Has anyone here had experience cleaning the push button keypad on a scanner?
My 15 year old Radioshack Pro-51 works fine, except that I have to press
harder than normal on the keys to get the scanner to operate. I haven't
opened it up yet, but the keypad may be the conductive type that connects
with contacts on a PC board. Does that sound right, and can the keys or PC
board be cleaned? Thanks ahead of time.
-N.Morrow

Meat Plow wrote in message ...
On Thu, 18 Feb 2010 12:22:53 -0800, "N.Morrow" wrote:

Has anyone here had experience cleaning the push button keypad on a
scanner?
My 15 year old Radioshack Pro-51 works fine, except that I have to press
harder than normal on the keys to get the scanner to operate. I haven't
opened it up yet, but the keypad may be the conductive type that connects
with contacts on a PC board. Does that sound right, and can the keys or PC
board be cleaned? Thanks ahead of time.
-N.Morrow


Probably bubble type and not cleanable.

If it *is* a keymat type employing conductive rubber 'lozenges' and either
gold plated print or chemically deposited carbon contacts, as are often used
in telephone and remote control keypads, then these can usually - although
by all means not always - be recovered using 99.7% or better electronics
grade isopropyl alcohol, and a cotton bud (leftpondian Q-Tip).

You will usually find a 'gummy' deposit on the keys that are struggling to
work. This appears to be a product of the conductive rubber breaking down.
In very stubborn cases, I have effected total recovery, by taking a keymat
from a scrap remote control, and carefully razor blading some lozenges off
the backs of the rubber buttons. The bad ones that you are replacing can be
similarly bladed off, and your recovered replacements superglued back onto
the keymat that you are repairing. Obviously, this is a bit of a 'make or
break' operation, and needs a degree of skill to accomplish successfully,
but if you are committed, and take your time, it's not terrifically hard to
do.

Arfa

On Thu, 18 Feb 2010 12:22:53 -0800, "N.Morrow" wrote:

Has anyone here had experience cleaning the push button keypad on a scanner?
My 15 year old Radioshack Pro-51 works fine, except that I have to press
harder than normal on the keys to get the scanner to operate. I haven't
opened it up yet, but the keypad may be the conductive type that connects
with contacts on a PC board. Does that sound right, and can the keys or PC
board be cleaned? Thanks ahead of time.
-N.Morrow

I haven't worked on that particular model but plenty of experience
dealing with RS, Uniden, GRE, etc. Your keyboard problem is typical
and can be cleaned if you can get it apart.
http://support.radioshack.com/support_electronics/7508.htm
http://wiki.radioreference.com/index.php/Pro-51
The problem is that the keyboard is buried UNDER all the electronics.
You have to literally rip out everything to get to the keyboard. If
you've never done this before, take lots of digital pictures as you go
along.

Looking at the exploded view, it appears to be a rubber keyboard.
Disassembly doesn't look too horrible:
http://support.radioshack.com/support_electronics/doc10/10772.htm
I use household cleaner, such as 409 or Fantastic. Alcohol might
work, but watch out for solvents that remove the silk screening from
the key tops. Don't use aggressive solvents as they're sure to wreck
something.

You'll probably find considerable filth around the buttons and in the
holes in the plastic case. Clean with a q-tip or brush.

You'll also need to clean the keyboard PCB pads. These are usually
gold traces, with silk screen graphite contacts. Wet, smear, and rub
VERY lightly. You don't want to scrape off the graphite. Solvents
are also a bad idea here.

I noticed that the PRO-51 has the evil square sealed pots for vol and
squelch. They're are another headache waiting to happen. If you're
getting scratchy sounds when adjusting the controls, dead spots, or
erratic operation, it's time to clean these. The problem is that
there's no place to inject contact cleaner into these pots. I had to
drill a tiny hole in the side and inject oil and solvent with a
syringe. Bug me if you want to attempt this and I'll disassemble and
photograph one that worked (some did not).


--
# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
# 831-336-2558
# http://802.11junk.com
# http://www.LearnByDestroying.com AE6KS

Jeff Liebermann wrote:
On Thu, 18 Feb 2010 12:22:53 -0800, "N.Morrow" wrote:

Has anyone here had experience cleaning the push button keypad on a scanner?
My 15 year old Radioshack Pro-51 works fine, except that I have to press
harder than normal on the keys to get the scanner to operate. I haven't
opened it up yet, but the keypad may be the conductive type that connects
with contacts on a PC board. Does that sound right, and can the keys or PC
board be cleaned? Thanks ahead of time.
-N.Morrow

I haven't worked on that particular model but plenty of experience
dealing with RS, Uniden, GRE, etc. Your keyboard problem is typical
and can be cleaned if you can get it apart.
http://support.radioshack.com/support_electronics/7508.htm
http://wiki.radioreference.com/index.php/Pro-51
The problem is that the keyboard is buried UNDER all the electronics.
You have to literally rip out everything to get to the keyboard. If
you've never done this before, take lots of digital pictures as you go
along.

