Tiny little Blaupunkt replacment switches WORK!!

[Audial <Audial@aol.com>]

What you need:

1) A Blaupunkt head unit from an '86 5KCSTQ with bad 5 station preset switches
and a bad AM/FM switch...
2) A small soldering iron, solder sucker, a couple of paper clips (one large,
one small),  and a "helping hand" attachment.
3) 8 (or if you are slightly clumsy, like me, 12 just to be careful) of the
following switches:

Catalog # FSM - 7 miniature PC mount tactile pushbutton switches.
These have a plunger height of 0.244", rated 50mA @ 12VDC.  They are 4 for
$1.00 from All Electronics Corp., 1-800-826-5432

4) Some patience

First off, these switches are not original Blaupunkt switches.  They seem to
be very well made though, and the website promises 50,000 presses. 

First, to desolder the old switches:

Remove the radio.  If you take the side covers off of the center console you
will see that the radio is held in place by two clips that can be defeated by
inserting a thin piece of stiff wire on either side.  The head unit slides
right out.  Disconnect the connectors, noting where they go in case the legend
on the top rear of your head unit has peeled off.

Remove the ON/OFF volume knob by pulling gently.  Take off the BASS and TREBLE
knobs by gently prying at the base and pulling.  They will slide off with a
little more effort.

Remove the faceplate:  Look at the sides of the radio.  The faceplate is held
on with two latches.  Insert a small screwdriver and pull gently.  As you
remove the faceplate, the trim piece for the switches that allows you to press
them will fall out of the faceplate.  It is a rubber cut-out with six plastic
inserts that contact the switches.  Don't lose it, break it, etc.

The PCB that holds the preset switches is held gently in place by two plastic
barbs.  Press their halves together and gently lift the PCB away from the head
unit.  You will see that you can't move it too far, because the wires are
short and soldered onto the face of the PCB.  This is the biggest headache.
In order to desolder the switches, you will have to find a way to keep the PCB
about 1/2" out in order to get the soldering iron in there to desolder the
switches.  I used a strategically placed packing peanut.

Desolder the switches one at a time.  Use an x-acto knife or other suitable
tool to pry the switch away from the PCB as you heat the leads.  If your
switches were like mine, they will partially disintegrate on you as you do
this.  Don't worry.  Just get the leads out of the board.  Don't scratch the
traces on the PCB.  Then make sure the holes for the switch leads are clean.
I used a solder sucker and a paperclip end to make sure there was visible
light through all 12 holes.

Now: headache #2:

The replacement switches have four leads, not two.  However, you will note
that they are connected in pairs.  I just folded the two leads on each side of
the switch flat against the bottom of the switch, so that they overlapped each
other, making it very compact.  Then I soldered a "locating lead" onto one
side of the switch as follows:

Attempted ASCII art:

                
                | |       < -- Plunger
               -----
               [   ]     < -- Switch body
                |  |      <-- Same-pole leads (fold these towards each other)

This gives this (approximately):

               | |
              -----
              [   ]
               ~~     

Then, you will note that the FSM-7 switch has an extra, fifth ground lead.  I
snipped this off and soldered it to the folded leads on one side of the
switch, then bent it parallel to the switch plunger to provide a "locating
pin":

(View of the bottom of the switch)

                                                              ___
Snipped off ground lead resoldered  --->  ---{   }   <--bent-together leads of
switch.
bend this parallel to plunger                      -----

So, now you've got a switch that initially had four leads that now has two -
one that is a locating pin. Soldering these back in is a snap.  Put the
"locating pin" into one of the holes for each switch (it doesn't matter which
one).  Lightly solder it in place.  Then you will notice that the opposite
side folded-down leads are directly over the other hole in the PCB.  Place a
little blob of solder in there to fully cement the switch to the board.

Test each switch with an ohmmeter to make sure they're working right.  All six
of mine did on the first try, which took me about 2-1/2 hours from start to
finish, including figuring out the bending/soldering rigarimole.

Take your time...

Now, for the final fit:

If you notice that some of the ends of the switch plungers stick out slightly
farther, or are slightly misaligned, don't worry.  Trial fit the faceplate to
the radio with the plastic/rubber switch cover and see if all of the switches
work freely.  If they don't, it's likely that some of them are mounted a
little too high.  Don't panic...remove the faceplate and take out the rubber
switch cover.  You'll notice that right down the center of each little square
is a hard plastic rib.  You can shave a little clearance off of this rib with
an x-acto knife gently to "custom fit" each switch.  Take off 1/32nd of an
inch at a time and trial fit it again until each switch works perfectly.  The
FSM-7s are very close to the installed height of the old switches, but because
this procedure is a little haphazard, you'll find that each switch winds up
just a teeny bit off.

Approximate time for switch replacement procedure, radio-out to radio-in (all
6):  3 hours.
Cost (assuming you have basic soldering tools): about 5 bucks.

Do they work?  Well, mine work and feel great, and are virtually
indistinguishable from the originals.   

I admit that it would be easier to get the original, two-lead Blaupunkt
switches for this operation.  However, maybe they are less reliable.  I also
haven't checked about the price/availability of them.  The switches I used can
be had cheaply, in quantity.  If you've ever put together a detailed model
quasi-successfully, you can perform this procedure.

BTW, the All Electronics catalog that you'll get with the switches has plenty
of other interesting stuff inside...

Best Wishes,
Alex