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Author Topic: TM-742A Back Up Battery Replacement  (Read 11865 times)
WD9X
Member

Posts: 3




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« on: November 30, 2009, 02:27:16 PM »

Can anyone give me tips on replacing the back up battery?  Also, is the W09-0573-05 the only battery needed.

tnx de Jay WD9X
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KA5IPF
Member

Posts: 1406


WWW

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« Reply #1 on: November 30, 2009, 03:10:28 PM »

That's the only one. Be careful removing the old one. They used plated thru-holes and if you pull them out it causes problems.
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KE4DRN
Member

Posts: 3746




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« Reply #2 on: November 30, 2009, 09:18:42 PM »

hi Jay,

don't forget to copy all your memory info
before you do the replacement.
some of us have placed a battery holder
on the pc board for the next battery change.

info on this group

http://groups.yahoo.com/group/tm742/

http://groups.yahoo.com/group/tm742/files/Battery%20Replacement/

please join other tm-742 fans

if you like I can email it direct to you,
I'm at     callsign@arrl.net

73 james
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N0UDM
Member

Posts: 1




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« Reply #3 on: September 06, 2014, 08:00:07 PM »

The backup battery is a 3 volt battery, so I found info from some otherowners who have successfully removed the internal battery and added a small battery holder externally so the battery can be changed easily. I modified my radio the same way, running the wires in the channel the same way as the fan wires above the top band unit and it has done just fine. As mentioned, be careful unsoldering the old battery. I used 24AWG strended wire to the external battery holder and it seems to be OK. Of course, the battery holder has to be somewhere external to the unit, so I notched the grate on the fan enclosure and put the wires through there and just attached the holder on top with double stick tape.
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KA5IPF
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Posts: 1406


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« Reply #4 on: September 06, 2014, 08:29:18 PM »

The backup battery is a 3 volt battery, so I found info from some otherowners who have successfully removed the internal battery and added a small battery holder externally so the battery can be changed easily. I modified my radio the same way, running the wires in the channel the same way as the fan wires above the top band unit and it has done just fine. As mentioned, be careful unsoldering the old battery. I used 24AWG strended wire to the external battery holder and it seems to be OK. Of course, the battery holder has to be somewhere external to the unit, so I notched the grate on the fan enclosure and put the wires through there and just attached the holder on top with double stick tape.

I question the logic of that for a battery that needs to be replaced every 20 years?Huh?? Maybe, some last a lot longer.
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K9YLI
Member

Posts: 1191




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« Reply #5 on: September 07, 2014, 07:17:48 AM »

also  that battery pn  looks like one thats  expensive..   a  2032 with tabs is  about  3 bucks  at  battery  locations.
also  it wil last  about 10 years so the   battery  holder is  just   nonsense to me.

removed the note about  power on. I think  when i replaced  kenwood batteries  you have to  pull the face off the  radio.

then again  you can  put  2  AA in a holder and  clip around the  memory  battery  while you replace it,  I think the memory is on the same  PC board,, as I have dis-assembled  kenwoods and not lost the  memory.
« Last Edit: September 07, 2014, 07:22:22 AM by K9YLI » Logged
KO6KL
Member

Posts: 5




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« Reply #6 on: September 17, 2017, 01:03:21 PM »

i have spent hours programming in all the repeaters on 3 band units... id rather sell it then do that again...
can you use a pc somehow to program the 742 ? perhaps with dtmf ?
ko6kL

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W9GB
Member

Posts: 3148




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« Reply #7 on: September 17, 2017, 03:15:09 PM »

Lithium Coin Cell Diameters of 20mm and 23mm are most popular.

Kenwood part number F20-0521-04 is a battery insulator
that is sometimes used with solder tab lithium coin cells in Kenwood radios.

In the Kenwood TS-440S transceiver,
this insulator is placed on the positive (+) side of the lithium battery (CR-2032/F2N).
https://www.digikey.com/product-detail/en/panasonic-bsg/CR-2032-F2N/P657-ND/2404062
====
Mouser has a catalog page of the more popular lithium coin cell solder-tab configurations.
Toll Road transponders use these solder tab cells (same reason Japanese mobile radio mfg. have since 1980) -- so they are READILY AVAILABLE and CHEAP.
http://www.mouser.com/catalog/645/usd/2235.pdf

Digi-Key has the full catalog of Panasonic lithium coin cells with solder tabs.
Majority are under $2 USD, BUT shipping can be an issue.
Lithium batteries can not be shipped via domestic passenger air carriers (no USPS Priority Mail)

https://www.digikey.com/products/en/battery-products/batteries-non-rechargeable-primary/
« Last Edit: September 17, 2017, 03:38:10 PM by W9GB » Logged
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