Adding a PL Disable Switch to the R100 Control Board

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Back to Home Adding a PL Disable Switch
to the R100 Control Board
By Robert W. Meister WA1MIK

The repeater control board has the ability to disable receiver PL for monitoring audio feeding the J3 service jack and the loudspeaker. The repeat function always requires PL if the receiver is programmed that way. This same procedure applies to, and works for, DPL if your station is configured that way. The board is silk-screened for this functionality but both of the stations I've encountered were missing the parts.

You only need the DIP switch to disable the PL; the rest of the parts are installed to give you a visual indication that you've done so.

Obtain the following parts:

Single-position DIP switch, Mouser p/n 611-BD01
NPN silicon small-signal transistor, 2N2222, 2N3904, or equivalent
1.5k 1/4 or 1/2 watt resistor or surface-mount equivalent
47k 1/4 or 1/2 watt resistor or surface-mount equivalent
T1-size amber LED

Total parts cost is under $2.00, less if you already have some of them in your junk bin. It took me under an hour to select, accumulate, and test the parts, and do the entire job.

Here's the upper-left corner (when viewed with the station mounted to a wall) showing the area without the parts.

Here's the circuit board X-ray view of that same area.

Here's the solder side of that same area.

Finally, here's the schematic showing the parts we'll be installing.

Step-by-step procedure:

Disconnect power from the station.
Unlock the front door and open it.
Disconnect the two radio cables going from the control board to the radios AT THE RADIOS. They're permanently attached to the control board.
Disconnect the power cable from the control board.
Remove 9 screws holding the control board to the cover and remove the board.
Remove the solder from the holes for the switch, LED, and transistor.
Install the switch, LED, and transistor on the component side of the board. Orient the switch such that it closes (is ON) when pushed towards the edge of the board. The transistor's collector lead goes to the hole with "C" next to it. This may be opposite of the other nearby transistors.
Install the two resistors on the solder side of the board. Make sure they stand off the circuit board and can't short out against anything. There's plenty of clearance under the board for even 1/2 watt resistors.
Reinstall and reconnect the control board and the station.
Test for proper operation. With the switch ON, the LED should light up and you should not need PL tone on the incoming signal to hear it on the service headset or loudspeaker (if installed).

Here's what that area of the control board looks like with the parts installed. Both the PL DISABLE and RPTR DISABLE switches are turned on and their respective LEDs are illuminated.

The author may be contacted at: his-callsign [ at ] comcast [ dot ] net.

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This page originally posted on Tuesday 21-Jul-2009

This web page, this web site, the information presented in and on its pages and in these modifications and conversions is © Copyrighted 1995 and (date of last update) by Kevin Custer W3KKC and multiple originating authors. All Rights Reserved, including that of paper and web publication elsewhere.