Date: Thu, 1 Jun 2006 15:44:25 -0700
Reply-To: Richard Koerner <RKoerner@AVANTMEDICAL.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Richard Koerner <RKoerner@AVANTMEDICAL.COM>
Subject: Re: dashboard clock
Content-Type: text/plain; charset="us-ascii"
Raymond,
Recently my LCD dash clock "stopped working". In my case, the display
wasn't "dark"; rather, the numerals disappeared, just showing the light
silvery-green background.
Now, I've worked a lot with LCD's and there is very little to go wrong
with them; it's the connections to them that cause problems. Most
typically, the connection is made with what's called a "zebra strip",
which is a rubber strip made of ever-so-thin alternating strips of
conductive and non-conductive rubber (under a 5X jeweler's loupe you can
easily see the gray and black layers, hence the "zebra" name). This
zebra strip gets compressed between the LCD glass and the PCB; the
traces on the LCD (which are almost invisible; they are conductive
vapor-deposited metals on the glass which actually conduct very low
current electricity) and the traces on the PCB are aligned with each
other via a plastic frame. The zebra strip conducts signals between the
LCD and the PCB: this is Connection "A". Remember, this is a WHOLE
STRIP of connections, not just 1 wire, but only 1 bad connection is
enough to make your clock not function.
Also, as I recall, there is Connection "B": this is between the blue
flex-circuit on back of instrument cluster and the clock PCB. This
provides electrical power to the PCB, the "brains" of the clock.
What I did to fix my clock was remove the instrument cluster, and work
my way on the back to the clock. Going from memory, I recall removing a
couple screws holding the plastic clock housing. Sure enough, there was
a zebra strip and LCD glass inside. Using reasonable care, I removed
LCD and zebra. I gently cleaned the contacts on the LCD with rubbing
alcohol and a Q-tip; I used a little more aggressive cleaning again with
alcohol and Q-tip on the zebra strip (it's pretty bulletproof), being
very careful to leave no debris behind (here's where that 5X jeweler's
loupe really comes in handy--see McMaster Carr). And, I used alcohol
and Q-tip on the PCB followed by a light rubbing with a pencil eraser to
brighten the contacts. Did a similar cleaning between the flexcircuit
and the PCB; I think somebody in the archives suggested adding a shim to
increase the contact pressure between the PCB and the flexcircuit; I
think I used a strip off a paper business-card for my shim. Or maybe it
was a strip from a plastic, TV dinner tray (emergency rations!), I don't
remember exactly.
Anyway, instant-presto, once back together, it worked, and has been
working faithfully over the past 10 months. So, it was either corrosion
or some foreign object somewhere in the LCD/zebra/pcb/flexcircuit
"sandwich" that was my problem, and may be yours, too. By the way, I
did all the repair sitting in the driver's seat, with things on my lap.
Have all tools and cleaning materials nearby in the passenger's seat.
At the website vanagon.com, under the "problems" section, there's a very
good write-up on how to fix the clock. But our Vanagon "clocks" are
composed of a "brains section" (the electronics on the PCB) and a
"display section" (the LCD) and a "power section" (the flexcircuit), and
I think a lot of the time there's no communication because of a crummy
connection between the 3 of them, and that's probably the source of most
clock problems.
Hope I don't "have my wires crossed" on this explanation, because like I
said I'm only going from memory; but the whole episode was easy and
uneventful, and it's sure convenient to have a clock that works.
Rich
'85 GL
San Diego
-----Original Message-----
From: Raymond Paquette [mailto:raymondpaquette@GMAIL.COM]
Sent: Thursday, June 01, 2006 12:18 PM
To: vanagon@GERRY.VANAGON.COM
Subject: dashboard clock
Anyone have suggestions for fixing the digital clock on my dash
cluster? It's just gone dark.
Raymond
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