[SOLVED] Help needed for repairing the tracking in a bench dual power supply (0-30v, 0-3A)

Dear all,


I get hold on a 30 V 3A dual bench power supply Selectronic SL-1731SB, which seems to be the same
as the Velleman PS23023, and may some other ones.

Both canals are OK, but when I coupled them in series, the coupling is totally wrong

example
Tracking not activated : A : 5.4 V B: 10.3 V
Tracking activated : A :25 V B : 10.3 V

While one would expect to see both channels at 10.3V

I could find a schematic of the PS23023 on the web
https://www.velleman.eu/downloads/2/ps23023gbnlfresd.pdf

But I cannot locate the place I should look for some faulty component.
In the power supply, apart from the display section,
there are two same boards for each channel, an additional board for
the 5V channel, and a small board with lots of diodes that
I do not identify the role.

Can anybody help me, by telling me where to search for
the faulty tracking behavior ?

Thanks

Jacques

SOLVED !
https://www.eevblog.com/forum/repair/tracking-problem-in-a-dual-bench-power-supply/