EEVblog Electronics Community Forum
Electronics => Repair => Topic started by: archaelus on January 21, 2014, 07:25:04 am
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Hi all, I just bought a Fluke 289 as-is from ebay and I think it's been exposed to overvoltage.
Symptoms:
- Meter powers on fine
- Screen, setup, menus, ... are all fine
- Current measurements are fine
- DC Voltage reads 0 (0.00025V or something) under any input
- Other functions relying on the V input terminal do not work
After opening the case I've found that the PTC (MOV?) [RT1] on the voltage input channel (A) is blown in half, and the [R4] resistor that claims to be 1k?±10% is desoldered from the board. The second PTC/MOV [RT2] inline from [RT1] seems intact, and measures 1k?.
There's soot all over the varistors (?) [RV1], [RV2], [RV3] - these things are marked 05 K575 (unidentifiable symbol - looks like (backwards R)U ) and with what appear to be date codes. I'm guessing these are 575 V protection devices?
Can anyone help me identify the resistor [R4] and the PTC/Mov [RT1] (and [RT2]) so I can get some replacements? I'd also love to figure out what [RV1], [RV2], [RV3] are and some advice on how I'd test to see if they're still good.
Cheers,
-Geoff
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Here's a better shot of [RV1] - [RV3]
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Not sure if this helps, I did take shots on my 287 (should be similar to 289) like at your blown input area.
Sorry, currently don't have any other angles at this section, only this one.
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R4 is a 1K 10% carbon resistor, so probably still good if you don't want to replace it.
The MOVs should be replaced in case they got damaged. You can test them in the meantime for short circuit to make sure they don't affect voltage measurement.
I would think any low current 1000V PTC will do as a replacement, until you can identify the proper part number.
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Thanks BravoV, now I know what it should look like :) Can you make out the markings on the [RV1]/2/3 components?
Wytnucls - thanks, I did re-test the resistor and it appears to work if I clean all the soot off it. It's a little chipped, so I wouldn't mind replacing it if I can get a replacement easily enough.
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Sorry, I'm not planning to open up my 287 soon, also I'm on travel. :-//
But yours should be clear enough right ? and also don't think mine are different from yours.
Anyway, I guess this is the proof that how a well designed DMM input works, isn't it ? Looking at the charred area, the creepage gap really protects the precision resistor and other low voltage area. :-+
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R4 is a 1K 10% carbon resistor, so probably still good if you don't want to replace it.
Without a service manual or schematics, I can't be 100% sure, but from my own research, I believe R4 is likely a 1 k ohm 2W fusible resistor.
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Can anyone help me identify the resistor [R4] and the PTC/Mov [RT1] (and [RT2]) so I can get some replacements? I'd also love to figure out what [RV1], [RV2], [RV3] are and some advice on how I'd test to see if they're still good.
RT1 and RT2 are thermistors. They should read about 1.1 kohm. I believe these PTCs are 1000V rated. I did find a suitable replacement YS4020, but no one has it in stock?
http://datasheet.octopart.com/YS4020-Thermometrics-datasheet-11237.pdf (http://datasheet.octopart.com/YS4020-Thermometrics-datasheet-11237.pdf)
If you or anyone finds a supplier, let me know.
RV1, RV2 and RV3 are varistors. They should measure 0L or infinite resistance. See this thread regarding the markings and replacements.
https://www.eevblog.com/forum/testgear/fixing-a-fluke-87v/ (https://www.eevblog.com/forum/testgear/fixing-a-fluke-87v/)
As I mentioned, I believe R4 is a 1 k ohm, 2W fusbile resistor. See
http://mrmodemhead.com/blog/fluke-87-fusible-resistor/ (http://mrmodemhead.com/blog/fluke-87-fusible-resistor/)
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it is a 1K wire wound fusible resistor. Fluke seems to use the same one in most of their meters.
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it is a 1K wire wound fusible resistor. Fluke seems to use the same one in most of their meters.
Yes, the same body colored green resistor is almost present in every recent Fluke multimeter including your Fluke 101.
https://www.eevblog.com/forum/testgear/teardown-of-fluke-101-kit/ (https://www.eevblog.com/forum/testgear/teardown-of-fluke-101-kit/)
I have also seen the same green body colored resistor in some recent Brymen meters as well.
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Probably this one or similar:
http://www.ohmite.com/cat/res_ox_oy.pdf (http://www.ohmite.com/cat/res_ox_oy.pdf)
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There's soot
Don't forget to give the pcb an IPA bath and get rid of that soot as it may be conductive. See
http://mrmodemhead.com/blog/ideal-carbon-footprint/ (http://mrmodemhead.com/blog/ideal-carbon-footprint/)
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Thanks retiredcaps!
