EEVblog Electronics Community Forum
Products => Test Equipment => Topic started by: DaleElliott on October 09, 2016, 04:33:51 am
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I would appreciate some help in identifying the burned components in the picture. I think the resistor is a 1K ohm 2W but I am not sure what the other components are. They may be caps or MOVs. I was measuring about 600VDC when I did this. OOPS! This has been a good meter and I would like to repair it. Thanks for any help you may be able to give.
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Post a clear focused color picture that we can actually see something. The one posted doesn't show much detail and is blurry and out of focus.
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Maybe this one is a little better.
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Set up on a Fluke 175. 177 should have same configuration.
PTC, fusible resistor and MOVs.
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I'm off to bed. Picture still is too blurry. Go outside in the sun tomorrow and use macro mode on your camera.
We also need to see both sides of the board?
What were you trying to measure? The Fluke should survive any 600VDC oops moment.
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Set up on a Fluke 175. 177 should have same configuration.
Not necessarily. There are at least 3 different versions of the 17x pcb. The input protection components while similar may have changed. In addition, some resistors on his board may be toast, but we can't see them clearly. The pic you provided is a good example of what I mean be clear focused.
@OP. If you want a doctor to perform skillful surgery on you, don't you want him/her to see a clear focused picture of the xray? See the analogy?
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175 and 177 are the same meters. The only difference is the backlight on the 177.
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Got a different camera. I will clean the PCB tomorrow and post another one. The picture posted above is what this one is supposed to look like. Thanks for your help and patience.
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That looks as if the protection components actually caught fire and the PCB is carbonised. I would have big reservations about whether that damage can be safely repaired, especially if you are in the habit of measuring 600V supplies.
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How could this happen at 600V DC?? What range were you in? Ohms?
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I do not know what caused this. I was measuring the output of a transformer just after the rectifier and the last stable reading I took was 575 VDC. I moved the probes to the lower winding and the AC voltage was low, so I went back to the rectifier on the AC setting and read about 75VAC then switched to DC setting and was reading about 80 VDC. This is when I noticed the smell and shut down. It appears that what I think is an MOV (The black component in your picture just above the pos terminal) may have failed but that does not explain why the 2 caps above overheated. Is there a print available for this circuit? I cleaned the area up this morning and took some fresh pictures. I am posting the best one of the area. The 200K chip resistors measure good. I believe with some creative PCB repair and correct components I can repair the meter.
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A number of comments/suggestions.
1) For those wondering about Fluke's lifetime warranty, the user manual for the Fluke 17x series lists the terms and conditions. I can already say that one look from Fluke customer service and they will deny warranty as this meter was "abused".
2) Remove the white plastic rotary switch and look for damage. It wasn't until I suggested this person remove it that the problem became apparent in this thread.
https://www.eevblog.com/forum/repair/fluke-787-repair-any-idea/ (https://www.eevblog.com/forum/repair/fluke-787-repair-any-idea/)
3) You will not find a schematic for the Fluke 17x series.
4) Before ordering any components, for testing purposes, I suggest you desolder/remove the 3 blue MOV or what is left of them, the 1k ohm 2W fusible resistor, and the black PTC that is blown in half (closest to the input jack).
5) After removing these components, clean the area with IPA and remove as much of the carbon residue as it conducts. See
http://mrmodemhead.com/blog/ideal-carbon-footprint/ (http://mrmodemhead.com/blog/ideal-carbon-footprint/)
6) For testing purposes only, replace the fusible 1K ohm resitor and PTC with a 1k ohm regular resistor. The MOVs can be left out for testing purposes.
7) After installing the two regular 1k ohm resistors, see if the meter works on functions on LOW VOLTAGE only. Keep voltage less than 30V. Check resistance as well on all ranges.
8] If meter works, getting the exact rated components will be problematic. I will explain further after you verify the meter still works.
9) Post clear focused pictures of the cleaned up area with the carbon residue removed so we can see.
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I was measuring the output of a transformer
What device was this transformer in? Microwave? Radio?
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175 and 177 are the same meters. The only difference is the backlight on the 177.
I think you misunderstand or I didn't explain clearly when I mean pcb revision levels. So let me try again with a concrete example.
