Elastomeric Connectors

[MrAl]

Hello,


I've read that the elastomeric connectors used on LCD displays are hard to work with unless you have a new one to replace it with if you remove the LCD.
Anyone ever work with these kinds of connectors, and if so, what were the results?

Thanks...

I forgot to mention that these connectors are often found on multimeters and other small devices that use LCD displays, and look like long and thin rectangular black, gray, or pink pieces of rubber that are found squashed between the LCD display and the PC board driver.

 

[Nigel Goodwin]

In my experience, once you disconnect them you have a hell of a job trying to get it to ever work again.

 

[MrAl]

Hi there Nigel,


Thanks, that was my experience too but i was hoping someone would have some magic at hand to use (har har)

I've read not to use alcohol either, which is a common cleaner for some electronic things. All i have found so far is that if the connector is removed it has to be replaced with a totally new one, mostly because the indentations are impossible to match up again (the indentations from the circuit board traces). I had a meter a long time ago i had taken apart because one segment of the LCD wasnt working. After removing the LCD to check everything out, i found a bad solder connection on one of the pins of one of the IC chips, and soldered it so it was solid. After replacing the LCD and firing the unit back up again, i noticed more segments were not working! I found that by pressing on the elastomeric connector (compressing) the segments would come back on, so i installed a make shift mechanism to help hold pressure on the LCD so it would press against elastomeric connector with a little more pressure. That lasted for quite a while, but then started acting up again some time later. Trying that routine again though failed and the meter was junk. That really bites though, having to junk a whole meter just because of one silly connector.

It's nice to know that i wasnt the only one to have this problem so thanks again for the reply

 

[jim pitman]

Boil the elastomeric strip.
I have a Fluke meter with LCD display that I've kept alive for years by boiling the rubber strip. It swells it a bit. It seems I have to do this once a year or so.
Interestingly this meter won't finish booting if the display doesn't work 100%.
Who ever heard of a functional ouput device having a conditional for booting?
I eventually got the manual and by golly if it didn't mention that the self test checks the integrity of the dispay. The program must measure the current consumed I assume.

 

[ModemHead]

Anyone ever work with these kinds of connectors, and if so, what were the results?

Can't say that I do it every day, but I've cleaned/repaired at least a dozen LCDs in the past few years, mostly DMMs but also a thermometer, a kitchen timer, and a telephone answering machine that I can remember. Every time except one I was successful, the holdout being the answering machine, and it ended up no worse than when I started.

I use denatured alcohol and cotton swabs. I clean both the zebra strip and the glass. The glass seems to collect a film from something that leeches from the elastomer, and it requires some effort to clean, with a generous amount of alcohol. I use a magnifier to make sure there are no cotton fibers or film left, and I'm careful not to touch the contact surfaces. Reassemble with everything in the same position it was before.

I've picked up a couple of used Fluke DMMs on eBay that had faded displays, and was easily able to fix both. (Saves money, the bidding isn't so crazy on those.) I also fixed the fading segments on my now-ancient original Fluke 87 a couple years ago, and it's still going strong.

That's my experience.

 

[tunedwolf]

Like most folks here, it's not something I have to do every day, that said, this is what I do when in a pinch...

I clean all parts in hot soapy water then rinse well. After a quick dry with a hair dryer I usually treat the rubber connectors to a good clean with some methylated soap liniment and leave them to air dry. I would normally use this for cleaning/ restoring general rubber components like pinch rollers etc. Being careful not to touch the connectors on the glass, I reassemble the display in the frame and offer the assy to the board making sure I clamp it back up evenly. I only ever pay attention to the glass orientation and not the rubber connectors, I figure that this trick will either work fine, or not at all. I have only had one failure, and this was due to the driver being farked, and have done maybe 30 displays of various sizes over years.