I think I've found the resistor at digikey http://www.digikey.com/product-detail/en/OY102KE/OY102KE-ND/823949?itemSeq=143019197&uq=635259137438645752 (http://www.digikey.com/product-detail/en/OY102KE/OY102KE-ND/823949?itemSeq=143019197&uq=635259137438645752)
I think the varistors are from Epcos, but I can't quite figure out the exact part. S05K575 doesn't seem to exist publicly. Maybe http://www.digikey.com/product-detail/en/V575LA10P/F3771-ND/1009609 (http://www.digikey.com/product-detail/en/V575LA10P/F3771-ND/1009609) ?
I'm still not sure what the thermistor part is - it's marked 'Thm' but has no other identifying marks - seems to be a 'leaded disc ptc' and 7mm wide by 4mm thick. Maybe http://www.digikey.com/product-detail/en/B59758B0110A070/495-3885-ND/600268 (http://www.digikey.com/product-detail/en/B59758B0110A070/495-3885-ND/600268) if it's 1000V rated. There were two of these things in series. The Fluke 87V repair suggested http://www.plccenter.com/en-US/Buy/GENERAL%20ELECTRIC/YS4020 (http://www.plccenter.com/en-US/Buy/GENERAL%20ELECTRIC/YS4020) ?
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I have to head out soon, but I'll look through your selection later tonight or tomorrow. I have looked in the past, but as you are probably aware, availability varies and new alternatives pop up.
In addition, let me say that I'm learning about multimeters/electronics and with no service manuals or schematics, everything is a best guess based on available information.
People buy and trust brand names like Fluke, Agilent, Gossen, etc for safety reasons. If you will be using this 289 in any sort of high voltage situation, you must get the proper parts to protect you and the meter. Some of these parts may only be available to vendors like Fluke and not to the general public.
On the other hand, if you are using this 289 for hobby use and low voltage, then you might have some more options.
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Indeed. Unless I have this thing repaired or serviced by Fluke, I'm not going to use it for high voltage work - I'm also going to put a big red warning label on it indicating it is no-longer Cat anything rated.
I won't be able to get the exact fluke parts, and even if I could - I can't certify this meter as safe. It would be nice to get it working for hobby low voltage work though.
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Indeed. Unless I have this thing repaired or serviced by Fluke, I'm not going to use it for high voltage work - I'm also going to put a big red warning label on it indicating it is no-longer Cat anything rated.
I won't be able to get the exact fluke parts, and even if I could - I can't certify this meter as safe. It would be nice to get it working for hobby low voltage work though.
Very WISE decision!
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Before ordering anything, I suggest you consider the following.
1) Desolder all the thermistors, MOVs and 1k ohm green body resistor.
2) Clean up all solder flux, soot, dirt, etc with a generous amount of IPA.
3) Replace the thermistors and 1k ohm green body resistor with "regular" 1k ohm resistors.
4) Leave the MOVs out of circuit. BTW, two of them look obviously damaged (blackened) and while the third (middle) looks visually okay, I wouldn't trust it and would replace it (only 65 cents).
5) Test your meter with low DC voltages and some known reference resistors.
If it all works with just "regular" 1k ohm resistors, now you can go about ordering replacements.
Since a lot of current Fluke models seemingly use the same components for input protection, I will try to write this generically for future readers.
Again, please understand that without official Fluke service manuals, BOM and schematics, that this is based on a best guess effort based on available public information and availability of parts to retail customers.
Thermistor (PTC)
The thermistor should be around 1100 ohm and I believe rated at 1000V. I believe a suitable replacement is YS4020 (made by GE), but no one has it in stock?
Your replacement, B59758B0110A070, is rated for 1000V, but the resistance is 7500 ohms according to the datasheet at
http://www.epcos.com/inf/55/db/PTC_12/PTC_OC_Leaded_380V_1000V_B_B750_B774.pdf (http://www.epcos.com/inf/55/db/PTC_12/PTC_OC_Leaded_380V_1000V_B_B750_B774.pdf)
B59774B0115A070, on the other hand, is 1100 ohm resistance, but the maximum voltage is only 550V. This may be a suitable replacement if you only measure low voltages?
Varistor (MOV)
The original MOVs look like they are rated for 575V. This thread has suggestions on a replacement and at two people report it seems to work (albeit, no one has probably tested them at high voltage).
https://www.eevblog.com/forum/testgear/fixing-a-fluke-87v/ (https://www.eevblog.com/forum/testgear/fixing-a-fluke-87v/)
Your choice, V575LA10P, is identical one to the above. Just remember, installing the MOVs might require some careful placement and possible leaning here and there to make it fit.
