[SOLVED] - CEPEM IX3 induction hob power board schematic.

[shakalnokturn]

I have an induction cooker that fails to detect the pan.

The IX3 induction is a French/German design from the mid '90s that was used on many induction cookers until around 2005.
Sauter SED3N1 and Thermor 1448X1 are both based on this design.

To avoid the hassle of a little reverse engineering I'd need the component level schematics for the power board 7942-2391.
I know it must exist as there is one ancient post on this forum with a partial schematic of the housekeeping supply part of the board.

Thanks...

[shakalnokturn]

Aide toi, le ciel t'aidera...

The board i was trying to fix I had been given with unknown history.
One of the output switching relays was charred (a common problem) and there were many weak solders.
Before testing the PCB I set out to replace the relay and refresh the worst solder joints.

On first test when it failed to detect the pan I guessed that the output current measurement was the cause.
laying a spare inductor linked to an oscilloscope on the defective side of the hob revealed that there was no output to the inductor at all, so obviously if there is no output there is no current to be measured...

I checked all the housekeeping supply voltages to be OK. (-6V, +9V, +12V) Then spent a while drawing a partial schematic from a parts PCB I had hanging around.
Once my schematic was complete enough I started probing with my isolated scope, first on the working PCB to know what to expect.

On the defective PCB I was getting output from the UC3524 up to the collectors of Q3 and Q4 but nothing on the driving transformer primaries that are only separated by a 47ohm resistor.

A shorted transformer or shorted Q5/Q6 MOSFETS could have been the cause.
It wasn't, after scratching my head and probes at this for a few hours, I spotted it: A tiny solder link (that maybe I caused myself) between R11 and R12 on the transformer side shorting out the two opposite windings...

So this topic was an adventure and waste of time from and for me, myself and I but make the most of it now I've gone to the trouble...