HP E3615A power supply slow ramp up

[gaminn]

One way to narrow-down the problem is to divide the path into two to determine which half has the issue.  For example, if you disconnect Q9's emitter (or remove Q9 entirely), and you still see a ramp up issue on the output posts, then you know the problem is downstream of Q9; if not, the problem is upstream.  Of course, since you've disconnected the voltage setting parts, you'd expect the output voltage to be close to the source voltage with the difference being does it still have the ramp up of few hundred mV over a minute.  Eg. use two multimeters with one red lead on drain (TP1), another red on source (right side of R1,R2), with blacks on -OUTPUT, to determine if there's narrowing voltage difference (TP1=23.0V and R1 right=22.2V increasing to 22.6V) or stable difference?

Thanks, I reall appreciate your help. I removed Q9 from the PCB. Now the voltmeter read approx 1.1V (no matter what the set voltage is), ampermeter reads 6.2A and there is smoke coming from R58 resistor. To me it seems that all the current goes via CR20 (overvoltage protection circuit). I removed also R101 to disable overvoltage protection and now the voltmeter reads 34.7V without any ramp up when turned on. I replaced Q9 by some random PNP transistor (BD244C), but that doesn't help at all, still long ramp up.

[pqass]

Ugh!  Sorry about that.   I forgot about the crowbar (CR20). 
I hope R58 (0.2R) didn't cook too badly. You should probably leave R101 disconnected for now.

However you did reveal some information... that the output remained at 34.7V and didn't ramp up from this value after power-up.  Also, since you replaced Q9 (and earlier U9), you've confirmed that the problem must be upstream of U9B inputs.

I don't recall if you measured U9C pin 1 (output) if that was experiencing a ramp-up after cold power-up. If you see it moving from 1.1V to 1.25V (WRT +OUTPUT/GND) then that would explain a movement from 4.3V to 5V on the output; with Vset knob set for 5V. 

[gaminn]

I don't recall if you measured U9C pin 1 (output) if that was experiencing a ramp-up after cold power-up. If you see it moving from 1.1V to 1.25V (WRT +OUTPUT/GND) then that would explain a movement from 4.3V to 5V on the output; with Vset knob set for 5V.

Yes, U9C.1 measured multiple times - e.g.  https://youtu.be/Vd9mJ_f1A_Q - stable. So the issue is between U9C.1 and Q9. U9 and Q9 already replaced. What else could it be?

I connected 5 ohm load to the power supply output, there is still the ramp up (5V voltage set).

I disconnected CR21 to disable constant voltage control circuit and connected back CR22 to enable constant current control circuit. Connected 5 ohm load, set voltage/current to 5V/1A. There is no ramp up with CC. Another confirmation that the constant voltage control circuit causes this issue. But how?