As much as I think I can add to provide some insight.
The system consists of two of the Induction PCBs - one each side each controlling two induction coils.
One one of the two boards, I went through and took out the bridge rectifier diodes and tested them with the diode test function on the DMM, they were all reading 0.450V in one direction only - good.
I checked the capacitors on the board (whilst they were still in circuit though) - they correlated to their values on the label correctly.
The same board I noticed there was obvious broken trace where an insect had shorted across the two traces (yay!)!
There's another board with some spring coils for the interface, this board has a BUS line, a 5V and ground terminal. It is this third board that I deduced a fault existed as the board had 240Vac on a terminal labelled 5V, the bus line doesn't have 240. I am aware the 5v line from the induction PCB is carrying 240vac and not 5Vdc.
I had a seperate power supply around and supplied it with 5vdc, and it still powers up, so the interface PCB is fine.
The two induction boards are linked together by 3 core cables, these contain 5v, ground, bus.
You can see in the left, below half way the two white connectors and two ICs these interfaced to.
The two ICs - look to be optoisolators - These are part number: CNY17-3.
My initial suspicion was that the two boards suffered from 240v on the 5v circuit (see insect joined two traces together), however! they both take 240v direct in and must rectify to produce 12v and 5v each side.
The optoisolators looks to be there for the bus comms only, as I continuity tested from the pins and found 0ohms to the 5v and gnd links on the PCB to the socket pins.
If there was 240V on one board on 5V, there would also be 240V on 5v on the other board....
In the top of the picture you can see on the left where active and neutral (in that order) are wired to that one board to terminals. There's a 30ohm resistor from the active. There's an inductor with a label CC05 on it, I thought that was one of the transformers initially, but it looks only to be an isolation transformer or similar? 240in, 0out?
All transformers on the board were tested to see if they were shorted across from primary to secondary.. not found.
Next to the yellow transformer at top right is a ST Viper17 IC.
Theres a plug nearby for a 12vdc fan as well. I deduce 12vdc must originate or be derived from that transformer. The 4 pin IC below the yellow right transformer is an opto- sfh617a-2
On the back of the board:
You can see around where the bridge rectifier diodes are the short the insect created, it goes from primary to secondary?? of the CC05 part / transformer near mains in.
That I suspect caused the alledged fault of 240v on the 5vdc and 12vdc (yes, it affects both 12vdc and 5vdc)..
Testing the transformers on the other board, I got the same for the "CC05" transformer - I got 240 on the primary side, and 0 on the secondary. The relay will be off as the control circuit is off.
But testing to where the 3 pin connectors are, there's now 19Vac there on all 3 terminals (from Earth, to each pin, 19Vac, 0Vdc). I expect to find, 5vdc, ground and bus..