Fluke 87 button problem (solved)

[pro-sl]

Hi everybody, I have an older Fluke 87 multimeter that is working fine except that the 8 push buttons on the unit don't work well anymore. Its always a gamble if they work or not, pressing softly or harder, from different angles...it is really hard to apply just the right pressure for them to just work once and not 2 or 3 times in a row which makes choosing ranges and functions pretty difficult.
Cleaning underneath the buttons with isopropyl alcohol or deoxit helps but it only lasts for a few days or weeks, then I have to open the meter up again and re-apply.
Does anybody have the same problem or a solution to it. I am wondering if a new button pad will help but I bought the meter used years ago and am not sure if I can get replacement parts from Fluke. Thanks, Stefan

[retiredcaps]

Ebay seller a-fluke has a replacement for $14.95 + $2.25 USD shipping.  I'm not affiliated with ebay or a-fluke.

http://www.ebay.com/itm/371291342508

It might be possible to use the Fluke 83/85 keypad?  It is priced at $5.95 so you save $9.

http://www.ebay.com/itm/371177929577

There are two caveats.  First, obviously the backlight softpad is shaved down, but on the back side photo, the pad is still present.  Second, the shape of the pads are different.  The 83/85 is round and the 87 is oval.

I have both meters and can try the 83/85 pad in the 87 later tonight.

[Lightages]

There is also the possibility that Fluke will fix it free under warranty!

[retiredcaps]

I attached two pictures.

One shows the original Fluke 83 and 87 keypads.  As you can see, other than the color difference on the back, the size of the circles are identical.

In the other picture, I put the 83 keypad into the 87.  It works as I expected.  The picture shows autohold, backlight on and 20,000 count mode.  So the hold, power on backlight to get 20,000 mode and backlight buttons work.  All the others works as well, but I didn't bother taking pictures of it.

If you can live without a backlight and 20,000 count mode, you can order the cheaper 83/85 keypad.  Or you can carry a wooden stick to depress the circular keypad like I did.

PS. The second picture is handheld with flash off so I could show the backlight working, but is a bit blurry.

[retiredcaps]

There is also the possibility that Fluke will fix it free under warranty!

He bought it used and if this 87 is the original (series I), Fluke HQ will likely not honor the lifetime warranty.  If, on the other hand, this is a Fluke 87V, then he might have a slim chance of getting replaced under warranty for free despite buying it used.

[pro-sl]

Thanks for all the effort retiredcaps. It is an original 87 so no more warranty I am sure. I think I will just go with the 87 replacement pad, never thought about searching for it elsewhere than Fluke. I am still curious how the pads can wear out over time but I am sure a new one will fix the problem.

[retiredcaps]

I am still curious how the pads can wear out over time but I am sure a new one will fix the problem.

Modemhead has done a lot of Fluke 87 repairs over at his blog, but I haven't heard of any problems here at eevblog, there or other forums about the keypad wearing out?

http://mrmodemhead.com/blog/

I have one more suggestion, but I need to check the Fluke 87 service manual first.

[retiredcaps]

The service manual at

http://assets.fluke.com/manuals/83_85_87smeng0500.pdf

shows the 87 schematic.

There is a very small chance that cleaning the pads on the pcb and the main IC pins 64-69 with a generous amount of IPA might solve your problem?

You didn't mention if you cleaned the pads on the pcb with IPA (not deoxit).  Make sure the IPA dries thoroughly before re-assembly.

[retiredcaps]

BTW, cleaning the pcb keypad contacts is just like cleaning the pcb lcd contact pins.  See

http://mrmodemhead.com/blog/fluke-8x-faded-lcd/

[helius]

the button membrane is rubber, selectively impregnated with carbon. over time as the rubber stiffens and cracks, the carbon is no longer able to adequately conduct over the whole pad area. it affects rubber switches in (musical) keyboards, calculators, and appliances, even some computer keyboards. there are also kits to attempt to "rejuvenate" the rubber and restore the conductive coating: http://www.mgchemicals.com/products/prototyping-and-circuit-repair/circuit-repair/rubber-keypad-repair-kit-8339/

[pro-sl]

Thanks everybody for the detailed info I really appreciate it. The modemhead website is really great, will do some reading there.

