PM2 corrosion (photos)

[LCGarage]

I just got mine out of storage, display not working. Read up on PM2 problems here and sure enough it was corrosion from the batteries on both sides of the board. Bad enough to ruin the contacts under key pad.
Will try to clean the lcdisplay contacts next.
Any one ever get theirs working again after this much damage?

Corrosion near batteries:


damaged traces under key pad (after brushing):

[Carl Watts]

Yes I get them going again frequently in this mess.

Remove the board with the 8 screws.

Remove the LCD display by using a small phillips screwdriver running along the Elastomer strip by the board to "Break" the stick to the board.

Hit the board with Vinager and a toothbrush. You should notice the corrosion "Bubble" as it gets attacked by the vinager. Rinse the whole board in hot water and dry immediatly with compressed air.

Reassemble and test. Unfortunaly it probably will still not go as the corrosion has eaten through some tracks and it needs further repair but it's worth a go.

[LCGarage]

Will try with vinegar next and keep you posted. Great advice.
I appreciate all of your help on this one (on previous posts too)! Very, very helpful.
If it doesn't work at least I know why.

[LCGarage]

Here's the board with cleaned up pads and components, at least compared to the begining.




But still wasn't getting 3V to the IC....due to an open via. A small strand of wire was used and it worked!


The display came on BUT was drawing ~60mA. Further cleaning show a missing solder connection on the other IC.




This lead was soldered back down and thay dropped the current back down to ~2mA (when on)....much better!!!


I now have a working PM2!


Hope the photos help and go well with all the great advice/ tips provided by Carl.

[Carl Watts]

Great photographic work, what sort of a camera did you use to get those sort of close ups ? must have been a camera microscope ?

You got pretty lucky to get it going again. The standby current should be very low like 0.06mA normally to about 0.09mA max or it will go through the batteries in a few months or even less.

Usually I would remove the MAX859 and replace it if it was in this condition, there is also a via under it that can fail.

I finish the job with a clearcote using a PCB conformal coating like Electrolube CPL in the battery area to prevent future leaks eating anything. Hopefully it will run for a few more years at least if you nuetralised the corrosion.

[LCGarage]

Yes, I used a mircroscope/ digital camera...we have one at work.
Will use as is for now, but expect to have it open again for more cleaning and/or replace that 859....and add coating.
Thanks again for the help!

[senbluto]

Just bought a C2 with a non-working PM2 and, to no one's surprise, found battery corrosion. I did a quick looksie on the board and found R37 (15K) ohming out around 3 megaohms. I also found leads 11-13 (11: V ss, 12: V LCD and 13: V backplane 0) on the Philips LCD driver with severe corrosion. I haven't had the chance to neutralize and remove the battery acid yet, so I cannot tell if the leads are completely gone.

Does anyone have any experience with replacing these components? Does anyone know any repair companies in the U.S. that specialize in SMT repairs? I would do it myself, but I don't currently have access to the specialized SMT equipment needed to pull off this feat.

Thanks!

[Carl Watts]

They are very hard to repair if the acid goes under the LCD driver. There are many tracks under there and it is very difficult to keep the fine copper wires you need soldered to them while you reflow the Philips LCD driver IC back on. Also the boards are now getting quite old and the two layers delaminate quite easily if you overdo the PCB pre-heat to get it off. Get the vinegar onto it and repair any obvious faults first, only pulling the driver as a last resort.

[LCGarage]

Well, my PM2 started acting up again....so I upgraded to the PM3 and retrofit handle (to replace the wooden one).
What a difference that new handle made (and for only $15)!

It's like a new machine and like logging/ monitoring the data via the laptop.

[Ballyrotter]

Hi there

I am also having problems with my PM2 after the usual leaking battery faux pas.

I have cleaned it up and, as well as a bit of track corrosion, I can see that the 3 very small capacitors have blown in the bottom right of the board. Anyone know if you can get replacement capacitors?

Thanks all.