On Saturday, February 23, 2019 at 12:52:57 PM UTC-8, Jeff Liebermann wrote:
On Fri, 22 Feb 2019 11:08:32 -0500, wrote:

My Bearcat BC855XLT looses it's memory once in a great
while. Note: I am a service technician.

How long is a great while? There's a low leakage electrolytic
capacitor that will hold a charge to keep the memory alive for about 3
days maximum according to the user manual.

I did NOT find (Google search) a schematic for this scanner.

Same here. Some user manuals, but no service manuals.

This scanner has a "unique capacitor type memory back-up".

It's a low leakage type, probably one of these:
https://www.mouser.com/Passive-Components/Capacitors/Aluminum-Electrolytic-Capacitors/Aluminum-Electrolytic-Capacitors-Radial-Leaded/_/N-75hqw?P=1z0wrk5&Keyword=Nichicon+Low+Leakage+Alumi num+Electrolytic+Capacitors&FS=True

I would like to modify this scanner and use a battery back-up because
it is a HASSLE to reprogram the 50 channels.

You'll probably need to find the capacitor in question and measure the
operating voltage. Try turning OFF the scanner and measure the
voltage across all the likely culprits (large value electrolytics).
Anything with voltage when it's off is a possibility. You might also
check the minimum voltage needed to keep the memory alive. Then, add
a battery with a reverse protection diode to prevent the radio from
charging the battery.

Does anyone know where I can find (willing to buy it) schematic?
Or.....
Does anyone know where I can find the modification I want to make
to maintain memory?

Sorry, but it's the best I can do.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

To follow up on this problem, I sent John copies of the schematics from the BC855XLT service manual I have. Hopefully, he will be able to fix his problem with the channel memory. As a side note, my late mom had this same model scanner and it exhibited the same problems as John is having. So it would appear this problem was happening to other BC855XLT scanners too.