Gossen Metrahit X-Tra M240A Dead, Battery Leak Repair Help (FIXED!)...

[Mechatrommer]

short story long... 3 months ago i ordered this... more than a month, tracking number was useless (UPS deutch should be good but otherwise), after tired waiting and seller did not replying to help, i opened paypal dispute and claim, so i got my money back, left negative feedback and seller never come back again, so i thought this "scam" ended.. but today when searching for another parcel, this parcel showed up from nowhere in the post office.

after opening up, the DMM wont turn on, so there are drooling batteries inside, cant be sure about german technology (attached batteries' picture) but i guess its a knock off, hi tech doesnt drool around here. the 30 cents batteries inside a $1000 DMM you can see affected area before and after clean/repair pictured below. but unfortunately the DMM still refuse to turn on, so... any hint where to start? to help jumpstart my repair pace. so far i only checked battery connectivity around components cleaned / battery tab, some nodes register 2.7-3V so i know battery tab to pcb is not broken. and i managed to snap one of the thick metal connection from input plug to pcb to pieces (to enable pcb removal) bummer! i will come back to this soon and then, always too many tasks at hand... i wish to minimize intrusion so i will not poke where i should not esp calibrated and precision components that made this device so high. thanks for your help...

about the seller, i sent him a message... i copy here so if any reader is a ebay seller, sometime a scam is not a scam...

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hi sorry to interrupt you but this just to give you an update that i'm not a spam. when i searched for another parcel in post office, your parcel showed up, i wish to pay you back but there's problem, the unit is dead, i think there are few reasons this problem raised:

1) you choose poor tracking post office system (deutch post non updating tracking number)
2) you put wrong address, correct address is Lot 36, but you wrote Lot 3. so postman cannot reach my address and they put parcel idle in their office.
3) the unit is dead due to battery leakage. i tried to repair and clean it but it still dead.

as i said, i wish to pay back your lost, but this unit is not working either. so i dont know what to say. i will try to ask advice from friends to further repair this unit if possible. any comments from you will be appreciated. thanks and sorry for this inconvenience.

best regards,
Shafri.
and his refusal to reply to my last messages (before claim) to ask the item whereabout (since it cant be tracked) has raised my alert lamp to 90% PWM that this is a scam on seller side. but it turned out not to be the case, only few screwing up, and its screwed...

[coromonadalix]

As others will say, you need to neutralise the corrosion,the alkaline residues ....  do a proper cleanup, and try the gently scrape any gunk off the cpu pins without creating stress  etc ...

When all is done and rebuilt   you can apply  some pcb coating varnish ...

[Mechatrommer]

if i have time i'll remove the mcu altogether with hotair, there are too many gunks still trapped under the pins. but dead means either  something shorted, or got disconnected. visually under microscope, i cannot spot this 2 issues. i hope no component is dead...

[retiredcaps]

I would dunk the entire board with IPA and scrub gently with a clean toothbrush for 30 minutes to 2 hours.  You may have to do multiple IPA baths to remove most of the damage.

Afterwards, let it dry thoroughly and then start doing some measurements and tests.

[Mechatrommer]

i dont think i want to do that, that risk changing some resistors value or what, introduce more leakages between ic pins and what not (due to my IPA impurity). that may change calibration and hence reading precision. i will only touch the affected area as battery spills is only on that small area. the rest of the area that are not spilled still in clean condition, as a rule, dont fix it if its not broken.

[coromonadalix]

Yeah 

I personally would not remove any parts, unless really really needed, it may get worse,  with a very fine needle, try to clean betwen the cpu pins,  had to do this on a pcb washing machine, some water managed to get to the display, and dripped on the display controller,  had to remove  "green stuff"  between the display controller pins

And for the finishing "pins cleanup"  i used somekind of an fiber glass composed "5mm" round brush, gently moved back and forth,  i have at my job a mg chemical brand tin liquid,  applied a few drops  and after an hour, cleaned the pcb  with an pcb cleaner   Atron SC205  and deionized water

Works fine up to this day

But the meter has more damage,  just be careful, take your time,  dont rush anything, and you will succeed. 

