PC CPU voltage for power supply- Help?

[beaverfeaver]

I have followed the threads to convert my pc pwr supply to run a astro 109 charger. It works but I am getting 15.3 volts at my power tap. I used three yellow (12v) wires to it and 3 grd to the neg tap. I have used 2 10 amp 10 ohm resistors in parallel on a red and black supply. Is this too much? How can I change it? ps: its a 300 watt 6 amp supply..
Thanks for any help...Dave

[william541]

Raise the load resistance on the +5 output (ie remove one of the 10 ohm load resistors). This should lower the 12V output if you are concerned about it.

-Bill-

[beaverfeaver]

Thanks for your reply.. will it hurt the charger if I leave it alone? Thanks again...

[Comatose]

No. The charger is designed to run off a "12v" battery, which has a maximum charged voltage of 15v. 15.3 won't hurt a thing.

[beaverfeaver]

I have finished it and checked the posts with it running..I am getting 15.3 then it climbs to over 16... any suggestions...?
The astro flight 109 says up to 15v input...Thank you for your assistance...BeaverFeaver

[beaverfeaver]

I converted my power supply and in checking with a voltage meter, the voltage starts close to 15 and continues to climb... I have had it to 16.4 and shut if off. What is causing this and how can I control it??? any help appreciated. Thank you

[Andrew0820]

... I have had it to 16.4 and shut if off. What is causing this and how can I control it???

Most design guide complient power supplies have both low voltage and overvoltage sense circuitry built in. By standard, your PS should latch into the shutdown state around 15.6 volts max. Nominal latch values are 15.0 volts with a continuous steady state max of 12.6v under normal load and temperature. Given that you have readings over 16v, it appears that your overvoltage circuitry is not functioning. If you converted a newer PS, there may have been sense wires tied to the +3.3v, ground and possibly +12v. Generally, the remote sensing wire is there to compensate for voltage drops over long cable runs, but you may want to reattach them if they were cut away. Sense wires usually are the same color as the voltage rails, but are a smaller gauge and will be attached to the circuit board at a location different from the voltage supply wires.

I would also recommend that you try WILLIAM541's suggestion. By attaching two 10 ohm resistors in parallel, you dropped the resistance to 5 ohms. Most PS will increase output voltage to compensate for the higher load. If your voltage continues to remain high, try two 10 ohm resistors in series - this will lower the effective load even more -- if your PS will stay latched on, and the 12v rail is acceptable, leave them. The power consumed will be less and the resistors will run cooler.