I could have just been lucky so far. I only ever do this when I have limited choices open to me at the time. I prefer to just replace these displays, but alas it's not always possible at the time. For some reason smaller displays, like 3 1/2 digit, 16*x and 8*x seem to suffer the most from this in my experience, usually manifesting itself as missing segments/ dots. I have always thought that the problem was chemical breakdown reducing the elasticity of the connector, rather than a conductivity issue, contamination issues aside.

rgds

 

[MrAl]

Hello again,

Thanks much for the info guys. I have a bit more grasp of the situation with these things now. I may actually attempt to fix an old multimeter i had that had a problem with the E connector and various means to keep pressure on it did not work. I think if i tried cleaning it with one of the ideas here it may actually work again. Would be interesting. All i have to do now is find it.
I was originally concerned because i had to take another meter apart recently and this meter was much more expensive and i didnt want to run into the same problem i had with that older meter. This new meter design was much better as the display and PC board were bolted together as a unit so that when you take the board out the display didnt get bothered. I guess they realized over the years that it would be better that way. With the old meter as soon as you removed the PC board the display got messed up. BTW i was finally able to fix the newer meter and it turned out that there was a second fuse hiding under the PC board that was blown! What a surprise. That meter had only partial functionality for several years because the manual never mentioned changing a second fuse, only the one fuse that is visible from the top without taking it apart. Strange. At least now it is fixed

 

[scottksmith]

Well guys, let me enlighten you. I am an electrical engineer with 50 plus years experience in hands on electronic instrumentation repair. These strips are pretty simple. If you look at them closely, they are nothing morre than series of conductive 'channels' that are insulated from one another by non-conductive rubber. If you disassemble these strips (by removing them from the display assembly) it makes no difference how you re-assemble them. The purpose of the strip is to carry data (digital signals) from the circuit board to the LCD display. Obviously, the signal from the PCB must be carried to the appropriate contact on the LCD display. The alignment is accomplished by positioning the PCB in an exact location under the LCD display. The position of the connecotr strip makes no difference since it acts as a conductor with MANY POSSIBLE paths to the LCD. The conductors are spaced such that they cannot "short circuit" between signal paths. As a result, the proper connection is always made between the PCB and the DISPLAY. Well, ALMOST always.

There is a problem that develops over time with these connectors. As some of the more observant posters have noticed, OLDER connectors seem to develop problems. This is because, when originally assembled, the connectors were COMPRESSED between the PCB and the LCD. Over time, the rubber loses its resiliency and tends to DEFORM (warp) and some of the conductive fibers no longer make connection. Some of the fibers may have "muckled" on to the glass connection to the LCD providing a good connection, but when the bond is broken (attempt to clean, refurbish) the connection fails upon re-assembly.

The only reliable solution to theis problem is to replace the elastomeric connector. Many reputable manufacturers provide this part at nominal cost. Others (most noatably Fluke) obfuscate the part number and availability of this $3.00 part; possibly in hopes that you will trash your otherwise excellent DMM and buy a new one (from them?).

Since the part, while used by NUMEROUS manufacturers is often available, it must be an EXACT duplicate of the original for it to function properly. The Fluke part number for this item is 817460, but Fluke refuses to admit that the part even exists. The only item they offer is a "kit" to repair your DMM that contains the strips, a new display illuminator (white rather than the OEM green) and other stuff you don't need. Cost is about $ 60.00.

I used to run the calibration laboratory at the UNH Space Science Center in Durham, NH so I know of what I speak. My motto is that "If it works, it's a Fluke". Take that any way you want.

 

[MrAl]

Hi Scott,


A little late response (he he) but nevertheless much appreciated. It's also nice to hear that someone has been around longer than i have (also ha ha).

I always suspected such because my personal experiments have always failed no matter what i did, with only one exception. That was, to build into the product a 'new' way to compress the old strip. This takes a lot of inventiveness though because we're often working inside spaces that are very small. The idea was to simply provide for more pressure between the glass and the circuit board such that the old strip gets more compressed than it was before.
With one old meter i had years ago, i had used one of those small black colored binder clips you get at stationary stores for keeping papers clipped together. The two metal wire 'handles' are removed after the clip was installed so all that was left was a binder clip body helping to keep the strip under more pressure against the glass and circuit board. It was just enough and happened to be the right size for the circuit board and the way they did it originally.

Anyway, for other meters it would probably take more inventiveness than that, perhaps installing some very small springs along the length or something.

I was looking for a better solution, but from what you say it appears that there just isnt any better when you cant get a replacement part.

 

[scottksmith]

Those pesky elastomeric cvonnectors !

