Marty:Replacing Capacitors and Clock Battery
Since Marty is a much older console it is not recommended for any learner to use a desoldering gun on the substrate. It is strongly recommended that you have adequate experience in desoldering (IE you didn't just purchase your desoldering equipment) that you need to use a hand pump and slightly lower temperature settings when removing capacitors from Marty motherboard.
RTC Battery
Some computers rely on RNG from a battery-powered IC. However, you're lucky as Marty and FM Towns computer doesn't use the battery for that. Marty only uses the battery to store time information which is generally only visible in TownsOS setting or when you write save game data to a floppy disk as it would have the set date. For most gaming purposes you really don't need or require to change the battery.
The battery is a CR2450 type. It can be removed and a socket for a CR2032 can be used.
Marty with socket and CR2032
Main Motherboard Revisions
Marty had two different revisions with one having the radical amount of bodge wires and the other not as much. Don't touch the bodge work at all. Just work around it.
Marty Revision with Bodge Work
Alternate Marty Revision with no bodges
Capacitor kits
Capacitor kits are available at Console5 and are compatible with both motherboard revisions.