Looking at the exploded view, it appears to be a rubber keyboard.
Disassembly doesn't look too horrible:
http://support.radioshack.com/support_electronics/doc10/10772.htm
I use household cleaner, such as 409 or Fantastic. Alcohol might
work, but watch out for solvents that remove the silk screening from
the key tops. Don't use aggressive solvents as they're sure to wreck
something.

You'll probably find considerable filth around the buttons and in the
holes in the plastic case. Clean with a q-tip or brush.

You'll also need to clean the keyboard PCB pads. These are usually
gold traces, with silk screen graphite contacts. Wet, smear, and rub
VERY lightly. You don't want to scrape off the graphite. Solvents
are also a bad idea here.

I noticed that the PRO-51 has the evil square sealed pots for vol and
squelch. They're are another headache waiting to happen. If you're
getting scratchy sounds when adjusting the controls, dead spots, or
erratic operation, it's time to clean these. The problem is that
there's no place to inject contact cleaner into these pots. I had to
drill a tiny hole in the side and inject oil and solvent with a
syringe. Bug me if you want to attempt this and I'll disassemble and
photograph one that worked (some did not).


With all sorts of conductive rubber button keys, I have had good results
with dry wiping the bottom of each contact pad of the rubber key mat on
plain unused copier paper. You need to use enough pressure to leave a
carbon mark on the paper and keep it square for even cleaning. You only
need to 'streak' each pad an inch or so as the layer of reduced
conductivity or contamination is very thin. Take care not to rip the
mat. Its usual to be able to restore a dead or nearly dead button to
normal operation as long as the button isn't physically damaged.

If the mat is very dirty, get as much loose 'spooge' off as possible
with dry tissue then wash with hot water and a trace of dish detergent,
rinse and dry thoroughly before cleaning the pads as above.

Plated contacts on the PCB are easy, but the carbon contacts and tracks
come off if you look at them wrong as mentioned by Jeff above.

--
Ian Malcolm. London, ENGLAND. (NEWSGROUP REPLY PREFERRED)
ianm[at]the[dash]malcolms[dot]freeserve[dot]co[dot]uk
[at]=@, [dash]=- & [dot]=. *Warning* HTML & 32K emails -- NUL:

On Fri, 19 Feb 2010 06:24:47 +0000, IanM
wrote:

With all sorts of conductive rubber button keys, I have had good results
with dry wiping the bottom of each contact pad of the rubber key mat on
plain unused copier paper. You need to use enough pressure to leave a
carbon mark on the paper and keep it square for even cleaning. You only
need to 'streak' each pad an inch or so as the layer of reduced
conductivity or contamination is very thin. Take care not to rip the
mat. Its usual to be able to restore a dead or nearly dead button to
normal operation as long as the button isn't physically damaged.

That's the way I used to do it. It works fine for large carbon button
areas, but gives me grief with small diameter buttons. The small
carbon button tips seem to have less adhesion. Rub them hard enough
and they will break off chunks around the edges.

I've also experimented trying to determine if the connection problem
is in the button side, or on the PCB contacts. Although the button
may look rough and in need of cleaning, it's the crud on the PCB that
really is causing the problem. What seems to be happening is that the
rubberized buttons are sweating some kind of oily goo that keeps it
flexible onto the PCB contacts. Small pieces of carbon also fall off
the rubber buttons, mix with the oily goo, and build up a mound on the
contact area. Once the mound has become high enough, there's not
enough carbon surface area left to make a decent connection unless
substantial pressure is applied. I've found that cleaning the PCB is
usually sufficient, but since I'm inside the keyboard, might was well
clean off the loose crud from the rubber buttons anyway.

If the mat is very dirty, get as much loose 'spooge' off as possible
with dry tissue then wash with hot water and a trace of dish detergent,
rinse and dry thoroughly before cleaning the pads as above.

Not dry tissue. Use something that doesn't leave lint all over the
PCB, such as a dry cotton cloth (t-shirt rags). As for cleaner,
almost anything that removes the oily goo will suffice.

Plated contacts on the PCB are easy, but the carbon contacts and tracks
come off if you look at them wrong as mentioned by Jeff above.

Yep.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558