[retrotubeguy]

Cleaning both the conductive pads and the PCB contacts should fix it. Or you could try the conductive chemicals mentioned. I would be surprised if the cleaning with IPA didn't work.

[McBryce]

I had a similar problem on a device where a new membrane wasn't available. The carbon layer on the rubber had cracks and wasn't conducting properly anymore. I just cut the carbon layer off with a sharp blade and "borrowed" the carbon layer from an old TV remote, which I then glued onto the membrane. Still works fine after several years of further use.

McBryce.

[edpalmer42]

I had a similar problem on a device where a new membrane wasn't available. The carbon layer on the rubber had cracks and wasn't conducting properly anymore. I just cut the carbon layer off with a sharp blade and "borrowed" the carbon layer from an old TV remote, which I then glued onto the membrane. Still works fine after several years of further use.

McBryce.

I recently did that to a Fluke frequency counter.  Make sure that after the repair, the carbon layer doesn't stick out more than it did before.  That will change the feel of the button or, in the worst case, short out the contacts even when the button isn't being pressed.

Ed

[Muttley Snickers]

I had a similar problem on a device where a new membrane wasn't available. The carbon layer on the rubber had cracks and wasn't conducting properly anymore. I just cut the carbon layer off with a sharp blade and "borrowed" the carbon layer from an old TV remote, which I then glued onto the membrane. Still works fine after several years of further use.

McBryce.

+1....I have a stack of replacement membranes for some equipment that we work on and had to graft the pads onto my favourite cordless phone which is a Siemens Gigaset, I did that for a couple of buttons years ago and they still work but now the others are playing up so I will need to get the scalpel out and go at it again. I used some really thin super strength double sided tape as I found some adhesive glues wont stick to silicone membranes very well, I watched a video where they used pencil graphite and PVA glue to make a paint so I might try that first and save some bandages, these phones are generally hard to get down here and not cheap so at least this may suffice until I can find a replacement phone.

Siemens Gigaset.... ....worth every effort.

Muttley

[pro-sl]

Cleaning both the conductive pads and the PCB contacts should fix it. Or you could try the conductive chemicals mentioned. I would be surprised if the cleaning with IPA didn't work.

I first cleaned both with IPA. That helped a little but not for long, then eventually I treated it with some deoxit gold. Then with IPA again etc. After every treatment it would last for a while but eventually have the same problems again.
I ordered a new pad and will report back how it performs.

[McBryce]

+1....I have a stack of replacement membranes for Bosch alarm codepads and had to graft the pads onto my favourite cordless phone which is a Siemens Gigaset, I did that for a couple of buttons years ago and they still work but now the others are playing up so I will need to get the scalpel out and go at it again. I used some really thin super strength double sided tape as I found some adhesive glues wont stick to silicone membranes very well, I watched a video where they used pencil graphite and PVA glue to make a paint so I might try that first and save some bandages.

Siemens Gigaset.... ....worth every effort.

Muttley

I tried pencil graphite and even silver conductive paint first. Both only lasted a few button presses before it failed again.

McBryce.

[pro-sl]

Okay, I got the replacement pads today and now my meter works like new again. Not sure if the graphite coating was gone or if it has something to do with the shape of the buttons. The old pad had round, the new pad has oval buttons that are much bigger. I can not see anything on the new button pad that looks like a coating of some sort, maybe it is fused into the rubber? Anyways, I am glad this meter is finally working the way it should. Thanks again to everybody for the tips.

[retiredcaps]

Anyways, I am glad this meter is finally working the way it should.

Come back in a month or two and let us know if it still working or not.

[pro-sl]

Yes, wondering myself if this thing will hold up. I do not use my meter to often, maybe 3 to 4 times a week for between 1min to 5min work time. But I will follow up, good idea.

[pro-sl]

Here is a very late follow up. I have been using the meter with the new pad for over 2 years now approx. 5 times a week and it is still going strong.