Misc. Power Supplies

[channelmaniac]

Model: PRT PRO65-3
Symptom: Dead

This was a switching power supply in a piece of network gear that was basically an embedded PC system in a small 12 x 9 x 2.5" case. The power supply was too small to easily replace and the PC was to be used in as a MAME system.

Pulled the power supply out. There were no shorted diodes, bad capacitors, or other bad parts to be found in the supply. Everything checked out perfect until running continuity checks on the main transformer. The primary had 3 legs and only 2 had continuity. Pulled the transformer off the board to check it and the middle leg on the primary side had a wire that wasn't fully stripped of enamel insulation and wasn't properly soldered. Cleaned the enamel off the end of the wire, rewrapped it around the pin, and resoldered it. Reinstalled the transformer and hooked the power supply back up. Problem fixed!

[channelmaniac]

Model: Astron RS-7A
Symptom: Low output

Output was only 10.8 volts. Replaced 2 leaking capacitors and one shorted capacitor. Replaced bad 2N3771 transistor. The transistor did not fully short, but instead read 76 ohms from base to emitter.

[channelmaniac]

Model: Astron RS-7A
Symptom: Poor voltage regulation

The output voltage would fluctuate from 13.5 to 14.1 volts. Replaced bad 1000uf @ 35v filter capacitor and tested.

[channelmaniac]

Model: RS-10S
Symptom: Low output

Voltage output was around 1.2 volts. Replaced 2 leaking capacitors. Replaced the 2N3771 transistor to finish the repair. The transistor was open on one leg.