ICOM IC735 lithium battery

[Derek Toeppen]

I have a 13 year old IC735. In the manual it says the
lithium battery is good for 5 years. After that it
should be monitored closely and replaced as needed.
The battery has not been changed in the 13 years.
So I am thinking its time to replace it.

The manual says it is used for the memory that
holds the frequencies and setup. And that it should
be replaced by Icom. At this time the radio remembers
all the setups and frequenies when powered down. So it
appears to still be functioning.

What happens if I remove the battery with the power
off? Do I loss just the setup? Or do I loss the operating
system for the radio?

Thanks in advance for any information.

Derek Toeppen, WA0ZTI

[Nitespark]

Post by Derek Toeppen
I have a 13 year old IC735. In the manual it says the
lithium battery is good for 5 years. After that it
should be monitored closely and replaced as needed.
The battery has not been changed in the 13 years.
So I am thinking its time to replace it.
The manual says it is used for the memory that
holds the frequencies and setup. And that it should
be replaced by Icom. At this time the radio remembers
all the setups and frequenies when powered down. So it
appears to still be functioning.
What happens if I remove the battery with the power
off? Do I loss just the setup? Or do I loss the operating
system for the radio?

I am going to make an assumption that this is the same or similar setup
that is used in the IC-745. I had one several years ago and changed the
battery and you really need to be careful. You should get a 3 volt
source and tack solder it across the points on the circuit board where
the existing lithium battery is connected. You may want to do the tack
soldering on the same circuit trace but away from where the lithium cell
is soldered in. Remove the lithium cell and replace it with the new
one. Then remove the tack solder leads and you should be set for
another 10 years or so. If you remove the lithium cell without the
backup, you will lose the radio programming and it must be sent back to
Icom for reprogramming. If you do blow the programming, you need not
send the entire radio (at least on the IC745). As I recall, the memory
board is socketed into the main board so all you need send back is the
memory board.

I went to Radio Shack and purchased a two AA cell battery back, soldered
the leads onto that with some fresh AA's and the battery replacement
went just fine. It is quite easy to lose the programming though. A
good friend of mine, who is a very meticulous technician, lost the
programming on his IC745. Perhaps his solder connection wasn't good or
he lost the memory voltage for a split second, but he had to send the
memory board back to Icom.

If your radio is 13 years old and the memory is on the same battery, I
would definitely make arrangements to replace that battery.

Andy
WD4KDN

[Bob Miller]

Post by Nitespark
If your radio is 13 years old and the memory is on the same battery, I
would definitely make arrangements to replace that battery.
Andy
WD4KDN

FWIW, I'm finally replacing the still-going-strong lithium battery in
my 20-year-old Icom 735, mainly because it is in the shop anyway, for
other work.

A few years back, an Icom technician told me the current drain is
15-20 nano-amps, and being a 180 mah battery, the estimated life works
out to 600 years or so!!

Bob
k5qwg

[Gary P. Fiber]

Post by Nitespark

Post by Derek Toeppen
I have a 13 year old IC735. In the manual it says the
lithium battery is good for 5 years. After that it
should be monitored closely and replaced as needed.
The battery has not been changed in the 13 years.
So I am thinking its time to replace it.
The manual says it is used for the memory that
holds the frequencies and setup. And that it should
be replaced by Icom. At this time the radio remembers
all the setups and frequenies when powered down. So it
appears to still be functioning.
What happens if I remove the battery with the power
off? Do I loss just the setup? Or do I loss the operating
system for the radio?