In this thread,
https://www.eevblog.com/forum/testgear/fluke-77iv-and-179-differences-with-teardown-photos/msg805040/#msg805040 (https://www.eevblog.com/forum/testgear/fluke-77iv-and-179-differences-with-teardown-photos/msg805040/#msg805040)
Robomed's 177 input protection is clearly different in some areas. The most obvious is the thick thin resistor vs the five 2003 SMD resistors. Additionally, the MOVs are red colored which may suggest a different value, specs, manufacturer, etc vs the blue colored MOVs.
Fluke doesn't publish any service manual or schematic and doesn't document the pcb revision changes in any public manner for the 17x series meters.
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You will have to mechanically remove (grind off) ALL of the parts of pcb that are different colour from normal FR4... If you can do that and keep the board in one piece, you can epoxy in place something to replace removed material.. After that you repair all the components and hope nothing else is damaged...
I personally would not trust a meter after such damage... Especially for high voltages.. It could be relegated to work on car or something.. But not 220V AC, not to mention more...
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175 and 177 are the same meters. The only difference is the backlight on the 177.
I think you misunderstand or I didn't explain clearly when I mean pcb revision levels. So let me try again with a concrete example.
In this thread,
https://www.eevblog.com/forum/testgear/fluke-77iv-and-179-differences-with-teardown-photos/msg805040/#msg805040 (https://www.eevblog.com/forum/testgear/fluke-77iv-and-179-differences-with-teardown-photos/msg805040/#msg805040)
Robomed's 177 input protection is clearly different in some areas. The most obvious is the thick thin resistor vs the five 2003 SMD resistors. Additionally, the MOVs are red colored which may suggest a different value, specs, manufacturer, etc vs the blue colored MOVs.
Fluke doesn't publish any service manual or schematic and doesn't document the pcb revision changes in any public manner for the 17x series meters.
I didn't mention anything about values, only layout, which is clearly the same as the one on the 175 of the same vintage I posted.
Robomeds' 177 is old (2000 vintage). The thick film resistor is not part of the protection circuit and there is a good chance that the PTC, fusible resistor and MOVs all have the same values across all meters of that series.
The PTC is blown, showing that the overload probably didn't happen on the voltage selection. There is a fair chance that the fusible resistor is still ok, although a little singed.
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Thanks for all your replies.I did as retiredcaps suggested, cleaned and measured PCB to make sure no carbon trace was there, and meter fired up. Hooked up to a battery I am charging with my other meter for comparison and it is a little off but that is probably because of the resistors I used. Does anyone have any values or part numbers for any of the components?
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That's one crusty looking meter !. Frankly its not worth the effort and cost of repair, not to mention the now compromised safety when there are many other "every ones favorite auction site" options in your country.
Simply put its likely you will be measuring similar circuits to what the damaged the 177 right?. So do yourself a favor and use this accident as the motivation to get a 'fresh' meter.
(and think carefully about what triggered this failure before trying a similar test with any other meter!).
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First, let me state that I'm not an expert in electronics and the following component selection below. This is all based on my own research and Fluke public documentation. None of the parts suggested below are actually from Fluke and the PTC and fusible resistor may have significant compromises in lowered performance ratings. As such, this meter, if repaired, may not likely meet its former safety ratings.
With that said, for less than $10 USD in parts, you can likely get your 177 working again. How you use it and whether you decide to use it again in a 600V environment is your choice given the feedback from other members.
1) MOV/varistor - The blue MOV used in your 177 seems to same ones used in other Fluke meters like the 87V. See
https://www.eevblog.com/forum/testgear/fixing-a-fluke-87v/ (https://www.eevblog.com/forum/testgear/fixing-a-fluke-87v/)
2) PTC (thermistor) - Since there is no public documentation, my own research suggests this might be 1.1k ohm 1000V specification. While I have found a suitable possible replacement, part number YS4020, no one reputable like digikey/mouser seems to stock it. The closest I found is
Epcos 500V PTC 1.1k ohm (NOTE: This is a 500V PTC, not 1000V)
http://www.digikey.com/product-detail/en/epcos-tdk/B59774B115A70/495-3890-ND/652053 (http://www.digikey.com/product-detail/en/epcos-tdk/B59774B115A70/495-3890-ND/652053)
3) fusible resistor - In the other Fluke meters that have a service manual/schematic, this is traditionally been a 1k ohm 2W fusible resistor. Finding one is difficult and the only one that meets the criteria of "fusible" is NTE F2W210 back in 2013. See
http://mrmodemhead.com/blog/fluke-87-fusible-resistor/ (http://mrmodemhead.com/blog/fluke-87-fusible-resistor/)
Recently on Oct 2, 2016, someone on another forum has suggested another alternative, but from reading the datasheet, I don't see the word "fusible" in it and don't know if "fusible" is equivalent to SPH series "failsafe" resistors.
http://www.antiqueradios.com/forums/viewtopic.php?f=8&t=308261 (http://www.antiqueradios.com/forums/viewtopic.php?f=8&t=308261)
Comment 1. One possible way to get potentially genuine Fluke parts is to buy a "as is" or "broken lcd" screen Fluke meter and use it as donor parts.
