Rotary Brake Pot Installation for
"Silver Series" - PMTR2039 / 2040 / 2041
Tools & supplies you will need
- pencil type soldering iron with small tip, lighter fluid, Q-tips or similar
cotton swabs, 60-40 rosin core solder, Dremel or equivalent rotary tool,
5/16" nut driver / socket, 1/16" Allen wrench, step type drill bit or
single ¼" drill bit, drill motor and small hobby knife of countersink tool
(for deburring)
Important notes - It is
important that any solder flux residue is removed after soldering with a cotton
swab and lighter fluid to prevent corrosion of the circuit board and resulting
damage from short circuits. For the same reason, acid core solder and acid flux
should never be used on this or any other soldering operation on the circuit
board. For best results follow these steps in the sequence that follows.
Step 1 - With an abrasive cutoff
disc in a Dremel (or equivalent), cut the circuit board traces in positions #1
and #2 as shown to the right on the back side of the circuit board. The entire
copper trace (area between the black lines) should be removed, so it is
necessary to cut slightly beyond the areas shown on the circuit board. Proper
types of Dremel cuts are shown in the picture below right.
Step 2 - Using a step drill or
single ¼" drill bit open up the mounting hole in #3 to a full ¼" and
debur the drilled hole to remove copper flash by using a small hobby knife or
deburring tool
Step 3 - Stand up the circuit
breaker on the 2nd picture at right and repeat the 2 Dremel cuts on the front
side of the board as shown in the same corresponding positions as the cuts made
on the back side of the circuit board.
Step 4 - After the cuts are made
unsolder the top leg of the circuit breaker (use "Solder Wick" or slot
car braid with liquid rosin flux, and reposition the top leg to the horizontal
hole indicated as #4. Because the hole at #4 is very close to the adjacent
copper trace on some circuit boards, it is recommended that the circuit breaker
leg be soldered only on the backside of the board at #4.
Step 5 - Bend the 2 outside
terminals of the brake pot to flat or 90° from their original position. Cut off
the right hand terminal close to the body of the pot and using a Dremel or
diagonal cutter trim the left hand terminal to a point as shown.
Step 6 - Insert the pot into the
front side of the circuit board with the center terminal of the pot inserted
through the hole as shown using one of the red fiber insulating washers on each
side of the board, and add the lock washer & nut.
Step 7 - Bend down the remaining
pointed terminal so that it contacts the gold plated connecting hole at #5 as
shown above. Twist the pot slightly to line up the connection and trim the
terminal if needed so that the pot will sit flat. Tighten the nut to secure the
pot. Solder the center pot terminal on the backside of the circuit board and the
pointed terminal on the front side of the board. When all of that is complete it
should appear as shown below.
Step 8 - Using cotton swabs and
lighter fluid, clean off all solder flux residue from soldering operations on
both sides of the circuit board. As noted above, take your time and do this as
thoroughly as possible.
Step 9 - Re-assemble the
controller handles and install the knob on the shaft using the Allen wrench.
Suggested setup for easy reference - position the knob so that the white line is
straight "up" when the brakes are "full" (fully clockwise
position looking at the back side of the controller).
After all is complete, test the system carefully by
installing the black and white leads first & then briefly touching the red
lead to make sure that no sparks are generated.