I am going to make an assumption that this is the same or similar setup
that is used in the IC-745. I had one several years ago and changed the
battery and you really need to be careful. You should get a 3 volt
source and tack solder it across the points on the circuit board where
the existing lithium battery is connected. You may want to do the tack
soldering on the same circuit trace but away from where the lithium cell
is soldered in. Remove the lithium cell and replace it with the new
one. Then remove the tack solder leads and you should be set for
another 10 years or so. If you remove the lithium cell without the
backup, you will lose the radio programming and it must be sent back to
Icom for reprogramming. If you do blow the programming, you need not
send the entire radio (at least on the IC745). As I recall, the memory
board is socketed into the main board so all you need send back is the
memory board.
I went to Radio Shack and purchased a two AA cell battery back, soldered
the leads onto that with some fresh AA's and the battery replacement
went just fine. It is quite easy to lose the programming though. A
good friend of mine, who is a very meticulous technician, lost the
programming on his IC745. Perhaps his solder connection wasn't good or
he lost the memory voltage for a split second, but he had to send the
memory board back to Icom.
If your radio is 13 years old and the memory is on the same battery, I
would definitely make arrangements to replace that battery.
Andy
WD4KDN

NO The 735 battery only retains the programmed memories the operator
programmed it is not like the IC-745, 751, 751A, 76,1 R71A, 271A / H,
471A / H, 1271A , M700, M700TY where if the battery expires the
frequency set up for those transceivers goes away.

If the IC-735 battery dies all your programmed memory channels with
revert back to 28 MHz frequencies.


Gary K8IZ
Washington State Resident
Registered Linux User # 312991

[Derek Toeppen]

Gary P. Fiber <***@verizon.net> wrote in message news:<***@4ax.com>...
Gary,

I am inclined to think you are correct. The battery only
supplies power to the CPU. Not an external memory. The CPU
has an EPROM window. So I think the radio programming is in
ROM. And the limited RAM inside the CPU only holds user
programmed frequenies.
But I could be wrong. It could hold calibration factors
or frequency range information for the PLL.

Have you tried this on an IC-735 yourself?

P.S. The current drain from the CPU must be very low. The
13 year old battery has a voltage of 2.946 volts under load.
Its still going strong.

Post by Gary P. Fiber

Post by Nitespark

Post by Derek Toeppen
I have a 13 year old IC735. In the manual it says the
lithium battery is good for 5 years. After that it
should be monitored closely and replaced as needed.
The battery has not been changed in the 13 years.
So I am thinking its time to replace it.
The manual says it is used for the memory that
holds the frequencies and setup. And that it should
be replaced by Icom. At this time the radio remembers
all the setups and frequenies when powered down. So it
appears to still be functioning.
What happens if I remove the battery with the power
off? Do I loss just the setup? Or do I loss the operating
system for the radio?

I am going to make an assumption that this is the same or similar setup
that is used in the IC-745. I had one several years ago and changed the
battery and you really need to be careful. You should get a 3 volt
source and tack solder it across the points on the circuit board where
the existing lithium battery is connected. You may want to do the tack
soldering on the same circuit trace but away from where the lithium cell
is soldered in. Remove the lithium cell and replace it with the new
one. Then remove the tack solder leads and you should be set for
another 10 years or so. If you remove the lithium cell without the
backup, you will lose the radio programming and it must be sent back to
Icom for reprogramming. If you do blow the programming, you need not
send the entire radio (at least on the IC745). As I recall, the memory
board is socketed into the main board so all you need send back is the
memory board.
I went to Radio Shack and purchased a two AA cell battery back, soldered
the leads onto that with some fresh AA's and the battery replacement
went just fine. It is quite easy to lose the programming though. A
good friend of mine, who is a very meticulous technician, lost the
programming on his IC745. Perhaps his solder connection wasn't good or
he lost the memory voltage for a split second, but he had to send the
memory board back to Icom.
If your radio is 13 years old and the memory is on the same battery, I
would definitely make arrangements to replace that battery.
Andy
WD4KDN

NO The 735 battery only retains the programmed memories the operator
programmed it is not like the IC-745, 751, 751A, 76,1 R71A, 271A / H,
471A / H, 1271A , M700, M700TY where if the battery expires the
frequency set up for those transceivers goes away.
If the IC-735 battery dies all your programmed memory channels with
revert back to 28 MHz frequencies.
Gary K8IZ
Washington State Resident
Registered Linux User # 312991

[Gary P. Fiber]

Post by Derek Toeppen
Gary,
I am inclined to think you are correct. The battery only
supplies power to the CPU. Not an external memory. The CPU
has an EPROM window. So I think the radio programming is in
ROM. And the limited RAM inside the CPU only holds user
programmed frequenies.
But I could be wrong. It could hold calibration factors
or frequency range information for the PLL.
Have you tried this on an IC-735 yourself?
P.S. The current drain from the CPU must be very low. The
13 year old battery has a voltage of 2.946 volts under load.
Its still going strong.