[Mechatrommer]

i removed the mcu last night, cleaned underneath and resolder. put the batteries, still no go, but sometime, few unit symbols lit, intermittent and then hanged, try remove,reinstall batteries again, its dead again, so i almost lose hope, in the end, thinking that its already dead, i just put it aside with batteries installed. i think maybe i can see some burnt element later or flat batteries so i will know something is shorted. but after few minutes sit on the bench, when i hit the power button, it beeps and turned ON! i tried again several times from last night, now its consistently to be working again and ON everytime. so just now, resolder back the input connections, metal shields and everything, put back together and test some measurement. right! calibration is unknown, so now i have one more meter just to confuse me even further. attached showing reading from 2 china meters beside the xtra. the china meters read very closely together, so i'm not sure which one is correct. reference is AD584JN (the best i got here, how poor) 2.5V, 5V and 10V. and the xtra showing 0.6mV when probes shorted together. the other 2 china meters are correctly showing 0V. so maybe this gossen is out of calibration.

one thing i made stupid mistake (besides broken connection to input plug) is as i left the DMM on the side of the bench, i marked the protecting plastic just to remind me later. but it turned out the plastic "absorb" the permanent marker ink and cant be erased with anything without destroying the plastic, even with the venerable thinner. so it toasted (5th picture).

so as a conclusion, the biggest trick is, after cleaning from battery leakage, try reinstalling new batteries and let it sits for sometime. not sure what happened, maybe this meter doesnt like to be turned OFF for long period of time, something needs to charged up slowly? or maybe some deterioration components inside i dont know. i just got lucky i think, i didnt fix anything except cleaning it and look out for disconnected traces, which i didnt find, only damaged to solder masking.

 fwiw, ymmv, cheers.

[Terry01]

Nice fix! 

[Mechatrommer]

as i said i just got lucky... and another trick to think of is dont store this meter with its face down (which i think what happened in its previous house) battery leak will enter and screw the pcb and components. store it with its face up or standing straight, this way, any battery drool will flow to the plastic casing which i think will not do any harm. ymmv.

[tautech]

Good fix, you were very wise to get on to it smartly and not throw it in the drawer for a rainy day. 

No way it would have been that simple if the mess under the MCU was allowed to continually fester away.

as i said i just got lucky... and another trick to think of is dont store this meter with its face down (which i think what happened in its previous house) battery leak will enter and screw the pcb and components. store it with its face up or standing straight, this way, any battery drool will flow to the plastic casing which i think will not do any harm. ymmv.

More wise words....but common sense really......poo doesn't run uphill. 

[Mechatrommer]

No way it would have been that simple if the mess under the MCU was allowed to continually fester away.

as far as i can see, the functioning is still intact (no broken traces), the damage hasnt got so far beyond solder masking. unless the mcu is sensitive to current leakage created by "oxidized/melted" solder mask, maybe the DMM can still function again with "put new battery and rest" trick without me opening and cleaning the thing up in the first place. but this thing will surely need cleaning up, just to avoid further damage to the functioning level, ie broken traces due to eaten up copper, and worst broken IC pins.

as i said i just got lucky... and another trick to think of is dont store this meter with its face down (which i think what happened in its previous house) battery leak will enter and screw the pcb and components. store it with its face up or standing straight, this way, any battery drool will flow to the plastic casing which i think will not do any harm. ymmv.

More wise words....but common sense really......poo doesn't run uphill. 

but eventually some people did it, like this meter. since this problem can happen only after years in storage, seldomly happened, we usually forgot about it and just buy new again when problem found, but this is $500+ DMM, one should be mindful about this matter. and its also more related how the device is designed (sealed), some of my devices, such as few china fan remote controls here that uses 9V battery can be stored in any orientation without function damage because the battery is quite isolated/separated from pcb, they all experienced quite severe battery leakage and rust marks on the plastics battery compartment mind you, but still functioning well. the only damaged are the battery tabs, but they can be easily replaced. the only way to allow drooling battery sneak into the pcb is by laying it upside down on the infrared led at its top which is impossible since it cant stand that way on its own.

imho from battery leakage aspect, this gossen meter is poorly designed, or didnt take this matter into consideration. battery tabs are very close to populated components (luckily not on the measurement sensitive parts), it should have some sort of separator, add-on pcb, rubber seal to battery compartment or retention area/absorbant in case battery liquid got sneaked in. we can see the inside pcb just by looking trough the battery compartment, about a mm by 5 mm wide opening happy to swallow any less viscous secretion squirted from there.

[Mechatrommer]

just another update, i just got a new and calibrated (Jan2022) Fluke 87V at my hand recently. so now i can ascertain the measurement dissimilarities i saw 2 years ago, and know more who to trust, who to not... so i dig my AD584 voltage reference again to remeasure, here's the result...

