Disabling Talkback


DX 33HML
Disconnect wire located in TR30

DX 44V, DX 66V, DX 73V
Disconnect wire located in J15

DX 77HML
Disconnect wire from resistor R244

DX 88HL
Disconnect wire located in R189

DX 99V
(original type echo board) Disconnect wire located in TR35

DX 99V
(smt type echo board) Disconnect wire located in J15 next to R244

DX 11B
Disconnect wire from diode located in R244

DX 22B
Disconnect wire from diode located in R327



Talkback Mod

Talkback can become distorted if these radios have been "peaked," and there is no cure because
the talkback just amplifies what goes to the RF section. Try adding a 470k ohm resistor from junction
of C155/R207 to the junction of C187/R235 on the solder side of the board. This will also give you
clean talkback on SSB and FM. Try different values of resistance to get the amount of volume you want.
The less the resistance the louder the talkback will be.



DX 2517

Symptom:
Talkback squeals when mic gain is at max
Problem:
Excessive drive to IC-8 pin 4
Cure:
Replace R-221 with a 200K ohm resistor


Roger Beep Mods

The tone and time of the roger beep on the 10 Meter mobiles can be changed as follows:
The roger beep tone is controlled by R181 which is 220K ohms:
for a higher tone try 150K to 200K ohms
for a lower tone try 270K to 2M ohms
The roger beep time is controlled by C134 which is 2.2uF@16V DC:
for longer time try 5uF or 10uF@16V DC
for shorter time try 1uF@16V DC



Clarifier Mods
Some people have asked how to make the fine clarifier control track on transmit and receive
like the coarse clarifier control. Below are the mods for our 10 Meter SSB mobile models
(DX 77HML, DX 88HL and DX 99V) as well as the mod for the DX 2517.


10 Meter SSB Mobiles
Remove R141
Remove D38
Solder bridge J106 pin 54 to 8 volts

DX 2517
Remove D68
Remove R113
Add jumper from R113 to 8 volts

1. Remove the bottom cover to get to the PC board with the jumpers. It will be a small PC board immediately behind the front panel.

2. Locate "J2". There will be a jumper on pins P3 and P4.

3. Remove this jumper to expand coverage to 26 MHz - 29.7 MHz.

4. Move the jumper from P3-P4 to P1-P2 to expand coverage to 26 MHz - 32 MHz.

5. After moving (or removing) the jumper, press the CPU reset button (located below J2).
NOTE: Operation between 30-32MHz may require retuning the VCO.