Skytronic 650.682 dials not working

[tuffgong]

Hi there guys - Hoping someone can chip in on how I could repair a Skytronic 650.682 bench power supply. It powers on fine however none of the dials work (displays 0.00), I have tried putting a volt meter in the terminals to see if anything registers - nothing.  Opened it up and cannot really see anything obviously blown or burnt out, any ideas if its repairable or not?

Many thanks in advance
Cheers,
VJ

[Uunoctium]

maybe your model is the same as Vellemann
PS310/PS320 whose wiring diagrams you can find here
https://elektrotanya.com/velleman_ps3010_3020_power_supply_um.pdf/download.html#dl

What voltage can you measure across the fat electrolytics? Is at least one relay clicking at powerup?
Is the auxilary psu working? 7812, TL431 reference?

Voltage at base oft output transistors, than back at driver transistors, out at 741 voltage regulator. If psu out is inhibited by current limit amp, it seems that can isolated by desoldering on pin of diode V15

[tuffgong]

Hi there Uunoctium - I have not measured voltage across the Fat Electrodes.  When powering up, its almost silent apart form the fan that spins.  Not sure how to check the auxiliary PSU, there is 3 separate boards on the PSU.  Would it be the board that has all the Fat Electrodes on it?

Would the V15 diode be on the board where the Dials are on?

Many thanks in advance,
Cheers,
VJ

[Uunoctium]

The fat electrolytic capacitors are on the smaller rectifier board. Also voltage regulator 7812 and probably voltage reference TL431
I suggest doing this first to ensure, that the raw voltages plus auxiliary are present. That to exclude the worst case, an faulty transformer. All other defects are fixable.
The drawing is the closest to your model. Therefore components and their numbering are different, so you have to fiddel out their exact location on the boards.

(If realized the same manner in your device, the auxiliary voltages are measured against the (+) terminal.)

[tuffgong]

Hi there Uunoctium - that is fantastic, thank you so much for providing a test plan.  I shall try in the next week or so to test and report back.

Thank you again!
Cheers,
VJ