Lazer Tag Fast-Fire Modification

Note: I wrote the following in 1988. Please don't ask me for further details. I won't remember :)
Here is a description and schematic of the fastfire module.

**Instructions for installing a fast-fire module in a a Lazer Tag pistol**
by John H. DuBois III (

1) Open the pistol.

a) Removing the top cover:
Remove the lamp cover near the front bottom of the pistol.
Remove the screw that is at the top of the compartment, which holds the
top cover of the pistol on.  
It may be glued in and require some force to free.
It may be necessary to remove the bulb to easily access the screw.
Remove the top cover of the pistol by pressing in at the sides and lifting up.  
The cover will be held down by two tabs on its top portion.  
Slide a thin screwdriver between the cover and the gunsight and pry it away
on each side.  The cover should then be free to pop off.

b) Removing the side cover:
Remove the battery compartment cover and take out the batteries.
Slit the battery installation guide sticker in the compartment down the 
middle, along the space between the two cover pieces.
Remove all of the small screws that are on one side of the pistol.
Remove the three screws in the gunsight that hold the sides together.
Remove the screw near the front of the pistol above the circuit board.
Remove the gunsight adjustment cover that is atop the gunsight about 2/3
of the way forward.
The sides will now come apart.  
Turn the pistol over so that the screw side is down and carefully remove the
half that is now on top.
Be careful when doing this; there are several components that are likely to
fall out.
These include the sighting window, the targeting reflector, the targeting
reflector O-ring, the beam collimating lens, the trigger, and the trigger
spring.  The trigger spring in particular will probably pop out when the
side cover is removed; watch where it goes!
In case some parts fall out:
The sighting window is a small circular piece of clear plastic, about 5mm
diameter.  It fits in the gunsight near the rear of the pistol.
The targeting reflector is a small circular piece of clear plastic in a
black ring, with a small tab sticking out.  On one side, a ring of plastic
sticks out further.  Its O-ring is a small round rubber ring.  The O-ring
fits over the ring of plastic that sticks out from the reflector.  The
assembly fits in the gunsight about 2/3 of the way to the front of the
gunsight.  The O-ring side goes to the rear of the pistol.  The tab goes
toward the bottom of the pistol, and fits in a notch in the gunsight.
The beam collimating lens is a larger piece of clear plastic, curved in
on one side and out on the other (concave-convex).  It fits near the very
front of the pistol, with the side that curves out to the front of the pistol.
The trigger and spring fit in the pistol grip.  Their reinstallation is
described later.
2) Install the fastfire module.

a) Place the module in the pistol.
The fastfire module fits in the pistol grip.  Near the bottom of the pistol
grip, there is a large bypass capacitor stuck to a piece of adhesive foam.
Pull the capacitor off of the foam.  The negative lead is connected to a black
wire that goes up to the battery compartment.  The connection between the 
capacitor and the wire may be covered by insulating tubing.  If so, pull the
tubing up the wire so that the soldered junction is revealed.  Stick the
capacitor back to the foam as near to the bottom of the grip as possible,
with the negative lead up so that it can be soldered to.  Now, stick the
fastfire module onto the foam just above the capacitor, so that there is room
to work with the trigger switch.