Comment 2. Your meter can be cleaned up nicely. I have purchased used Fluke in your cosmetic condition after some gojo and scrubbing, the yellow holster looks pretty newish. See
http://mrmodemhead.com/blog/dirty-multimeter-clean-up/ (http://mrmodemhead.com/blog/dirty-multimeter-clean-up/)
Comment 3. A similar sort of "oops" moment happened to a Brymen BM869. Initial pictures looked bad, but owner was able to repair it to a working state. Again, whether the repaired meter meets its UL listing and rated safety specifications is another story. See
https://www.eevblog.com/forum/repair/brymen-bm869-meets-high-voltage-in-real-world/ (https://www.eevblog.com/forum/repair/brymen-bm869-meets-high-voltage-in-real-world/)
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retiredcaps: You have been extremely helpful. Thank You very much for doing so much research to help me. I promise to clean it up when I get it repaired. The meter has been very faithful to me for several years and I used it in very bad environments. It is a prime example why Fluke meters are widely used by people who depend on them. I do like your idea of purchasing a donor meter for parts though. I will check into it. It was a microwave transformer I was testing. I will be using a high voltage probe next time I check one.
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I do like your idea of purchasing a donor meter for parts though. I will check into it.
Try not to pay more than $25 USD on ebay/craigslist/pawn shop for an "as is". It may take patience, but I know first hand it can be done. In fact, some of those "as is" meters work perfectly.
If the CDN $$$ were stronger and USPS shipping didn't increase nearly 100% to Canadians, I wouldn't have even mentioned the tip above. ;)
It was a microwave transformer I was testing.
That is what some members were speculating on the Brymen thread, but the OP never answered any of my questions regarding that area even though I asked three times. I ask not to embarrass, but to understand what else might be wrong with the meter in such a given scenario.
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I have the same model, but the damage mine suffered isn't as visible (visible at all).
17x-3001 rev 012 , assy rev 014
It was set on mA when I accidentally discharged a 2000microFarad cap at around 200V, so it was probably a single pulse.
Crap soldering stands out.
Swapped the upper diode with the lower one since I saw they were the same, and there was more space lower for the bigger replacement.
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Remote troubleshooting is difficult so I have some questions/suggestions.
Let's get a baseline of what is working.
1. Was the HRC fuse in the mA fuse holder? Or was a glass fuse or bypassed by a wire?
2. What does the LCD show with no probes when set to ohms?
3. What does the LCD show with no probes when set to DCV?
4. What does the LCD show with no probes when set to ACV?
5. What does the LCD show with shorted probes when set to ohms?
6. What does the LCD show with shorted probes when set to DCV?
7. What does the LCD show with shorted probes when set to ACV?
8. Does DCA amps work at all with a good known fuse?
9. Does DCmA amps work at all with a good known fuse?
10. What is the input impedance of the 177 when it is set to DCV?
11. What is the input impedance of the 177 when it is set to DC mV?
12. The Fluke 177 is almost equivalent to the Fluke 77 IV. Mark at
https://www.eevblog.com/forum/repair/fluke-77-repair-184173/ (https://www.eevblog.com/forum/repair/fluke-77-repair-184173/)
has schematics.
13. For the backlight, this may yield some clues in troubleshooting.
http://mrmodemhead.com/blog/fluke-77-iv-copper-corrosion/ (http://mrmodemhead.com/blog/fluke-77-iv-copper-corrosion/)
14. What does the LCD show with a 1k resistor?
15. What does the LCD show with 5V DC reference?
16. What does the LCD show when plugged into mains?
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White square capacitors https://www.eevblog.com/forum/repair/fluke-289-woes/125/ (https://www.eevblog.com/forum/repair/fluke-289-woes/125/)
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1. There wasn't a genuine HRC fuse, a 0.1mm copper wire was strung across
Jumping the fuse may have killed the main IC.