" bravely wrote to "All" (25 Sep 05 15:11:35)
--- on the heady topic of "modding a pc power supply"

ke From:
ke Xref: core-easynews sci.electronics.repair:343101

ke I have a salvaged pc power supply I use as an adjustable bench supply.
ke But it won't go above about 14.9 volts. Apparently it has an
ke overvoltage protection circuit. The board has a TL494 (house-numbered
ke equivalent), and the only other chip on the board is a dual
ke comparator. The power supply is a Fortron/Source FS-250S40G.
ke I have another supply that also hits a ceiling when I adjust the
ke voltage, a Falcon Technology PE-250X with a 494 chip and a 14-pin chip
ke labeled DBL 339.

ke Is there some way I can disable the overvoltage protection on these
ke power supplies?


Sure look for a comparator IC something like a 339 or something and
ground the input from the resistors sensing each supply voltage.
Some better supplies have a crowbar detector sensing the 5 volt line
and are designed to self-destruct if there is an overvoltage.

Beware however NOT to exceed the voltage rating of the filter
capacitors as these will readily explode if used outside their specs.

Accordingly, the 12 volt supply might only be good for 16 volts tops
but remember corresponginly less current as well. If rated 12V @ 8
amps then it can only supply 6 amps at 16 volts. Otherwise fizzzzt!

A*s*i*m*o*v

.... The current limits placed are based on resistance