Hi,

The GK60 trivolt PSU takes a DC input (20V to 70V) and has three outputs (all adjustable), rated 5V @ 6A, +12V @ 1A, -12V @ 1A, max total 60W.

Repaired two similar units, both with no lit LEDs.

First unit a check on the controller IC3 (UC 3843) showed 0V on pin 8 (Vin).. This was traced towards C16 47uF 63V which was shorted. Replaced and PSU worked fine.

Second had 7V on IC3 pin 7 (worker had 12V). Replaced C16 and V1 (+5V) and V2 (+12V) came up OK, but V3 (-12V) was only -6V. Tried adjusting output voltage but would only go up to -7V, and applying any load caused output to collapse.

I suspected the -12V regulator (LM337T), as this had a good -15V on its input. To remove this first had to remove main V3 smoothing capacitor (470uF 40V), this tested OK. Once regulator was removed found that 100uF 25V (across the V3 output) had ESR of about 3 ohm. Removed it and it was only 1uF. Replaced with 33uF 35V (as I had a Rubycon spare) and refitted main smoothing cap and new LM337T. V3 came up OK and could drive 12 ohm load (1A) fine at -12V.

nb There are several similar Vero PSUs, not sure if the replacement Verotec unit has the same circuit. C16 is near the front panel on the right and is easy to get to.

Regards,
John