1k ohm resistor
Here is the area where I'm not at all sure what the resistor should be. We know it is 1k ohm +/- 10%, but we don't know the exact characteristics. Does it have to be fusible like the ones used in older generation Flukes? Or has Fluke changed the specifications?
Wytnucls's suggestion that it might be a Ohmite or similar is a good one. I don't see the words flameproof or fusible in the datasheet, but again it may not matter?
Your choice, OY102KE, is 2W. However, I can't tell by size alone if it is 1W or 2W either in real life or through photos.
Summary
For the 1k ohm resistor and MOVs, I believe you have reasonable choices.
For the thermistor (PTC), I'm not sure what ramifications the 7500 ohm will have.
PS. Did you buy this Fluke 289 in auction where you also got a Klein and Agilent meter?
EDIT: Fixed some typos and grammar.
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As far as I understand, the 1.1K thermistor is a current limiting device, just like the 1K resistor in series with it. The maximum voltage they would have to sustain between them is about 1000V, or about 500V each, when the three voltage controlling MOVs in series (assuming they are in series) will
short the supply clamp the voltage.
So a thermistor with an operating voltage of about 500V should be sufficient and three MOVs with a breakdown voltage of approximately 330V each would also be good enough for the job.
But don't take my word for it and double check with the pros.
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PS. Did you buy this Fluke 289 in auction where you also got a Klein and Agilent meter?
Heh, yes I did indeed. The agilent is next to repair - measurements using the voltage channel are pretty messed up (readings start at 0V then just climb up on their own).
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PS. Did you buy this Fluke 289 in auction where you also got a Klein and Agilent meter?
Heh, yes I did indeed. The agilent is next to repair - measurements using the voltage channel are pretty messed up (readings start at 0V then just climb up on their own).
Well if you want help, post a new thread for the Agilent and Klein. I hold no long term grudges against my ebay buying competition! ;) :-DD
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After fiddling around with a continuity tester, I think the 289's input protection circuitry looks something like this:
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The OY102ke ohmite resistors for R4 turned out to be way too big.
I'm pretty sure they're supposed to be this: http://www.digikey.com/product-search/en?WT.z_header=search_go&lang=en&site=us&keywords=OX102KE-ND&x=12&y=6&formaction=on (http://www.digikey.com/product-search/en?WT.z_header=search_go&lang=en&site=us&keywords=OX102KE-ND&x=12&y=6&formaction=on)
The PTCs seemed way too big and as someone else mentioned, the wrong resistance value, so I'm going to try http://www.digikey.com/product-search/en?WT.z_header=search_go&lang=en&site=us&keywords=495-3894-ND&x=6&y=12&formaction=on (http://www.digikey.com/product-search/en?WT.z_header=search_go&lang=en&site=us&keywords=495-3894-ND&x=6&y=12&formaction=on) or http://www.digikey.com/product-search/en?WT.z_header=search_go&lang=en&site=us&keywords=495-3890-ND&x=0&y=0&formaction=on (http://www.digikey.com/product-search/en?WT.z_header=search_go&lang=en&site=us&keywords=495-3890-ND&x=0&y=0&formaction=on) instead.
The MOVs also seemed way too big (common theme here), so I'm going to look at http://www.digikey.com/product-detail/en/MOV-07D821KTR/MOV-07D821KCT-ND/4318153 (http://www.digikey.com/product-detail/en/MOV-07D821KTR/MOV-07D821KCT-ND/4318153) and see if that works better. I figure that as they're connected in series, they probably don't need to be 1000V rated - more like 300-500VAC . (And as I don't intend to ever test the upper end of that range, it should be OK) - the lower voltage rated MOVs better match the dimensions ~5.6mm dia of the components I removed from the 289.
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Please report back and let us know if your new choices work or not. If they work, a picture of the repaired components and pcb would be appreciated so we can see how much room the new components take compared to the old ones.
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With the 7mm MOVs, the 1W fusible resistor and the 16ma 500V PTC, the replaced components look about the same size as the originals.
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Better yet, after putting it all back together, I tested it it with one of those little voltage reference modules from Ebay (http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=181302432217 (http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=181302432217)) against my Fluke 89 IV and got pretty good results I think.
The 89 IV gets pretty close to the readings supplied with the voltage reference unit (about as close as you can get with 50000 counts).
The 289 seems to read about 1-2 counts higher than the 89 IV, which I think is pretty great for my first successful repair.
I don't have any other reference to test it against right now (for resistance/capacitance/diode/temp measurements), so I think I'm going to leave it as is for now.
