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Replacing the Memory Backup Coin Cell in the Radio Shack™ HTX-202 and HTX-404
by Richard Luts KD4SEV
Instructional article by Craig LaBarge, WB3GCK
Edited and HTML'd by Mike Morris WA6ILQ
The article below and the PDF instruction file is oriented towards the HTX-202 and completely ignores the UHF HTX-404. Be assured the procedure is absolutely 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 an 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 socket and a new coin cell in hand, and after a short session on the workbench I was back in business.
Now to deal with the main battery issue:
After careful consideration I chose the IC-8 AA pack from Batteries America. This is a shell that holds eight AA batteries in any configuration, NiCad, Ni-MH, Alkaline, Lithium, and Carbon-Zinc. Additionally the IC-8 can recharge the rechargeable batteries via the standard BC-35 drop-in charger as well as a built in coaxial power (charge) jack.
I am back in business and with the addition of eight 2500 mAh AA
rechargrable 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. And
if I'm out in the boonies and run out of charge I can pop in 8 AA penlight
batteries and I'm back on the air.
Richard Luts KD4SEV
Click here for a step-by-step procedure by Craig LaBarge, WB3GCK 233 KB PDF file
A web page (with photos) on the same topic by the same author
A few relevant 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 has a distinct effect on the voltage produced. 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. Note the purchase date of the cells on the zip-lock bag with a Sharpie pen. You can refrigerate the batteries (do NOT freeze them) to extend the shelf life, just let them warm up overnight before use. 3) Ideally you would have two holders and two sets of cells. The middle of a disaster operation (even if it is just a weekly roll call net) is the time to swap packs, not to swap cells in a pack. 4) The current drain by the memory chip from the coin cell is measured in hundredths of a microamp - which is why the cell the size of a quarter can last ten to fifteen years. The resistance of a fingerprint - 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. One acquaintance had a piece of equipment with a soldered-in memory backup battery - he salvaged a coin cell holder from an old computer motherboard that he soldered to a piece of perf board and mounted to the inside of the equipment case (i.e. he used a cell holder and some twisted pair wire to relocate the call to a more convenient area to make future replacement easier).
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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.