See the post just above this one, but to help you understand the predicament...
This is a multi pole switch. So there's a Common - to each pole - but not to ALL the poles - just unto itself. Each pole can be treated as it own "entity" - completely separate from the others "GANGED" together to work as one synced unit - providing output.
So look at the schematic at the link.
They "bridge" power from the 12V full power supply - to two terminals (the outer ones, USB and LSB).
The AM one to a specific terminal in the middle of both of them.
So when you rotate to either end of those 3 contacts
- the Common sees 12 Full Battery supply for SSB mode
(Remember the Switch is GANGED)
Also -
COMMON is the output of this portion of the switch (or specific pole) that goes to TP7 and TP8.
USB - AM - LSB are INPUTS to this switch
- they all rotate (together in sync)
- then there's AM MODE - which has the output of the AM Regulator, going to the MIDDLE Terminal as INPUT to the switch..
Remember this is a multi-pole switch
- also has a pole for MB3756 8V Regulator
- which has it's PIN output going to the INPUT of the Switch thru the COMMON terminal of that pole.
It FEEDS it's input as OUTPUT to the OTHER MODES via their terminal as output lines.
- - but uses the COMMON of the switch to engage the AM/USB/LSB modes as separate lines output and separately - from all the other poles.
- The MB3756 function is reversed, it's common - feeding power to other lines.
- The Difference is, the AM Regulator terminal is switched to to GIVE it's output to Common.
- - it's output is not wired as common
- - but connects to common when in that mode (AM).
- - it's Common then goes to TP7 and TP8.
- if the wire or that terminal got too much current - the COMMON can still connect to the other two - but the center one of the 3 might have blown open at the terminal to the COMMON when common rotates to that location (the foil/contact blown open like a fuse) and can't make the circuit complete - open line.
...runna pile-up on 6m SSB