Thanks very much for the help all!
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I'm glad you got it working and that the 289 seems within its specifications. :-+
Buying something "as is" and paying a high price for it can end badly especially if the pcb sustained more damage or if the 289 required calibration. Luckily, the input protection worked and protected the meter.
Now, let's see pictures and your repair of the Agilent and Klein.
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Hi. I'm reluctant to resurrect an old thread, but I have a 289 here with the exact same HV burn dmg.
As many before me I have difficulties finding the exact same parts as the Fluke originals.
Tried random varistors, nope => crap. High capacitance range zero reading (~0.250nF) and resistances were out too for some reason, despite the varistors measuring over 1 Gohms.
So I'm thinking the originals must be very low capacitance parts.
Without varistors and with 1/4W 1k resistors in place of the PTC-s the cap zero reading w/o leads is 0.085nF. Dunno if that's ok or not. Other than that everything, including cap(at least in uF and up) range is in spec :-+
So my question:
would it be bad idea to use GDTs (like Bourns 2095-80-BLF) instead of MOVs there? Coud it be that the right MOV with the right capacitance could be somehow compensated upstream to cancel out their impact? Like, no MOV is sub pF anyways, right?
On the other hand GDT would be slower and 'clamp' harder. Perhaps not a good idea with the Low Z function.
Thoughts?
Thanks ahead!
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Tried random varistors, nope => crap. High capacitance range zero reading (~0.250nF) and resistances were out too for some reason, despite the varistors measuring over 1 Gohms.
If you remove the varistors completely, do resistance measurements work properly? If not, give an example of what is wrong. For example, if you measure a 1k ohm resistor, what reading do you get?
So my question:
would it be bad idea to use GDTs (like Bourns 2095-80-BLF) instead of MOVs there?
Yes. Changing parts that do not meet or exceed factory specs is a bad idea. Fluke has always used MOVs so stick with MOVs.
Answer the question above and then we can proceed.
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If you remove the varistors completely, do resistance measurements work properly? If not, give an example of what is wrong. For example, if you measure a 1k ohm resistor, what reading do you get?
Yes. Changing parts that do not meet or exceed factory specs is a bad idea. Fluke has always used MOVs so stick with MOVs.
Answer the question above and then we can proceed.
Hey, thanks for taking time to answer.
Yes, everything I have measured is safely in spec (2-3 counts out the most). I have a recently calibrated (also adjusted) BM869 and bag full of calibrated resistors that show pretty much bang on with the damaged Fluke.
Well, not like GDT-s are never used in multimeters. Keysight uses these in benchtops. The protection circuit could be slightly different, and there is no Low Z function in those.
Meeting or exceeding factory spec is how you look at it. GDT will have less capacitance, higher current rating, lower on resistance (which might be worrisome) and slower turn on, also perhaps not ideal. The slow turn on and low 'on resistance' gives me pause for now. MOVs that I have found don't work, too high capacitance. The S05K575 original could not be found, or at least I have not.
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I think the varistor should have a resistance of 1K, so there is a fusible resitor and varistor in series and each of them is 1K. Replace varistor with regular resistor for tries and see if the measurements are correct... I've replaced few of those, let me see what I've used
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Hello everyone,
I'm trying to restore 289 after a strong water damage. Now 289 is turned on, the display is work half other half is hard to see, measures the voltage normally, the current measures normally, but with the measurement of resistance there is a problem..
With no connection any resistor he shows ~3,6MOhm, if i change range up too 20M or 500M he shows ~26MOhm.
I measure voltage on all ranges with 10GOhm intput voltmeter
Range Out volt.
500 3,230
5K 3,069
50K 2,910
500K 2,749
5M 2,724
30M 2,628
50M 2,27
500M 2,627
Range 500Ohm-500K measure correct (i measure resistors with 1-5%), in range 5M he can measure resistance 1MOhm 2Mhom correct, but all above 3,6MOhm he cant see.
Here photo before and after ultrasonic clean https://photos.app.goo.gl/i1igHbYTkfpc5ZQe9
I think schematics similar to 867 multimeter https://yadi.sk/i/3GnY4aS0-KpUyg
Maybe someone at 287-289 can to measure the voltage on different ranges?
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Hello guys ! Need your help ! Bought a multimeter Fluke 289 without probes when you turn on the tester displays a message that the probes are incorrectly installed at all positions. I took it apart all the parts in place what parts can I check and how ? Two phototransistors each EA against each other what should be the resistance and photodiode ? I will be very happy people who was able to find a solution to this problem!Await the from you guys answer !
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Who can help me with this problem ? What to measure and what should show if the working condition of the radio components of this circuit ?