AKG N12 PSU calibration

I got a nice pair of vintage C12's with 4pcs of N12 PSU's, I would like to calibrate the PSU's for the new tubes, as I see the black "schrack" is a variable resistor for the anode voltage, the big wirewound resistors are for the heater, is there any documents available how to do that properly? (sorry I'm too young, or those parts are too old

another pic. - is this wirewound pair is for the heater adjustment?

Yes, I believe those two are the wirewound resistors that adjust the filament voltage. there's  clamp that can slide up and down the resistor thereby changing the value. To adjust, loosen the screw on the clamp and with a load on the supply gently and with small movements move the clamp to adjust for the right filament voltage. The filament voltage is present on the clamp so use something non-conductive to make the adjustments, or at least be careful not to short it. For a 6072 you want 6.3V. When you reach the right voltage tighten down the screw that holds the clamp. You might have to try this a couple times. The voltage can easily change as you are tightening the screw. Good luck!

Also if those are the original caps in there you will definitely want to recap it, otherwise I'd expect some pretty serious hum.

Hi,

Thanks, I found out that part already, as I see the anode voltage is fixed? I have 4 PSU's, I found 2 which is OK, the caps are also ok, no hum present.

I measured caps in N12 and all are in good condition, no hum, no problem.