I do not own a Kaboom, but from what I'm seeing, you are missing a spot in the battery compartment for a set of three batteires (AA's?) to provide backup power.
1. It's called a switch. There are
shunt springs involved, if you want to get detailed about it.
2. No.
3. No.
4. No.
Long story short:
The
operator's manual indicates that there are indeed backup batteries, so check the battery compartment again for a spot to add three AA or AAA batteries.
Long story not-so-short:
The
service manual seems to indicate a second Battery Source" BS2, consisting of three 1.5V batteries to make 4.5V. BS1 are the main batteries (10 cells) to make 15V:
It says that FW603 connects to CN193. CN refers to a connector jack mounted to the board, and FW refers to a cable, or "Flat Wire" cable that has a plug on the end of it that goes into the CN jacks. This image shows the battery board, with the source of the cable carrying power from both battery sources:
As you can see, FW603 only has 4 pins, but it has 5 pins on the schematic.
Or does it?
If you look above at the schematic image, pin 5 looks to be separated on the schematic, with those heavy dashed lines indicating that it's on a different PCB. My guess is that pin 5 is wired to a tiny PCB that touches the other (positive) end of the backup battery stack. It may be this little board to the right of the main battery board:
The service manual shows all of the unit's PCBs in the manner in which they are manufactured. That is, they are arranged in a single large PCB panel, with all of the individual PCBs for the Kaboom tied together with tabs that snap apart.
It looks like pin 1 on the battery board is the left-most pin, because that goes to BS2, just like FW603 pin 1 goes to the negative side of the 4.5V battery on the schematic. It would've been helpful if they had marked BS1 and BS2 on the schematic, but nobody's perfect, LOL.
You can also see that pin 3 does not connect to anything, just like the schematic. It's just a big pad.
Following FW603 "pin 5" we can see that it goes to pin 5 of CN193 on the battery board, which actually *is* 5 pins, marked as "BP" for backup power:
This routes over to CN191, which on the schematic accepts the cable FW601. Following this on the schematic, it goes over to pin 10 of a 13-pin connector on the amp board called CN602 and marked as "BUP" for backup power.
Looking at the amp board, there is only one place this can go, and it seems to have been mis-labeled as CN603:
This in turn connects directly to CN408 on the function amp board:
The main amp and function amp board seem to plug directly into each other without a cable. I see two other nearby connectors that also line up on both boards:
From here it seems to go to the microcontroller board by way of a hard-wired cable. It goes through a diode and into a circuit marked "Back Up" and a few other places.