Hardware Hacking

There is a jumper inside the Alinco DX-77T to provide +8v bias on the
microphone audio + line. If you enable this Jumper you can use
Electret microphones with out having to build a separate voltage
insertion circuit.

JP1 is just to the rear of VR14 the Microphone Gain control on the PC
board. You can find JP1 on the schematic (which came with the radio)
Just above VR14, and just left of TP1. The bias circuit consists of
R338, R339 and C281 all of which are already present on the board.
Actual bias voltage will be less than 8v depending on the load
presented by your microphone.

I used a magnifying glass, and a sharp grounded soldering iron to
bridge the solder pads JP1. Be sure to open up the original hand MIC
and install a capacitor in the audio line to avoid having DC running
through the coil of the dynamic microphone.

Alinco DX70T Mod

This mod is a little tricky to perform, since it uses surface
mount devices, so I TAKE NO RESPONSIBILITY IF YOU BREAK YOUR RIG.
Alinco, further, in their mod sheet, warns that performing this mod
incorrectly will NOT BE COVERED via warranty. At first, I tried using a
Salami sized soldering iron— take my word, get a good, very fine point
iron of about 15 or 20 watts max! Make sure it is static guarded too.

Ok…Here we go.

1. disconnect power
2. disconnect antenna
3. remove control head, disconnect control cable
4. remove 4 screws on back of control head,
5 remove (unsnap is more like it) the control head back panel.
6. THE MOD:

Once you have the back panel removed, and using the big VFO knob as
your guide (circuit board facing you, LCD display not facing you). The
VFO knob should be on the left side. On the right side, in the lower
right hand corner, you should see 2 distinct columns of chip resistors.
On the board, they are NOT labeled, but I will draw the diagram below
to help you. You cant miss these because there are 5 chip resistors in
the left-hand row, and the right-hand row has 7 chip resistors. Above
both rows is a solder-pad.

a(::) h(::)
g-
i-
b - j-
c - k-
d - l-
e - m-
f - n-

Several chip resistors will be soldered in, depending on the model
of your rig, and a solder pad is jumpered. Here are the mods per
Alinco:

a. 45-60 Mhz TX/RX - solder a 0ohm or jumper across location i
b HF RX down to 30 Khz - remove the jumper m
c. beyond just Mars Mod - TX/RX everywhere remove both jumpers c and e
d. HF RX up to 35 MHZ - solder a bridge across pad a

After performing the above mods, reassemble the unit.

7. DONT FORGET to reset the microprocessor (with the radio off, hold
the F button and simultaneously turn the power on.
All memories are wiped out, but the new bands are opened.

I’ve tried all mods with my Alinco rig and can confirm they work. I am
able to pick up business band communication in the 46 Mhz range (FM), and
cordless phones in 46/49 range. It TX’s everywhere now too.

I do not take responsibility if you perform this mod incorrectly, and I
am not responsible for your operation practice if you choose to illegally
transmit out of band.

This mod gets rid of the “chuff” when tuning the radio that
becomes very annoying. This Mod also enables the speaker while you
are scanning. You will be surprised on how much you have missed.
I have done the mod and it is real easy. If you don’t like it
change it back. I got the mod from a unknown source, so it has not
yet been tested. I have heard of no complaint or problems.
The Mod is so easy all you need is a Phillips screwdriver and
5min’s. It’s that easy. Ok here it is:

1) Remove the batteries from the unit and turn it upside
down so the antenna is facing away from you.

2) Remove the six screws and remove the cover (be careful
that you don’t break the antenna wire)

3) Okay so far so good. Now locate the 8-pin cable.

4) Remove it carefully. Bend the second lead from the left
to a 90′.

5) Replace the cable and make sure the lead is not touching
anything.

6) Wa la [sic] it’s done. Not so bad now huh?

This mod will stop the annoying muting while tuning this Shortwave
radio

Remove the batteries and then remove the back cover by removing the 4
retaining screws. DO NOT remove the screw about an inch directly below
the whip antenna base! It holds the whip on. There will be a certain
amount of “fiddling” to get the back off due to the plastic section
that the volume control is inserted thru and other annoying “binding”
do-dads. Also, do not lose the tone switch plastic slide mechanism when
the back is removed. When the back is removed the rear of the main pc
board will be visible. Remove the 2 silver screws that secure this
board. Unclip the lower part of the board from the plastic clips. It is
not necessary to do this on the top side where the ferrite loopstick
is. Carefully lift the lower part of the board up until you can look
under it on the component side near the volume control. There are two
wire jumpers about a half-inch long with black sleeving on them that
are located on either side of a 9 pin SIP IC package (one of the audio
amps).! They are parallel to the SIP package and run along each side
of the IC. These are the mute lines to each SIP audio IC. Carefully cut
both of them and you’re done. Now put the thing back together and you
will find the tuning much faster and easier. Don’t forget to replace
the silver screws on the main PC board and the tone switch slide
mechanism.

1.) Remove control head from front of the rig.
2.) Disconnect the cable that connects to the back of the control head.
3.) Four screws hold on the back cover of the control head. Remove them
and the back cover.
4.) Clip the red and blue wires inside the control head. Then, put the rig
back together.
5.) Hold the Function key down on power-up to reset the rig.
6.) You will loose the contents of the rigs memories when you perform this
mod, so be prepared to reprogram them.