YES, IT CAN BE DONE !
TH F6 and TH F7 is, actually, the same transceiver.
Well, there is a difference: one diode.
This modification will reset your radio and therefore
clear all pre-programmed memories, etc. Please write
safely police, aviation and cordless phone frequencies
saved in your memory;-)
difference between TH F6 and TH F7 is one diode. If you
want to transform your TH F6 into TH F7 or your TH F6
into TH F7, then you may fallow these steps:
First open your radio as described in the “MARS/CAP”
After that, locate those three diodes and one resistor
located close to the “Power” button.
I will call these diodes D1, D2 and D3, starting from
“Power” button, followed by the “R” (zero ohm) resistor.
Warning: these are NOT notations from Kenwood
On the original Kenwood TH F6 A you will find D1,D2,D3
and R all mounted. To convert your USA F6 model into F7
European model, you must remove the D3 (the one close to
the resistor) diode.
After modification you will get European ARS on 2m band,
no TX on 216Mhz band and all European options (Repeater
options, bands, etc.).
On the original Kenwood TH F7 E you will find only D1,
D2 and R fitted in. To convert your F7 European model
into USA F6 model, you must fit in one diode in the “D3”
After modification you will get TX on 144-148Mhz, TX on
216Mhz, USA ARS on 2m and so on.
Warning: transmitting on the 216Mhz band may be illegal
in your country. Also your antenna is only dual band, so
think twice before pressing that PTT button ;-)
All “MARS/CAP” modifications are still available for
you’re your new F6/F7 transceiver ;-)
will publish a few D1 D2 D3 R configurations I have
Kenwood TH F6A (TH-F6A THF6A) service menu switch
On TH-F6 transceiver, the “Service Menu” is
accessible only by opening the transceiver. The “Service
Menu” contacts are shown in the following picture, close
to the “1” and “4” keys.
It is obviously that this design is not very flexible
for “daily” use. Maybe this is why people are not (yet)
playing too much with “Service Menu” on this
This is why I decided to build an external switch for
“Service Menu”. My best idea was a Reed switch. I bought
the smallest one (thanks Good I got two of them ;-) and
I started “the best place for Mr. Reed chase”. In the
process, one Reed switch died ;-)
The best place I have found is shown in the next
All you need is two pieces of thin wire and one small
Reed switch. After the case is closed, entering the
”Service Menu” is done using a small magnet (from about
half inch distance).
Using this solution I was able to play with “Service
Menu” and find the
“low modulation problem”
I also think the power level on battery will be
interesting to “recalibrate”. I’ll be back in a few days
Kenwood TH F6A (TH-F6A THF6A) extended
images in this page are from TH F7E, so please do not be
fooled by those small differences in diodes
modification will reset your radio and therefore clear
all pre-programmed memories etc. Please write safely
police, aviation and cordless phone frequencies saved in
have never removed surface mount devices before, then
experiment on some old PCB's first, or even better, on
your friend’s TH F6 handheld, before destroying or
making a mess of your new radio. If your radios is not
new, go ahead, mess it up ;-).
sure you use a low wattage soldering iron and tweezers
to lift the components from the PCB. Or maybe you can
use those $2000 SMD soldering devices…
decide to do this modification, you do entirely at your
own risk. However, make sure first you have someone to
blame. Have you called your girlfriend today? ;-)
Remove the battery from the radio.
Remove the grey rubber protective cover from the
right hand side of the radio.You DON’T have to
remove as in this picture, just free up the SP, MIC
and DC IN. If fully removed, will be a little bit
hard to fix it back.
Remove the black plastic volume and frequency change
knobs by gently pulling them vertically.
Remove the locking nut from the SMA aerial
Remove the locking nut from the frequency change
encoder / volume control shaft.
With the battery removed, look at the rear of the
radio and remove the two screws at the bottom.
Now, Doc, let’s open your next victim. It's best to
gently open the radio from the bottom until you have
a gap of about 10mm. (Nurse, retractor please ;-)
Then hold the front panel in the palm of your left
hand and gently slide the main body of the radio
downwards with your right hand, until the aerial and
frequency change encoder shaft are clear of the
holes in the top panel of the radio. Take care not
to open the radio to fast, because the internal
speaker wires are very short.
With the radio opened up like a book, look at the
left hand side of the PCB just to the left of the
PCB mounted microphone. You should see three diodes
(if your transceiver is TH F6).In the next picture
you will see only two diodes and an open pad, since
the picture is from an TH F7E.
These photo's shows radio before modification(with
the third missing diode, as described above...)
Remove only the top diode. There still should be two
diodes in the middle and the bottom position.
Finally look just below the third diode and find a
resistor (zero ohm) to the left of the keypad number
"1". This also must be removed to complete the
This photo shows radio after modification.
