Scanning receiver (GRE/Realistic) corrupted O/S from a low memory battery - Page 1
Forum section: electronics / repair

author: videobruce
author_rank: Frequent Contributor
timestamp: July 21, 2025, 08:17:31 am
content: This VHF/UHF 'Scanner' is a GRE manufactured Scanner sold under the Radio Shack/ Realistic name, I've had ti for decades with no real issue other than changing out the backlight (a typical problem with this well known model).Out of nowhere when I went to use this (last time was around a month or two ago that I used it) the when I went to use this, the O/S apparently was corrupted showing a blank display (other than the backlight), no audio (other than the normal 'pop' when it was powered up), no squelch action (no inter-station noise), no response from any button and no response from the externial signal strength meter (Bill Cheek mod) which the needle will usually will bonce around as it is scanning.As in basically toast/fried as in dead other than a slight 'pop' in the audio when it was turned on and the backlight.The 1st thing I did was to check the memory battery which was low, but NOT dead. I replaced it, but little change. With nothing to loose, I did a reset and it came back to life, but I lost all the memory as expected.So my question, has anyone else had anything like this happen and why on earth would a 'low' memory battery cause this???BTW, I live in a city than never has lightning issues and my equipment is grounded,no static related discharges to the radio.

author: darkspr1te
author_rank: Frequent Contributor
timestamp: July 21, 2025, 08:44:13 am
content: What model is it? I have the Pro 2003 and that uses a battery for sram, remember from the manual that you need to change the battery when powered up to retain memory of it's gone too low you need to remove old battery and wait a short time for sram to reset then refit the battery. If this fails then try the internal MCU reset command, Hold 1+CLEAR and turn the device on the release the two keys.You may also want to check the caps in the psu side and on the MCU rail too, if original then are very old and could have failed the main power rail which in turn will drop the MCU rail.there are some diagrams online for the various stages as the were often used in different models (e.g my 2003 has same psu as 2004 but different rx layout)darkspr1te

author: darkspr1te
author_rank: Frequent Contributor
timestamp: July 21, 2025, 09:08:24 am
content: I did some digging around and found this pdf where bill talks about the 5v mcu control lines and how they are easily damaged and how they fail,https://archive.org/details/scanner-modification-handbook-v-2see page 19darkspr1te

author: videobruce
author_rank: Frequent Contributor
timestamp: July 21, 2025, 10:49:47 am
content: Pro 2004The problem was, I had no idea that the battery was low. The last time it was on, there was no indication of anything.I pulled the battery to test it which is when I discovered the charge state which the radio may not of considered it 'low'.I forgot about the battery change procedure, nor was I aware of this MCU reset procedure you pointed to.Thanks for the link, I scrolled down to the .pdf choice to download.

author: videobruce
author_rank: Frequent Contributor
timestamp: July 21, 2025, 11:34:27 am
content: Well, it's toast. I just re-programmed 2 banks, turned it off and back on with the same systems as originally reported. Nothing, no audio, no display, no receiver.Boat anchor.

author: darkspr1te
author_rank: Frequent Contributor
timestamp: July 21, 2025, 11:41:14 am
content: That to me sounds like the 5v has failed, if you read the "whole section" on the 5v rail you will come across the dry joints issue, a lot of early pro 2004 models had bad heat wave soldering and are known to just "stop"with no screen display and sound, both which rely on said 5v rail.it's worth checking for dry joints and dry caps , there are many videos on youtube for the 2004/5/6 range radios repairing everything from power to the audio amp.darkspr1te

author: videobruce
author_rank: Frequent Contributor
timestamp: July 21, 2025, 12:51:07 pm
content: Thanks anyway, it's really too old, it's hard to get at alot of those PS components and bottom line, all it's been doing was sitting since I have 2 other scanners far newer that are in use. It was nice in it's day, which isn't now anymore and with this unfortunate move to digital, it's mostly a boat anchor.