8719-192-L2-PLCC Washington & Cobra 142 KIT INSTRUCTIONS

 

 

 

 NOTE: RADIO MUST BE IN ORIGINAL CHANNEL CONFIGURATION. ALL CHANNEL MODS MUST BE REMOVED AND COMPONENTS RETURNED TO ORIGINAL CONDITION.

 

All photo's are Zoom enabled.

 

Presteps;

Radio must have an MB8719 or equivalent PLL

 

1. Remove bottom and top covers.

 

2. Replace X4 (11.1125) with the enclosed xtal.

 

 

 

 

3. Since Pin 10 is permanently grounded, we must isolate it so we can use it. Cut the ground plane run as illustrated below.

 

4. Connect the WHITE wire from connector J3a to pin 10 of the PLL on the top of the IC.

5. Connect the RED wire from connector J3a to J5 or Pin 9 of the PLL or the empty Resistor hole as illustrated. This is the best place to pick up a clean 8 volts.

 

  

Take note of the connector labels. One pair is for the 959 style chassis (939, 949, 959, 969, 696, FD-1, 699, 2547 etc.).

The other pair is for the 979/Cobra style chassis.

 

For the Cobra type radio’s, use the connectors labeled “979/COBRA”.

The 959 connectors should not be installed on Cobra boards assembled after 8-1-09.

 

CAUTION! Connecting your radio to the wrong set of connectors could permanently damage your radio!!

 

 6. Locate the muti colored wires coming from the Channel Selector board and connecting to the main board. Make sure the colors illustrated match the colors in your radio! If not, STOP!! Contact Tech Support.

 7. Unsolder the six multi color wires shown - only, at the main board, that come from the channel selector board, to the main board.

 

 

8. Clean out these holes.

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 9. Wire connector J1a to the same color wires as shown.

Plug the loose end into J1a, (labeled 979/COBRA) on the LesComm board.

The picture below shows the wires from the channel selector properly connected to the J1a cable and heat shrink protects the solder connection. The cable can be plugged directly into the Cobra Adapter to bypass the Lescomm board and restore the radio to operation for troubleshooting purposes. But you must reground pin 10 for it to work.

 10. C142 gets in the way of the Cobra adapter connector, so we must move it to the bottom. Remove C142 and install it on the bottom of the board as shown. Then install the Cobra adapter to the main board as shown. Again, take note of the SILVER MARK. Connect the cable to J3a (labeled 979/COBRA) on the LesComm board.

 THE SILVER MARK GOES TOWARD THE OUTSIDE

 

11. For better VCO coverage, cut or remove R71. Located close to the PLL IC.

If your VCO still will not cover all the bands, replace R74 with a 100k ohm.

 

12. Using the enclosed double bracket install the bracket as shown.

 

13. Mount the LesComm board as shown below.

 

 

 14. Next replace the Mic Gain control with the Band switch. Just turn the Mic Gain up all the way and secure it behind the control panel. Make sure it is insulated from shorting out either itself or another electrical connection. install the band switch.

14a. Find a suitable location for the 10kc switch or use one of the switches already in the radio for a stealth installation.

 15. Connect to power and power up the radio. STOP. Check for full coverage. If full coverage is present, proceed to the Alignment section. If not, proceed to step 16.

 16. Place the Band switch in the D (4)  position, channel selector on channel 1.

 17. Using a digital voltmeter, measure the voltage on pin 17 of the 8719 PLL chip. (Should be approximately 4 volts.)

18. Connect a digital voltmeter to test point 1 (Cathode of D1) on the LesComm board.

 

19. Adjust VR1 to match the voltage you measured on pin 17 of the PLL, minus .5 volts.

Example; If you measured 4.65 volts on pin 17, set VR1 for 4.15 volts at TP 1.

Note: If using an MMB8719, set voltage .7 volts below pin 17.

20. Check for full coverage.

 

 

Reassemble your radio and Enjoy!

 

 

 

Alignment

 

Use the alignment locator below for adjustment locations.

Switch to Band C, channel 1, Clarifier at the 12 o'clock position.

Using a Non-Metalic tool,

In the AM mode, adjust CT for 26.9650 mhz.

Inject a stable 1000Hz tone via the microphone.

In USB mode, adjust L for 26.9660 mhz.

In LSB mode, adjust L for 26.9640 mhz.

Switch to Band A, channel 40. While measuring the voltage on pin 8 of the PLL, slowly go down in channels until this voltage becomes unstable and drops off. This is the lowest frequency the radio will cover. With the new crystal, usually around 26.175 without VCO adjustment. If needed, you can make VERY SLIGHT adjustments to get coverage at both ends of the bands. But remember, until you do the broadband mod, output power and receive sensitivity will fall off at the ends.

 

 

 

 

 

Reassemble your radio and Enjoy!

 

If you're still having problems, double-check the following;

Check that A15 is +5 volts. A15 is located close to IC1 and the regulator circuit, on the J1 side.

Ensure that RA1’s common pin is to +5 volt hole (pull up).

RA1’s common pin is denoted by a dot above the pin. 

 

 

Side Notes; Power falls off at the ends of coverage on the Uniden made radio’s more than the Ranger made units. It is possible to balance out the power from the top to the bottom, but that’s not covered here.

The RCI8719-97 is a 7 bit device, but the internals of the IC do not allow it the control of the VCO as well as a -99. If you have the RCI PLL, I recommend you replace it with an RCI8719-99 and change the crystal. You’ll be much happier with the results.

 These instructions should also apply to the 5 pin President or Uniden Madison.