- Remove top and bottom covers.
- Remove the top screw from each side of the front
- Carefully rotate the front panel forward to gain
access to the control board(x53-3560-11 a/4). This board is mounted
vertically against the body of the transceiver. It is not the board
that is mounted in the front panel assembly.
- Locate and remove resistor R244 from the control
board. R244 is below IC12 ROM and above IC23. There are two chip
resistors, one on top of the other -carefully remove or break the
top one..it is easily fractured -that's R244.
- 5. Reassemble and then perform the cpu reset by
holding the A=B button depressed as power is turned on.
The TS-870 has a 3KC stock filter (YK-88S2)
located on the bottom side. By swapping out this filter for the
Inrad 4KC filter (#475), you'll be able to have better sensitivity
on receive with
less "hiss". On the transmit, you will gain better fidelity, the
lows will be slightly richer, the mids and highs will be a little
smoother and the separation between them are more noticeable.
Furthermore, if you are using rack gear, you can push your EQ's and
compressor harder without reaching the threshold of "tearings"
as quickly. You will NOT gain any more bandwidth by swapping out the
stock filter to this Inrad however. This is a fairly simple mod to
do. The most difficult part is the removal of the stock filter out
of the filter board.
A note on removing the filter board: You definitely want to make a
simple sketch as to which jumper goes to where or simply take a
digital picture of the thing before you start un-plugging.
For more information
Click on Here
Source courtesy of LA4WAA -
Original mod by W9AC
It has been documented by
several Kenwood TS-870 owners that feeding audio to the ACC2
rear input, instead of the front panel mic input, results in
lower distortion audio. This is because some of the speech
amplifier circuits are effectively bypassed that are the source
of the distortion, especially in the high frequency area above
However, because the ACC2 audio input of the Kenwood TS-870 was
designed for data audio (such as that from a TNC using the
digital modes), the audio characteristics of the ACC2 audio
input are attenuated below about 200Hz.
The following modification addresses this issue by changing the
value of the C131 capacitor that the ACC2 audio input travels
through, allowing low frequency audio to freely pass through the
C131 IN THE SCEMATICS:
Click to enlarge
C131 Modification Procedure:
- REMOVE METAL
SHIELD FROM PCB
Click to enlarge
- REMOVE ALL THE WIRES AND
RIBBON-CABLES AND SCREWS FROM PCB
Look for IC-23 - Capacitor C131 is under the PCB in that area.
- LOCATE THE CAPASITOR ON THE BACKSIDE
C131 is on the solder side of the PCB. With a beeping ohm-meter,
find the connection from pin 5 on IC-23 to the R137 (1K) witch
is under the PCB, to the left of C131 on the picture.
Click to enlarge
- SOLDER THE NEW CAPACITOR WITH
(DO NOT remove the original C131)
Use a mini 4.7uF/35V from ELFA (67-195-20). This fits nice under
the PCB. The positive lead to the direction of IC-23 and the
minus lead toward the front, like seen on the picture.
TS-870DRM TS-870 MOD
The modification described here has
been documented by others, and by all means, I am not the inventor.
However, this is the procedure I followed to modify my TS-870, and
also, provide an external connector that I can plug into for the
12KHz IF. As you will see, I integrated this into the ACC jack of
the radio, at the rear. Some mods on the Internet tell you to
desolder the IF cable, and place this in its place. This is NOT
needed! You can keep the IF cable, and do this mod easier.
The modification is very simple, does
not require ANY De-Soldering, and there are no holes you need to
drill in your radio!
The location of the 12KHz IF is
located on one leg on C144 Capacitor, which is located on the TX/RX
unit of the Radio (X57-4620-00 in your service manual). The Area of
Interest is as this:
You will need: a 1K Resistor, a 1mF Capacitor, a
Shielded Cable (RG-174 works great, and the Times Microwave LMR-100
- Connect one end of the resistor to the
capacitor, and leave the other end for connecting to C144 on the
radio. Connect the other end of the capacitor to the center
conductor of the coax. Shrink wrap around the area, so there are
no shorts, as the shield is not needed.
- Open the radio, and locate C144 as per the
diagram above. PAY ATTENTION to the side which the tap will be
connected! Is in on the c144 side which connects to the Q16 and
- Solder the free end of the resistor to this
- Run the cable around the radio, and then
solder the center conductor to the back of the ACC connector, on
PIN #1 (PIN#8 Can be used for your Ground to this). Just simply
tack the center conductor to the exposed pin (as seen in the
- You are done!
The reason for the 1mF capacitor, is that this
will provide proper coupling to the radio, and will PROTECT your
radio in case you short out the cable pins! PLEASE use it!
This is where the cable assembly is connected
This shows you where PIN#1 on the ACC connector is
located in reference to the chassis. Notice also how I routed the
LMR-100 cable in the chassis. This mod works AWESOME!
Remember it is Illegal to transmit out
of band. This Modification is for Informational purposes ONLY.
Doing such modifications on your radio may void any warranty and damage
All mods found on this database are offered to me by other amateur radio
hams or captured by Packet system.
KB2LJJ take no responsibility or liability for any damage done
resulting from any modification.
The KB2LJJ takes no responsibility for any damage during the modification or for
any wrong information made on this modification.