The RF LEd meter may show reduced output after continuous transmission, while output actually remains constant. Changing components on the final unit will correct this problem. This change applies to units before serial number 201XXXX.

Procedure:

1. Remove the top cover (four screws), and unplug the speaker.
2. Remove the bottom cover (four screws).
3. Remove four scress holding the heatsink and swing the sink down.
4. Without changing coil spacing, desolder L6 which connects from the ANT pad aon the final unit to the PL-259, at the final unit.
5. Remove five screws holding the final unit pcb X45-1180-10, one screw holding Q6 2SD880, and two screws holding the final hybrid module Q1, M57726.
6. Change the following parts:
   
   C15 1pf to 2pf (CC45CH1H020C)
   D3 1N60 to 1S1587 (V11-0370-05)
   R8 820 ohm to 1.2K (RD14CD2E122J)
7. Insure adequate thermal compound on Q1 and Q6, and that the mica washer is correctly positioned under Q6. Reverse steps 5 and 4 to partially assemble.
8. Cable-up power and a dummy load. Readjust VR1 on the final unit at 147.000 MHz, high power setting for 5 LED's ON. Switch to low power and verify 3 LEDs ON.
9. Remove power from the unit and complete reassebly by reversing steps 3, 2, and 1.

Note: installation time for this procedure is 1/2 hour or less.



08-04-2000 Memory Channel 7 Indicator Erratic
Author: Trio-Kenwood Communication, inc.

When Memory Channel 7 is selected, the LED may fail to indicate the number 7, although frequency is correctly recalled and all other operations are normal. Cause is incorrect voltage level at Q16 & Q17, and is related to individual differences between these IC's. Correction is by changing one resistor value on the control unit.

On the control unit X53-1130-xx, replace R38 from 3.9 Kohm to a 1.8 Kohm resistor (RD14CB2E182J). No adjustments are required.

This change should be perform only as necessary, and applies to units before serial number 205xxxx.

Installation time for this procedure is ½ hour or less.



08-04-2000 TR-7800, TR-7850 Memory Improvements
Author: Trio-Kenwood Communication, inc.

TR-7800 & TR-7850 memory retention may be improved by the following changes on the control and RX units.

Control unit X53-1180-xx

1. If not already present, add a 470 Kohm ½W resistor (RD14BB2B474J) (R54) on the foil side of the board from connector 11 UP line to ground. (Unite before serial number 1119391).
2. If not already present, add a 470 Kohm ½W resistor (RD14BB2B474J) (R55) on the foil side of the board connector 11 DOWN line to ground. (Unite before serial number 1119391).
3. Hard-wire the two via holes (through hole without components leads installed) along the foil trace between Q18 pin 1 and L1.
4. Change D1 from an ZX-060 (6V, 5%) to a WZ-040 (VII-4102-40) (4V, 10%) Zener.
5. Check D3 for leakage, which would load the MB line voltage below it normal 5.2 V DC setting.

RX unit X55-1270-xx

1. TR-7800: Change R94 from 56 ohm to 150 ohm ½W (RD14CB2E151J).
2. TR-7850: Change R94 from 100 ohm to 150 ohm ½W (RD14CB2E151J).
3. Cut the foil at the input to Q27, and connect Q27 input to the BB terminal. Connector 1 for constant battery charge at Power switch Off, and floating battery charge when using a TK-1 or BC-1 charger unit for memory back-up in base station operation.
4. Check D18 for leakage, loading the MB line.

Note:

1. With 13.8V DC applied to the radio, and the power switch OFF, adjust VR2 on the RX unit for 5.2V DC at connector 1, MB terminal.
2. We recommend using either Sanyo or GE NiCad Batteries. We suggest not using Radio Shack or Eveready batteries in these radios.
3. If memory loss persists after all changes and checks suspect control unit Q18 is defective.