b) Connect the fastfire module.
The fastfire module has four leads: positive supply, negative supply, trigger
input, and output.
The negative supply lead is a short black wire.  Wrap the stripped end around
the junction of the bypass capacitor lead and the wire it is connected to,
so that when it is resoldered they will not come apart.  Solder the lead on.
The positive supply lead is a short red wire.  It is to be soldered to the
positive supply contact of the trigger switch.  The trigger switch consists
of three long narrow pieces of metal just below where the trigger was.
The positive supply is a different contact on different versions of the pistol.
It is whichever contact the positive lead of the bypass capacitor is soldered
to.  Thoroughly wet the module's positive supply lead with solder.
Then, hold it against the part of the positive supply trigger switch contact
that the capacitor lead is soldered to, and solder it on.  In some pistols 
the capacitor lead will have a tendency to come off; in that case you must
hold them both on.
The trigger input lead is the third short wire, of whatever color.
It is to be soldered to the trigger switch sighting LED contact.  This is
also a different contact on different pistol versions.  It is one of the two
*top* contacts, whichever one is *not* the positive supply contact.
Solder the module lead to it by the same technique used for the positive
supply lead.
NOTE: if you are installing a fastfire/normal switch, modify the following
instructions with the instructions in section 4.
The output lead is the long wire.  It is to be connected to pin 13 of U3 on
the pistol's circuit board.  Since the fastfire module generates a reset pulse
in place of the pulse from the sound generator on the board, the source of the
original reset pulse must be disconnected.  This is done by removing C9, which
couples the reset pulse to U3.  U3 is the middle IC on the board.  C9 is close
to it, on the side toward the rear of the pistol.  Desolder and remove it.
Find the pad for C9 which is connected via a trace to pin 13 of U3.
Drill out the hole in the pad with a #60 bit, so that the stripped end of the
module output lead will fit into it.  
Before soldering it, fit the lead in along the other wires from
the pistol grip to the upper portion of the pistol.  In some pistols, the wires
are twisted together into a bundle.  In these pistols, remove the bundle from
the trough, place the output lead in, and put the bundle back in on top of it.
In others, there is some adhesive at at least one point in the trough.  Stick
the lead into it to hold it down.
Route the lead around the battery compartment contacts and up to the bottom of
the board.  Feed the stripped end of the output lead up into the drilled out
hole from the bottom, leaving enough bare wire to solder it on the bottom.
Solder it on.  Connection is now complete.  
If you have a variable power supply, adjust it to 9V and connect it to the
battery contact springs.  The positive contact has a red wire soldered to it;
the negative contact has a black wire soldered to it.  Fire the pistol by
pressing down on the top trigger contact until it contacts first the middle
contact and then the bottom contact.  Check the pistol and module for correct
operation.  If it does not work, check your wiring and soldering.
3) Reassemble the pistol.
Make sure that all of the optical elements which can fall out are in their
correct places.
Make sure that all of the wires are positioned so that they will not prevent
the pistol shell halves from fitting together.
Place the trigger back in the trigger compartment, with it fully forward.
Place one end of the trigger spring over the post on the rear of the trigger,
and compress it so that the other end fits into the trigger compartment.
The trigger-spring assembly may have a tendency to pop out.  In this case, it
must be held down while the shell is reassembled.
Place the other half of the shell onto the first half and fit it on.
Turn the pistol over.  Place the screws back in and screw the halves together.
Put the batteries in and put the battery compartment cover back on.  Check
the gun for correct operation.  If you use the sight, check it for alignment,
since disassembly and reassembly of the pistol and cause it to become
misaligned.  If it is not correct, use the two small screws on either side of
the targeting reflector on the gunsight to realign it.  Identical rotation
of the screws will move the LED sighting dot up and down; differential rotation
will move it left and right.
Put the targeting reflector cover back on.
Put the top pistol cover back on.  Snap the top tabs into position.
Put the top cover screw (in the bulb compartment) back in.  Replace the bulb if
it was removed.  Put the bulb compartment cover back on.
The pistol is now ready for operation.
4) Installing a fastfire/normal switch.
If a switch is to be installed, do not completely remove C9.  Desolder and
remove only the lead that is connected to pin 13 of U3.
Place the switch as desired.  It can be glued onto the side of the interior
of the bulb compartment if the bulb is permanently removed.
Solder a wire to the center contact of the switch, and solder its other end 
into the drilled-out pad on the board that is connected to pin 13 of U3.
Solder a wire to the free lead of C9, and tape up the junction.  Solder the
other end to one of the other contacts of the switch.
Solder the output lead of the module to the third contact.
The switch will now select between reset modes.
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This web page maintained by John DuBois