yx-305d bench power supply decreasing voltage problem

[ashan000]

This power supply is 30v 5amp. Problem is when turned on after about 3 minutes voltage starting to decrease slowly. (like - 5.8 > 5.7 > 5.6 > 5.5) can't see any damaged component or dry solder joints. Checked main 2 transistors with multimeter. Reading seems ok. Tried changing potentiometers(both coarse and fine) still the same situation. Can any one help me to troubleshoot? What voltages to check? Any ideas helps to fix this. thank you.!

[stj]

probably an op-amp drifting as it heats up - do you have freezer spray?

[ashan000]

No freeze spray. But I tried rosin smoke method to see if any component gets heats. only one resistor gets heats a bit. could it be the problem? i mark that resistor with white color in attachment.

[stj]

i'm not saying an opamp gets hot, i'm suggesting it's just drifting with temperature.

[CapLeaker]

No freeze spray. But I tried rosin smoke method to see if any component gets heats. only one resistor gets heats a bit. could it be the problem? i mark that resistor with white color in attachment.

Use a can of air (air duster) upside down. Instant freeze! You also could heat a component with an hair dryer or hot air station. This should accelerate your problem fast!

[Agent24]

I recall having a similar issue in the power supply of a device, turned out the pass transistor (TIP42 or such) was dying and eventually went open circuit