|MAGNUM 257HP New Model Mods|
|SCHEMATIC and PCB DIAGRAMS|
MAGNUM 257HP New Model Mods
10 METER MOBILE AMATEUR TRANSCEIVER
FREQUENCY MODIFICATION / EXPANSION:
Step #1: Make sure Magnun 257HP is turned off and disconnected from power sourcel.
Step #2: Remove Speaker Side Cover & disconnect the Black & White Speaker Wire from the Rear of the Main PCB Board.
Step #3: Locate the small 1-1/2" x 3/4" CPU Reset Board located near the Front RIGHT panel of the radio located behind the Microphone Connector.
Step #4: Remove the single screw holding the small board to the radio franme.
Step #5: On the CPU Reset Board there are 4 jumper positions (CON-1 / CON-2 / CON-3 / CON-4).
Each jumper position will provide a different frequency range and configuration.
From the list below, select the desired frequency range and configuration, and move the jumper shunt to the corresponding CON #.
CON1: ~ 10 Meter Only (28.000 - 29.699 MHz)
- Default mode
- All functions operate normally
CON2: ~ 10 Meter & Expanded Mode
- At turn on, the radio defaults to 10 Meter mode.
- For Expanded mode, press FUNC and then press CALL for 3 seconds.
- To return to 10 Meter mode, repeat above steps.
for information on Expanded mode operation, see CON3
CON3: ~ Expanded Mode Only (25.165 - 29.699 MHz)
In the Expanded mode, the frequency range is divided into 10 Bands of 40 Channels each.
The Bands are shown on LCD display by letters (A through J) - Band E is regular 40 channel CB. To switch bands, press the CALL button (do not hold down for 3 seconds).
In the Expanded mode, either the frequency or channel can be displayed on the LCD. To switch between freqency display and channel display, press the FUNC button and then press the CALL button (do not hold down for 3 seconds).
On the channel display, the small number (0 - 9) to the right of the Band letter is the 1 kHz frequency display.
Example: If the frequency is 27.405, then the channel display will indicate 40 E5. (40) being the channel, (E) being the Band, and (5) being the 1 kHz position of 27.405.
Note! In the Expanded Mode, the RPT and SHIFT functions Will Not Operate.
CON4: ~ 40 Channel CB Only (26.965 - 27.405 MHz)
(Only operates on the regular 40 CB channels.)
Step #6 After selecting the desired frequency range and configuration, press the CPU Reset Switch (SW1) for 5 - 10 seconds.
Step #7 Reassemble the radio, turn on and test.
TUNE – UP / POWER TWEAKS
- 1 ~ Remove bottom cover
- 2 ~ Locate RV16. (AM Power)
- 3 ~ Adjust RV16 for a carrier of 10 watts on AM mode with the RF Power knob turned fully clockwise. With the RF Power knob turned fully counter-clockwise, the AM carrier should be 1 watt.
- 4 ~ Locate RV4. (Modulation)
- Adjust RV4 for maximum modulation.
- 5 ~ Locate RV9. (SSB Power) Adjust RV9 for maximum forward power in SSB mode.
- 6 ~ Locate RV8. (RF Meter) With RF Output power knob adjusted to show a 5 watt carrier, adjust RV8 just until the 3rd RF power bar lights up.