Replacing the Memory Backup Coin Cell in the Radio Shack™ HTX-202 and HTX-404 Handheld Radios

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Back to Home Replacing the Memory Backup Coin Cell in the Radio Shack™ HTX-202 and HTX-404 Handheld Radios
by Richard Luts KD4SEV
Instructional article by Craig LaBarge, WB3GCK
Edited and HTML'd by Mike Morris WA6ILQ

The email below and the PDF instruction file is oriented towards the HTX-202 and completely ignores the UHF HTX-404. Rest assured the procedure is identical.

From an email received by Repeater-Builder from Richard Luts KD4SEV:
Recently my Yaesu VX-7 suffered battery failure, and I was loath to be without my HT on a daily basis and being of little cash, I looked to resurrect my HTX-202. The dreaded ERR-1 memory error had caused me to put it up on the back shelf of the shack many years ago, as well as the need for new batteries. After looking around on the internet, Google is our friend; I found great detailed instructions on replacing the 3-volt lithium cell by Craig LaBarge, WB3GCK. A short time later I had a coin cell and a socket in hand, and after a short session on the workbench I was in business.

Now to deal with the main battery issue.

After careful consideration I chose the IC-8 AA pack from Batteries America. This shell battery eight AA batteries in all configurations available NiCad, Ni-MH, Alkaline, Lithium, and Carbon, Additionally the IC-8 can recharge the rechargeable batteries via the BC-35 as well as a built in charge jack.

I am back in business and with the addition of eight 2500 mAh AA batteries, I have a great brick that runs for over three days between charging, puts out the full 5 Watts of VHF goodness and if a cell dies, it takes no time at all to replace them. For public service events or ARES, the longer run time, and heavier charge density makes this radio vastly superior to my newer FT-50-RD, and VX-7.
Great stuff

Richard Luts KD4SEV

Click here for a step-by-step procedure by Craig LaBarge, WB3GCK 233 KB PDF file

A few notes from Mike Morris WA6ILQ:

1) As mentioned above the Batteries America IC-8 pack holds eight AA cells. DO NOT mix alkaline, nicad or nimh types. The chemistry of a battery pack as a distinct effect on the voltage produced as it discharges. Nickel-Cadmium (NiCd) batteries deliver 1.2V per cell when fully charged, Nickel Metal Hydride (NiMH) deliver 1.25V per cell. Each 8 cell battery pack produces 9.6V from the NiCds and 10V from the NiMHs. The alkaline cells produce 1.5V each so 8 cells yield 12V.

2) If you are going to store the radio for a while (like in your "go-bag") remove the cells from the battery holder, and keep them in a zip-lock bag. If one or more cells leak the acid is not going to destroy your battery pack. Date the zip-lock bag with the purchase date of the cells.

3) Have two holders and two sets of cells. The middle of a disaster net is the time to swap packs, not not swapping cells in a holder.

4) The current drain by the memory chip from the coin cell is measured in hundredths of a microamp - which is why the cell can last ten to fifteen years. The resistance of a very thin film of skin oil is many times lower than the load resistance of the memory chip. If I have the physical clearance I always replace a soldered in cell with a socket.
A trick I learned while working at NASA-JPL is to handle the coil cell itself either wearing very clean rubber or latex gloves or to be VERY careful and not bridge the insulating ring between the positive and negative terminals with your finger or thumb, which leaves behind a leakage path for the cell. I used to have very bad luck replacing coin cells (the new ones would be dead in a month or two). My success rate has gone way up since I started being very careful to:
a) Clean the socket after installation (rubbing alcohol and let it dry for an hour)
b) Not accidentally leave a flux track on the board,
c) Not bridging the insulting ring as I grasped the cell as I soldered it into the board (in the case of soldered in cells) or
d) Not bridging the insulting ring as I slid the cell into the socket.

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This page initially created 01-Jun-2009.

Article text and photos are copyright © 2009 by Craig LaBarge, WB3GCK.
Radio Shack, Realistic, Archer and probably others are legal trademarks / service marks of Tandy Corp and no infringement is intended.

This web page, this web site, the information presented in and on its pages and in these modifications and conversions is © Copyrighted 1995 and (date of last update) by Kevin Custer W3KKC and multiple originating authors. All Rights Reserved, including that of paper and web publication elsewhere.