Reassemble the radio taking care not to trap the
speaker wires and also check that the small joystick
and keypad membrane seats correctly.
will now Transmit and Receive in this intervals:
Kenwood TH F6A (TH-F6A THF6A) "defective
charging jack syndrome"
There are many reports
about the "defective charging jack syndrome". The charging jack (of
early models?) apparently is defective, causing the radio "not to turn
on" when the charger is disconnected. Looks like the switch inside the
charging jack is broken and not allowing the batteries to re-connect to
the radio when you remove the plug.
Another theory is that the "F1" battery fuse will open for some reason.
1) Send the transceiver back to Kenwood service, especially if it is
2) Try to remove the battery from radio and reinstall it back.
3) You may try (AT YOUR OWN RISK!) to touch a little bit the switch
inside the jack using an small screwdriver or a piece of wire.
Kenwood TH F6A (TH-F6A THF6A) "external
power source/charging syndrome
There are a few reports
about the Kenwood TH F6A transceiver that stopped working off an
external power source and also stopped charging the battery. The
transceiver is working ok on the battery.
In my opinion, this is a consequence of an "bad design" made by Kenwood
Please read the following scenario:
You are using an external antenna and an external power supply on TH F6.
Your antenna ground is common with the ground (minus) from your power
supply. This may be done from your grounding system or from an second
transceiver using the same power supply, or jus by an accidental touch
between the antenna’s shield and the case of your secondary transceiver.
Now, the best part: when you are using the external power supply jack on
your TH F6 A, the transceiver’s connector internal switch will
disconnect the battery’s minus from the transceiver’s ground. This way,
the battery will remain in the charging circuit and the transceiver will
be powered by the external charger/power supply.
Having the ground ALREADY connected to the transceiver (from the
antenna’s shield), your toy will be powered from the external power
supply BEFORE the battery is disconnected.
This way, momentary, the battery will be DIRECTLY connected on 12.0-16V,
depending on the external voltage ;-) . It will eat A LOT more current
from your power supply and the F2 Fuse will open.
Hopefully the battery is internal protected ;-).
Recomandation: When charging/using an external power supply,
FIRST connect the jack to the transceiver, THEN plug the charger/power
supply into the wall (this sequence is also described in the user
manual, without telling WHY ;-) . When charged, first unplug the
charger/power supply from the wall then unplug the power jack from your
1) Send the transceiver to your local Kenwood service.
2) Send the transceiver to your local Kenwood service.
3) DO IT AT YOUR VERY OWN RISK !
Well, if you live in Guyana (like me) and don’t have a local Kenwood
service, then you may fix the toy for your self ;-). You will need some
$2000 soldering devices ;-). If you don’t, you may use your old
soldering gun. I’ll not tell you how, you must have the proper skills.
If not, find someone with. If can’t find, go to step 1).
Now get the schematics. Locate the F1 and F2 fuses in the C2 area. I do
not have the PCB schematics, so you must find the fuses: The F1 fuse is
located on the same face with the power jack, close to the plus (+)
battery contact. Is having “F” on it (at least mine). On the other side
of the PCB you will find the F2 fuse, close to the power jack
connections. F2 is having the same dimensions like F1, but is having an
“S” on it. This fuse must be open. If it is, replace it. I was unable to
find one, so I just used a piece of 1.5cm of thin wire, which will do
the job. I also used a soft pack from an CPU computer cooler, just to
prevent the heated cupper to spread all over the transceiver in case of
“huh, id did it again” :-( .
Good luck! Waiting for “I did the job” reports
Kenwood TH F6A (TH-F6A THF6A) low modulation
the biggest TH F6A problems is the modulation level.
Compared with other transceivers, mine is 1/2 in 2m and
1/3 in 70cm, in terms of modulation.
One of the low modulation reasons is the microphone
design: there is no case opening for mic. Instead, the
sound must “travel” from the speaker’s holes, through a
little channel, finally finding the mic. Sometimes,
during assembly, the channel can be filled with speaker
Another reason is the “Service Menu” setting.
That it, do
not forget to close the transceiver ;-)
Open the transceiver (as described in the MARS/CAP
mod page) and check out if the mic channel is clear
(using a small piece of wire). If this is not the
case or the improvement is not enough (in most cases
it will be not! ) go to step 2).
Open the transceiver (as described in the MARS/CAP
mod page), power on and close the “Service Menu”
contacts instantly. The “Service Menu” contacts are
located close to the 1 and 4 keys, as described in
the following picture.
Warning! On the first service menu option, DO NOT
press “OK”! You have been warned!
Once in the Service menu, press “Right” on the
“Multi-scroll key” until you see a line like this:
“MAX:?? f1:??”. The “??” will be a hex value
between 00 and FE. Now press “BAND” to the desired
adjusting band. Turn the “Tuning Control” for a
bigger value. Press “OK” on the “Multi scroll key”
to set the new value. Check out with your friends,
not to get overmodulation. It will be better to make
this test with the case closed.
Repeat the adjustment for all bands.
On my transceiver, the best values are “FE” for 2m
band and “51” for 70cm band.
Enjoy your new toy
The KB2LJJ takes no responsibility for any damage during the modification or for
any wrong information made on this modification.