Mu multimeter measures 0 when I try to measure between L and N.
Unfourtunately I dont have a bench psu. Any other tips on how to proceed?
A much easier way to test is to simply desolder/disconnect the diode bridges. Then you should be able to measure some AC voltage (make sure you don't have your meter set to DC!) at each of the secondaries when the transformer is powered up. If you get the 27V you should be getting, then the trafo is likely OK and the problem is downstream - diode bridges, voltage regulators, capacitors on the power rails, etc. If you don't get any meaningful voltage there and the primary is powered (i.e. has those 240V on it - careful there!), then the trafo is likely shot and you will need to replace it. Sourcing a mains transformer with 2x24V or so output shouldn't be that difficult these days - the exact voltage likely isn't critical as the power supply produces +-15V out of it.
If the trafo is good then disconnect everything from the power supply module so if there is a fault you don't blow it (and also if the mixer circuitry is actually faulty it will allow you to fight only one battle at a time). Then start testing each of the power rails - is there an output voltage? If not, you need to track down why from the schematic. Try to divide the circuit in in parts and measure voltage - e.g. if you have DC voltage after the diode bridge and before the regulator but nothing at the output, then the problem is likely in the regulator. Etc.
Argh crap, while waiting for more help I actually desoldered all the diodes to check if they were working, they were, so I soldered them back in hehe...
In the meantime I got some very good help from a geerslutz member, I will quote him here for reference it sounds like the below information is enough to conclude that the transformer is indeed kaput? If not then I will continue with your very helpful suggestions!
This is my best guess for how this is wired. But without access to the unit and a meter, I can't guarantee its accuracy.
It wasn't clear whether the voltage selector can be removed (taken out of the circuit) or not?
I would remove the voltage selector (plug-in?) to avoid erroneous continuity readings.
With everything disconnected, I would expect to find a rather low resistance between (1) and (3) and infinite resistance (no connection, open-circuit) from (1) to any other pin on the transformer.
And I would expect the same resistance between (4) and (6), and no connection (infinite resistance) to anywhere else on the board.
With the voltage selector plugged back in and power applied to the board, I would expect to see 240V between (N) and (L)
And I would expect to see 120V between (1) and (3) and between (4) and (6)
I am assuming you have 240V power mains voltage.
Which resulted in:
Resistance measurements points:
1-2: 171 ohm
1-3: 195 ohm
1-0: open circuit, no-connection
1-4: open circuit, no-connection
1-5: open circuit, no-connection
1-6: open circuit, no-connection
1-0 (second 0 in photo): open circuit, no-connection
4-2: no-connection
4-3: open circuit, no-connection
4-0: open circuit, no-connection
4-5: open circuit, no-connection
4-6: open circuit, no-connection
4-7: open circuit, no-connection
4-0: open circuit, no-connection
Voltages:
N-L: 237 AC volt
1-3: 0 volt
4-6: 237 AC volt
So from above he concluded that the first winding 1-3 looks ok but that the second winding 4-6 is "open" so that the transformer is dead :deadbanana:
Apparently my measurements indicate that the first winding (1-3) looks OK.
But the second winding (4-6) is "open", so the transformer is dead.