Modifications for the Kenwood TM-451


19-07-1998 Frequency expansion for the Kenwood TM 451 E

Demontage:

At first remove the upper case-cover, then the speaker can be removed and pull the connector of the speaker.

Then remove the lower part of the case. Then pull off the 3 knobs on the front side and remove the front side paneel. Bee carful, the front paneel is fixed through 4 straps which can break. Lift the straps carfully with a little screw driver or with Your fingers then pull the front paneel forward.

On the front side of the TRX loose 1 screw and the screws of the tuning knob. Loose the display with the transparent plastic frame carfully in forward. Remove the power button to side. A metall frame is fixed with 4 screws on side. Remove screws an pull the metall frame forward. The 2 screws of the processor platine front side can now be removed. Before taking out the processor platine, remove CTSS- or DFMF-units if they are there.

The processor platine is linked with 2 connectors with the F-platine. Pull these connectors softly! Take the platine with Your fingers near the connectors.

The processor is signed with "D 6433388F" and it is an 80-pin square SMD- ic. One edge is a little cut off, here begins the pin numbering counterclockwise. Between pin 64 and 65 that is right above the marked edge is a diode with a resistor in row connected. It is a smd-diode in a black pastic case. Remove it fully or solder it off only on 1 pin. Do not remove the diode in a field which is white framed.

Write down what You do when demounting the case and mount all together. At last make a reset (described in the manual).

What is new?

TM 451 E RX ranges:
136-173,995 MHz all rasters
300-469,995 MHz all rasters
800-999,9875 MHz only 12,5 and 25 kHz Raster
TX Range: 410-469,995 MHz all Rasters

To help with this mod. You want to be looking in the area were the lithium battery is. With the battery facing you, the IC is to your left. In my 451E the IC Chip D 6433388F is not visible because of a sticker on the chip.
Refer to the schemetic if in doughbt that's what I did! Still with the battery facing you, look left and at the top of the chip and from right to left count 5, this is pin 64 and 65. Now above you'll see a resistor with white edges, and directly above you'll see the black diode! that's horizontal, just unsolder one leg.
And don't for get to rerset the rig! But mine did it automaticly Hi.
I take no responsability if you damage your radio, proceed at your own risk, but it worked for me!



19-07-1998 TM-451E Low Power Mod

Open the upper panel, this one where you can put the ME-1
With the display front of you and the dissipator to the bottom, you will see at the upper right corner near the radiator some very small pot. VR The good one to turn for reducing power is VR102.
A screwdriver is all you need for this mod.