Korg Triton SMPS fault

[Graham Tinkers]

Hi All,

I am trying to repair a SMPS out of a Korg Triton, I am not having much luck as I don't usually work on mains stuff so I thought I would turn to the forum for assistance. The outputs are +5, +15 and -15, all the voltages read correct but when under load the voltages drop sharply; the +5 rail drops after about 1 amp load is applied, the +-15 volt rails drop with only 10ma on them (with or without the +5 volt load). I have tested Q1, Q2, Q3, Q5, PC1, IC1, IC3, IC4 and they all seem fine, the electrolytic Caps look fine, no signs of leakage or bulging. Could IC2 the voltage reference be the issue or one of the man Triton PSU.pdf (71.59 kB - downloaded 77 times.)y Zenner or smd caps?

Kind regards,
Graham

[abdulbadii]

what max current rating stated?
try cross-check MM capable of reading within the rate range
slightly better is AMM (analog MM) than DMM if it has such capability

if reading is less 79-85% than current rating stated, some caps have aged and borne ESR

it demands quality ESR meter to read all on-PCB caps

[Graham Tinkers]

Hi abdulbadii,

Thanks for the reply; I have the the service manual but it does not mention the current rating of the PSU, putting and LED and a resistor across the +-15 volt rails causes them to drop by 1 volt, if I put a 50ma load the voltage drops to about 7.5 volts. I will try replacing all the electrolytic caps on the output side to see if it make a difference.