Magnum Delta Force, Magnum 357DX Mods

Channel expansion Version 1

Turn off the radio.

Pull the channel knob off and behind it there is a diode covered in (usually) a yellow protective isolation tube.

Cut one leg of the diode.

Turn the radio back on.

Press Func then press and hold the Call button for a few seconds.

If the diode is not behind the channel knob it will be behind the board inside the radio in the same area, it is the only regular looking part , the rest will be those little surface mount chips.

Channel expansion Version 2


This mod was sent to me by Douglas E. Roberts, thank you.

Here is the proper channel Mod. for the Magnum Delta Force that I did and it works!

Ok now soldering skills need to be very good on this job or radio will be trash.

1.Turn on power for a minimum 10 seconds then shut off and disconnect power

2.Remover cover (Speaker side).

3.Remover channel knob and locate D-555 diode which is the only thing behind knob.

4.Locate and remover 0-ohm resistor marked "000" (this resistor is a surface mount).

5.Locate and short out the CPU reset pads locate below and just to left of resistor 000.

6.Resistor and CPU pads are located on visible corner of front panel circuit board by frequency control switch.

7.Button back up and power it up.

8.Push Function and then push and hold Call for about 3 to 4 seconds and you'll be into 11 Meters

Now this Mod worked real good and you'll be able to switch bands by using the call button, it goes from A-J and frequency range from as low 25.165 at A to as high as 29.695 on J (11 Meter Band is on E), you'll need to push Function and Call each time you turn it on because it returns to defalt 28.000 MHz but it does remember the last channel you were on shown as frequency in the 11 Meter band


Channel expansion Version 3

This was sent to me by Butch, thank you.


Mods for 2001 Magnum Delta Force New Version

In this Version they have moved the Diode and two tabs to reset the memory.

They are now found on a tiny PC Board hung in the left rear of the radio.

Turn off the radio, disconnect from all power.

Remover cover (Speaker Side)

Remove the Black shorting clip from the back two pins, then press the reset button for a couple of seconds.. Sometimes it doesn’t reset properly (default of the button) So you may need to press it a few times .


Hook the radio back to power and ant.

Turn on… Press "Func" button the press and hold "Call" button untill you see the band indicated as "E" it will show a channel number like 01,02,03 etc then a E5 to the right. You will have to do this each time "Func----Call" because the radio will return to the 10 meter band when shut off.

Clarifier Mods

Before you do this mod, makes sure all the wires in your radio are the same colors as described below. Sometimes things are changed and that can make things a bit hairy.

The wire most concerned with is the clarifier on the front panel..

With the radio open and looking down at it, the clarifier is on the left. The top wire should be Gray. This is the wire involved in step 7. Mine was Gray and on the top (closest to you) looking down at the radio.

1. Turn off the radio and disconnect from power.
2. Remove D176 (on the pc board almost directly behind the clarifier)
3. Remove R244 (located right of the diode there is one resistor in between them) Save this resistor 1.5K ¼ Watt
4. Remove R306 1K ¼ watt and replace it with a jumper wire.
5. Cut or unsolder and pull from the pc board the leg of RV108 closest to R244
6. Install the resistor removed in step 3 (1.5K ¼ watt). Put the radio face toward you with the solder side of the main pc board up. Find the R244 pad closest to the front of the radio. Follow the trace to the pin (white edge connector). Solder one side of the resistor to this pin. Count over 2 pins to the right this should be +8Vdc. Solder the other end of the resistor here. (careful not to short the +8v to the surrounding traces).
7. Turn the radio over and locate the "Gray" wire on the clarifier potentiometer follow this wire to the 12 pin connector on the pc board and cut it there. Connect the gray wire to the junction of RV108 and D176 through the hole where D176 was removed.
8. Put the clarifier control in the 12 o’clock position, or centered and adjust RV108 for center frequency.

This will unlock the clarifier so it slides both transmit and receive.


Deltaforce Variable power range modification

Derek Lindberg sent me this mod, thank you.

I have a new mod for the Magnum Delta Force, so here it is.

With the bottom cover off look for varible power control knob.

On the outer legs between the top and middle legs you will find a 2.2k resistor remove it.

This will give you a greater value between high and low power.

I have done this and it works great.

This mod was for the Magnum 357DX, but it should also work for the Deltaforce.

Basic expansion

The most common and simplest conversion is cutting the diode lead on the front panel CPU PC board.

You can see the diode location in the photo below.

After the diode is cut and before the power is applied to the radio, short out the two Reset Pads illustrated in the photo below.

The conversion is now complete.


To toggle to 10 & 11-Meter operation, momentarily press the CLAR/FUNC control, then hold the CALL button for 3 seconds and release, this will be required each time the radio is powered on until an 11-Meter frequency is programmed into memory.

The above diode conversion retains the three position STEP command in the 10-Meter only band, each time the step button is pressed, one of the digits on the LCD frequency display right of the decimal point flashes.

Either the UP/DOWN buttons on the microphone or the frequency selector on the front panel will change the digit from 0-9, only that digit will change under this command.

The next digit to the left will remain unchanged while in this mode.

The operator can select and change the 1KHz, 10KHz, or the 100KHz digit while it is flashing.

To exit the STEP command simply press the step button until there are no flashing digits or momentarily press the microphone PTT switch.

Full coverage expansion

The second conversion is the full coverage conversion.

The down side to this conversion is that the radio can't be toggled back to the 10-Meter only operation and none of the commands associated with this operation can be accessed.

The up side is the radio powers on with the last frequency used without the addition steps required in the first conversion you must decide which is best for your needs.

To perform the full coverage conversion a resistor must be added to the circuit traces shown in the photo below.

The diode need not be cut, but if it is already, it won't have any effect on this conversion.

The spacing of the pads are for a SMT 1/10 watt resistor the value required for this conversion is 47KOhms, good soldering skills are needed to perform this modification, the pads are delicate and will lift off the board with excessive heat so a low wattage small tipped iron is essential, if you choose to use a standard resistor, a 47K 1/8 Watt is preferred for it's small size, but a 1/4 Watt is OK.

It's recommended that the circuit traces be followed to other components already attached to them and the standard resistor be soldered to them at those points for added strength.

Mounting a standard resistor to the pads meant for the SMD part means the resistor will have to be mounted vertically and the additional stress in mobile operation could and most likely would damage these circuit traces over time with the vibration of the moving vehicle.

After the resistor is added and before the power is applied to the radio, short out the two Reset Pads illustrated in the photo below.

The conversion is now complete.



I found this mod info at The CB World Informer, unfortunatly I have lost the URL of the site.

Magnum 357DX Adjustment Locations


"S" Meter RV-1
Power Meter RV-8
AM Power Maximum Adjust RV-16
FM Power Maximum Adjust RV-14
AMC - AM Modulation RV-4
FM Deviation RV-3
Driver Bias RV-13
Final Bias Adjustments RV-11 & RV-12
Carrier Balance RV-6 Unmarked Near Center Of PCB


If you have more precise information on any of these radio's Email Me !!!

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