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measurement on 220513, voltage reference AD584JN
temperature sensor using Vici VC99 or Fluke 87V sensor (depending on connector suitability)

DMM/Mode (Vdc) 12V SLA Batt 10V (±0.3%) 5V (±0.15%) 2.5V (±0.075%) Room Temperature/Built-in sensor (ºC)
-----------------------------------------------------------------------------------------------------------------------------
Fluke 87V 12.562 10.000 4.999 2.499 28.3/-
Gossen Metrahit XTra 12.63 10.013 5.009 2.507 26.1/-
Uni-T 71A 12.568 10.005 4.999 2.498 -
Vici VC99 12.55 9.99 5.009 2.503 25/25
Aneng 8002 12.56 9.99 4.999 2.499 28/28
Aneng Q1 12.55 9.99 4.999 2.498 30/30
-----------------------------------------------------------------------------------------------------------------------------

so the Gossen that should performs pretty well as and closest to the Fluke 87V is now the worst, with Vici VC99 following it from the back... so Gossen is now the prettiest but the dumbest DMM in my collection. it maybe out of calibration due to my repair, or since it with the original owner, now i know. so i'm happy that i can verify my other DMM (Aneng and Uni-T) esp my aging 12yrs old Uni-T UT71A that they are pretty close and still acceptable to Fluke 87V standard. maybe i need to refurbish its aging buttons with carbon paste so they can functional comfortably again as my main day to day outside lab DMM. fwiw...

ps: since the last post in 2020, i've re-open the Metrahit twice to repair again the rotten tracks inside (when turned on, dmm turn off immediately due to low battery detected, but batteries are new) including once yesterday, they seems to still be infested with the battery leaks chemical since its arrival at my lab in OP, even though i thought i've cleaned them very well. so its in quite ill condition from inside, sadly.

[Mechatrommer]

this night is my 5th repair session. in the last 4th session, traces got worsen and broken so i replaced the missing traces with copper wire, and add flux everywhere to avoid further deterioration from battery alkaline left over, but it turned out the flux introduced some instability to the functionality (missing digits etc) few weeks ago. noticing dave experienced the same issue on Fluke 3000 in his blog, reminds me of this metrahit. so i test again this meter tonight to be totally dead, so i clean up all fluxes, and re-dress the affected exposed traces with another flux brand with careful not to overdo it... the meter is alive again, its the 5th repair attached are the copper wires soldered as traces replacement. fwiw..

[wraper]

ps: since the last post in 2020, i've re-open the Metrahit twice to repair again the rotten tracks inside (when turned on, dmm turn off immediately due to low battery detected, but batteries are new) including once yesterday, they seems to still be infested with the battery leaks chemical since its arrival at my lab in OP, even though i thought i've cleaned them very well. so its in quite ill condition from inside, sadly.

That garbage remains under SMD parts like MLCC and resistors, and in vias. When it has got over components and it's not just a small spot, PCB should be cleaned in ultrasonic bath to wash that junk away from various crevices. Also for cleaning something like this IPA is a bad choice. I likely would use weak-ish citric acid solution to neutralize and remove alkali junk. And then wash it in ultrasonic bath again but with clean water to remove all of the cleaning solution from any crevices.

[Mechatrommer]

thanks for advice. i dont want to dip all the pcb in a bath just yet, i bought an ultrasonic cleaning bath few months ago to clean other stuffs though. maybe i will do that on this pcb as the last resort when i cant recover this meter by doing minor fix. the affected region is only small part near battery and mcu. if i want to do full cleaning i think i'll have to remove the mcu and other passive components to ensure thorough cleaning under the parts. that will take many hours including drying etc, so far i can only do quick fix, if its fixed then i leave it there, i can do other stuffs that i'm busy on right now. my theory is those exposed copper will undergo oxidization overtime, so by putting flux, i hope it can stop it, sort of replacement to the missing solder mask. i did cleaning with IPA, let it flow on the affected area several time in hope it will sneek underside of mcu etc, and then carefully blow with compressed air. i hope some of the junk will move away from the meter functionality. fyi, i think the battery tabs on the other side that was affected are neutralized now, they look clean and dry, there is no sign of further deterioration. so i dont have to cover that area with flux yet. fwiw..

[wraper]

The problem with IPA is that it's a nonpolar solvent. It dissolves organic stuff like rosin and fats. But it's pretty much useless at dissolving salts, so in this case basically the only cleaning action you get is from mechanical scrubbing. So a lot of not dissolved junk can still remain. Water is actually pretty safe for washing PCBs, most of the industrial PCB cleaning is done by water based solutions. You just need to remove any components where water can get in, like switches, microphones, non sealed relays, any sort of speakers. Some of them can be covered by sticky take, like buzzers if they are sealed on bottom side. They often come from factory with a sticker on top which sould be removed after washing.