.
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"And, as if on cue, here comes the sheriff".... ;D
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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.
I think it's the same as the 27 input circuit.
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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.
I think it's the same as the 27 input circuit.
Doesn't appear to be even close.
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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.
I think it's the same as the 27 input circuit.
Doesn't appear to be even close.
No 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.pdf (http://materiel-physique.ens-lyon.fr/BDD/job/BDD/Notices/N069-020.pdf)
Page 2-3 describes the input protection and page 5-14 has the schematic.
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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.
I think it's the same as the 27 input circuit.
Doesn't appear to be even close.
No 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.pdf (http://materiel-physique.ens-lyon.fr/BDD/job/BDD/Notices/N069-020.pdf)
Page 2-3 describes the input protection and page 5-14 has the schematic.
I 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.
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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....
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I 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.
With 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 varistors (https://en.tdk.eu/inf/70/db/var_11/SIOV_Leaded_StandarD.pdf) rated 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-87v (https://www.eevblog.com/forum/repair/field-failure-of-an-fluke-87v)
https://www.eevblog.com/forum/testgear/fixing-a-fluke-87v (https://www.eevblog.com/forum/testgear/fixing-a-fluke-87v)
https://www.eevblog.com/forum/repair/fluke-289-repair (https://www.eevblog.com/forum/repair/fluke-289-repair)
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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....
You 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...
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But newer Fluke multimeters have Epcos S05K575 which is a custom part. GW121 uses it too, on the schematic I found.
Very interesting that it's in the GW121............
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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 575VAC
DC voltage 785VDC
8/20usec surge 400A
Wmax 22J
Disk 5mm
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Here's some pics of another blown 87V....
I was hoping to get the mov out of it...... :-)
https://imgur.com/a/dPUAn
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I think she's dead jim.
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no hes giving everything is got captain
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How did this happen?
Here's some pics of another blown 87V....
I was hoping to get the mov out of it...... :-)
https://imgur.com/a/dPUAn
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How did this happen?
Here's some pics of another blown 87V....
I was hoping to get the mov out of it...... :-)
https://imgur.com/a/dPUAn
I would have like to have added those pictures to the intro video along with the others I had found. As I understood it, Yes I doubt there is a single 87V owner ever who has seen their meter die due to any ESD or pulse overload etc.
... Sure, if a meter is failing ESD testing or something that could potentially be common place, then that may be a cause for concern, but even the Fluke 87V has shown no sign of doing that in practice for the 13 years it's been released as the V series, apart from Joe's test.
I too would like to know more about what happened.
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How did this happen?
One of the labels on the meter reads "Do not remove - Property of Spellman High Voltage".
Hmm....