Post by Gary P. Fiber
NO The 735 battery only retains the programmed memories the operator
programmed it is not like the IC-745, 751, 751A, 76,1 R71A, 271A / H,
471A / H, 1271A , M700, M700TY where if the battery expires the
frequency set up for those transceivers goes away.
If the IC-735 battery dies all your programmed memory channels with
revert back to 28 MHz frequencies

Derek,

I worked for Icom America for 11 years until 2001 and yes I have
replaced the 735 lithium battery. As I said the only thing you will
loose is what you have programmed into the memory channels, so write
down what you have in those before proceeding. I would be inclined to
let it die and then replace it at that time.

I have never known an IC-735 that needed any sort of reprogramming
except for memory channels after you change the lithium battery.
there is not even a CPU reset that I remember on the IC-735. The other
transceivers I mentioned above are not the same and do use volatile
ram that is battery backed.


Gary K8IZ
Washington State Resident
Registered Linux User # 312991

[RDA]

I just bought a mint 735- thanks for clarifying this, Gary!

Dave

[Gary P. Fiber]

Post by RDA
I just bought a mint 735- thanks for clarifying this, Gary!
Dave

Your are welcome.. The 735 was probably in its day one of the best
little transceivers made, seems there are over 40,000 of them out
there. The receiver many time out preformed the larger transceivers
in some contest situations. I meet a couple of people who were at P40V
in the winning station sometime in the 1986 to 1989 era. They had 2
radios connected on each band with a switching arrangement that
allowed one to take over the antenna if he heard something. Many times
those ops said the 735 was doing better than transceivers like the
751A and 761.

I am sure the newer DPS based boxes will do more, but the 735 is no
slouch. Enjoy it.


Gary K8IZ
Washington State Resident
Registered Linux User # 312991

[Derek Toeppen]

Gary P. Fiber <***@verizon.net> wrote in message news:<***@4ax.com>...

Gary,

Thank you for clarifying this issue.

Based on this information, I think I will stop worrying
about the battery. When I loss the memories I will
know its time to replace it. Based on its current voltage,
that could be a number of years yet. Which means many
more trouble free years from the radio.

Derek Toeppen, WA0ZTI

Post by Gary P. Fiber

Post by Derek Toeppen
Gary,
I am inclined to think you are correct. The battery only
supplies power to the CPU. Not an external memory. The CPU
has an EPROM window. So I think the radio programming is in
ROM. And the limited RAM inside the CPU only holds user
programmed frequenies.
But I could be wrong. It could hold calibration factors
or frequency range information for the PLL.
Have you tried this on an IC-735 yourself?
P.S. The current drain from the CPU must be very low. The
13 year old battery has a voltage of 2.946 volts under load.
Its still going strong.

Post by Gary P. Fiber
NO The 735 battery only retains the programmed memories the operator
programmed it is not like the IC-745, 751, 751A, 76,1 R71A, 271A / H,
471A / H, 1271A , M700, M700TY where if the battery expires the
frequency set up for those transceivers goes away.
If the IC-735 battery dies all your programmed memory channels with
revert back to 28 MHz frequencies

Derek,
I worked for Icom America for 11 years until 2001 and yes I have
replaced the 735 lithium battery. As I said the only thing you will
loose is what you have programmed into the memory channels, so write
down what you have in those before proceeding. I would be inclined to
let it die and then replace it at that time.
I have never known an IC-735 that needed any sort of reprogramming
except for memory channels after you change the lithium battery.
there is not even a CPU reset that I remember on the IC-735. The other
transceivers I mentioned above are not the same and do use volatile
ram that is battery backed.
Gary K8IZ
Washington State Resident
Registered Linux User # 312991