Thanks for the nice comments, Al.
Just a quick note relative to the connectors on many (most) Fluke DMMs. I have had little success cleaning the strips with alcohol, but great success with tetrachloroethylene (CRC "Lectra Motive Electric Parts Cleaner" --- available from Autozone and others.) Use a saturated Q-Tip and rub well on the strip, the LCD contacts and the PCB contacts. It may get you by. If you do some homework on E-Bay there are people selling NEW strips for ALMOST reasonable money. (Check out some guy called "a-fluke" who has an E-Bay store.) I have wondered if it would be possible to simply purchase ANY strip that was the proper width and cut it to length to fit the slots under the LCD. If anyone has luck with this, please let me know.

Hi Scott,


A little late response (he he) but nevertheless much appreciated. It's also nice to hear that someone has been around longer than i have (also ha ha).

I always suspected such because my personal experiments have always failed no matter what i did, with only one exception. That was, to build into the product a 'new' way to compress the old strip. This takes a lot of inventiveness though because we're often working inside spaces that are very small. The idea was to simply provide for more pressure between the glass and the circuit board such that the old strip gets more compressed than it was before.
With one old meter i had years ago, i had used one of those small black colored binder clips you get at stationary stores for keeping papers clipped together. The two metal wire 'handles' are removed after the clip was installed so all that was left was a binder clip body helping to keep the strip under more pressure against the glass and circuit board. It was just enough and happened to be the right size for the circuit board and the way they did it originally.

Anyway, for other meters it would probably take more inventiveness than that, perhaps installing some very small springs along the length or something.

I was looking for a better solution, but from what you say it appears that there just isnt any better when you cant get a replacement part.

 

[MrAl]

Hi again Scott,

Very good question there. If a new connector strip from another type of meter (as long as it was long enough) would work in another meter with a little trimming, that would be great. All we'd have to do is find a strip that is about the same height and is at least as long as the old strip.

What i dont know is if they make the conduction bands different widths or spaced differently for different strips. I would think they would have to be similar though.

 

[OlPhart]

A Great thread... I've had good results with isopropanol, by being almost sterile in cleaning, handling & reassembly. Also used little shims under the twist tabs to add some force. Thankfully, haven't had to do any of this more than a few (<5) times.

I suspect the pitch of conductors may be standard (or few variants) in elastomeric strips, but thickness (width?) might vary more. All the types of backlighting (or not) would contribute to this. Good Stuff, TNX 2 All <<<)))

 

[MrAl]

Hi Ol,

Yeah this is another one of those cases where progress has produced a very hard to repair product and we want to find ways to do it cheap. Not easy i guess.

 

[OlPhart]

Yup, I call this the "Bic lighter" syndrome: cheap, reliable & functional Until it goes south. Then it's nigh onto impossible to fix, and as versed to cost, becomes landfill. When was the last time you saw a Zippo? sigh... <<<)))

 

[jerry1020]

elatomeric connector

I have no personal experience with these connectors but came accross a You Tube posting that mentions using salvaged ones from a dvm to repair a marine device. Search You Tube for "repairing a NavMan 3100". Hope this helps.

 

[Gordon J]

A Great thread... I've had good results with isopropanol, by being almost sterile in cleaning, handling & reassembly. Also used little shims under the twist tabs to add some force. Thankfully, haven't had to do any of this more than a few (<5) times.

I suspect the pitch of conductors may be standard (or few variants) in elastomeric strips, but thickness (width?) might vary more. All the types of backlighting (or not) would contribute to this. Good Stuff, TNX 2 All <<<)))

On the track of the little shims. I've struck this problem a few times and found cleaning everything with metho and then using a couple of bits of sticky tape on the front of the lcd screen to push it back a little gives me the extra connecting force I need.

 

[MrAl]

Hi Gordon and welcome to the forum.

Yeah these connectors are a pain to deal with. I cant believe this thread was from two years ago already. Seems like a few days ago we were talking about this.

I am lucky as i have not run into this kind of connector again yet. I hope i never do again. One of my meters is down for good because of that, but lucky it wasnt a real expensive one. I've gotten several more meters after that so i doubt i'd want to repair it now anyway though, and not sure i have all the case parts still around anyway.