Zebra Strip Contact Reliability

No solution other than to repeat cleaning that I know. Some configurations are more susceptible. I just recently cleaned a Fluke

77 display that worked for 20 years that developed a segment that had less contrast than the others.

I have no personal experience with using them, but one of the 3M "Electrically Conductive Adhesive Transfer Tapes" might be just the ticket here. There are several variations available, differing in adhesives and other properties, but something like #9705 or #9706 sounds as though it may be appropriate and reasonably easy to work with in the usual repair shop conditions (e.g. not requiring baking or high pressures to bond).

These are double-stick tapes that conduct in the Z axis (through the tape) but insulate in the X and Y axes. Really cool sounding, but possibly rather spendy; I haven't checked prices or availability. They also have some similar tapes that are "XYZ Isotropic" and conduct in all directions.

I've no idea if other companies offer similar products.

--
Andrew Erickson

"He is no fool who gives what he cannot keep to gain that which he cannot
lose."  -- Jim Elliot

Sometimes, figuring a way to very slightly increase the compressive force will help in a marginal situation.

-- sam | Sci.Electronics.Repair FAQ:

Repair | Main Table of Contents:

+Lasers | Sam's Laser FAQ: | Mirror Sites:

Important: Anything sent to the email address in the message header above is ignored unless my full name AND either lasers or electronics is included in the subject line. Or, you can contact me via the Feedback Form in the FAQs.

How 'bout an appropriately sized length of shrink wrap?

Meant heat shrink tubing.

Nooo... you don't want anything that is electrically conductive contacting either the Zebra strip or the display or the PCB. To do so would short the individual conductive segments, which must remain isolated from each other!!!! I've no experience with the double-stick tapes mentioned above, but it's hard to envision that as a solution to this problem. Might work, but I'd need it proven to me before I could recommend it. As was previously suggested, the only repair for this problem is cleanliness and, if necessary, more pressure.

--
Dave M
MasonDG44 at comcast dot net  (Just substitute the appropriate characters in the 
address)

Life is like a roll of toilet paper; the closer it gets to the end, the faster 
it goes.

I cleaned my Fluke for the second time, scrubbing the PCB contacts thoroughly with alcohol. I was about to ask the group if anyone knew of a safe way to clean the zebra contacts. (The very first cleaning needed in nearly 20 years occurred four or five months ago.)

Any chance of coating the stripes with the conductive paint used for automobile window heater strips. That would provide a new conductive surface, and would be a bit thicker so that there would/should be more pressure on the contact point.

Bob Hofmann

I was going to mention that but it can be a difficult to do and could actually do some damage if your not careful. I recall doing just that on a Yaesu ham radio moblie display that would lose segments from vibration. I purchased a replacement and sold the radio. I later found that this was a common problem for that particular unit and Yaesu/Vertex Standard had corrected it in their replacement display.

I have this problem on a car radio LCD display, when I get round to it I am going to try something that we used to do on old TV turret tuners - the contacts were silver plated and needed cleaning fairly regularly. However, if after cleaning a VERY thin smear of vaseline was applied to the contacts it was rare to have to clean them again. You may think that the vaseline would insulate rather than improve contact, but the light pressure of the leaf contact was enough to push the vaseline aside. Vaseline is self healing so prevents oxidation. I have used it successfully in remote control handset contacts, pots in guitars and amps and even the home telephone. I would stress that the smear of vaseline we are talking about here is just that - a very light smear so as to almost be invisible. Wether or not it will work on non-moving contacts remains to be seen.

Roy the Old Tech

Single zebra strip has 4 possible re-orientations , 2 strips have 32 orientations/swaps. That plus cleaning (i use methylated spirit) is usually all thats needed. Failing that, a pair of small strips of soft plastic against the viewing face of LCD to compress a bit more.

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

Any chance of coating the stripes with the conductive paint used for automobile window heater strips. That would provide a new conductive surface, and would be a bit thicker so that there would/should be more pressure on the contact point.

Bob Hofmann

precisely wrong advice, we are talking about zebra strip here, the point of it is exact alignment, between pcb pads and LCD lands, is not required

I wonder who dreamt up the concept ?

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

a

of

afterthought , I suppose you meant conductive paint added to the pcb pads (stripes), not the zebra (stripes)

A shmeer, eh?

Vaseline isn't very conductive. Without any wiping action, it's likely simply to plug up the works on non-moving contacts.

"William Sommerwerck" wrote in news:Gp6dnTyJE7oNdm7VnZ2dnUVZ snipped-for-privacy@comcast.com:

I wonder if Deoxit or cramolin would help?

--
Jim Yanik
jyanik
at
kua.net

"N Cook" wrote in news:gd1j07$9ea$ snipped-for-privacy@inews.gazeta.pl:

why not use gold leaf on the PCB pads,build up thickness(increasing contact pressure)? conductive paint will be soft and contact pressure will force it aside and possibly short out adjoining pads.

--
Jim Yanik
jyanik
at
kua.net

Maybe I wasn't clear enough in my explanation, but these tapes are only conductive unidirectionally, rather like a zebra strip actually. They insulate across the X and Y axes, but conduct through the Z axis, so adjacent pads (assuming they appropriate separation, etc.) are still insulated from each other.

The "XYZ Isotropic" tapes are different and obviously unsuitable for the application, since they don't insulate; however, the others should work to some degree, at least in theory.

--
Andrew Erickson

"He is no fool who gives what he cannot keep to gain that which he cannot
lose."  -- Jim Elliot

Great idea. Then you can buy a new radio.

--
http://improve-usenet.org/index.html

aioe.org, Goggle Groups, and Web TV users must request to be white
listed, or I will not see your messages.

If you have broadband, your ISP may have a NNTP news server included in
your account: http://www.usenettools.net/ISP.htm


There are two kinds of people on this earth:
The crazy, and the insane.
The first sign of insanity is denying that you\'re crazy.