Pro-51 scanner radio keyboard repair?

[N.Morrow]

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

 

[IanM]

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.