Honeywell Digital "Round One" t-stat

Honeywell Digital "Round One" thermostat. I think it's a CT-2700 but I'll have to check. It's the one with simple two step programming.
The question is: Is there a battery in it? Something keeps the clock going when the furnace is off and there's no 24VAC, right? I don't think it could go too long on a capacitor alone. There's something on the PC board that could be a battery but I haven't probed it with a DMM yet.
It doesn't look replaceable--are you supposed to toss the stat when it goes bad? Ours is starting to have a flaky display where some segments of LCD numbers aren't working. Then again sometimes it's fine. I was thinking of taking a watch battery and (if I can solder to one without damage) stuffing that in there as a replacement. I can always hang a conventional cel outside temporarily as proof of concept. I mean the stat should normally be powered from the 24VAC so one would presume a bad battery would only cause loss of time when its off and not weird display artifacts at normal times but who knows.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
Add image file

Site Timeline is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.