Modding Cool Master RS-400-PSAR-13

[flyboy_ont]

Hi All

I would like to modify a Cool Master RS-400-PSR-13 400W PSU for 13.5v to 13.8v.

The PWM chip is a 2012. I've read that this can be done by changing resistors in the feedback circuit to the 2012. I have no idea how the 2012 works so no idea what resistors to change.

Any help would be greatly appreciated.

[CapLeaker]

Re: Modding Cool Master RS-400-PSAR-13

If you don't mind... why would you want to change it? To run ham gear? Most power supplies have a variable resistors near the PWM. One should change the output voltage on the 12V rail. Be careful and watch that the output voltage is not exceeding the voltage rating on the caps.

[flyboy_ont]

Re: Modding Cool Master RS-400-PSAR-13

Yes I would like to change it for ham gear. There is no variable resistor on the board to adjust.

I've been trying to trace back the 12V and 5V circuitry to see if I can figure a way to raise the voltage.

I already have 35v caps to replace the existing ones.

[CapLeaker]

Re: Modding Cool Master RS-400-PSAR-13

I just hope you aren't using it for your HF, as these power supplies aren't filtered that great. I have modded some ATX power supplies before, but I used those that had a trimmer in the circuit. Once you find the right resistors, you can take them out, wire an external trimmer on it and adjust the voltage also for bench use. There should be 2 resistors close to the PWM chip. Whats the part number of the PWM? Maybe you can get the pin out off it and figure out the resistors they use that controls the PW on the chip.

[flyboy_ont]

Re: Modding Cool Master RS-400-PSAR-13

Yes I want to use it for HF. Can I add filtering?

The PWM chip is 2012 and I have the pinout for the chip.

I have two other PSU's but they use an ICE chip (dont know the exact number off hand). Neither of them have a var. resisitor.

[flyboy_ont]

Re: Modding Cool Master RS-400-PSAR-13

https://www.badcaps.net/forum/showth...light=2005+pwm

This is the thread for the 2012 pinout.

[CapLeaker]

Re: Modding Cool Master RS-400-PSAR-13

Pin 13 COMP is the duty cycle control.

[flyboy_ont]

Re: Modding Cool Master RS-400-PSAR-13

Is this the pin I look at for changing the reisitors for a var. one?

[stj]

Re: Modding Cool Master RS-400-PSAR-13

does it have any opto-isolators?

[flyboy_ont]

Re: Modding Cool Master RS-400-PSAR-13

No opto-couplers.

[CapLeaker]

Re: Modding Cool Master RS-400-PSAR-13

Can we see some good pictures?

[flyboy_ont]

Re: Modding Cool Master RS-400-PSAR-13

I will have to take some.

In trying to figure if there was a feedback trace back to the 2012 chip, I started to disassemble the 12v and 5v section. On both the 12v and 5v section I pulled a cap, choke and another cap. After that it went directly to the secondary toroid windings.

Capleaker and stj thanks for helping so far.

[flyboy_ont]

Re: Modding Cool Master RS-400-PSAR-13

At the junction of the 5V winding and filter cap, a trace goes back to pin 4 on the 2012 chip, which is the 5V monitor line (I assume).

Could I put a voltage divider of resistors here to fool the chip it was getting less than 5V?