rosaage
Newbie level 5
I have a Commodore 1084S-P VDE PSU (seperate board from the rest of the circuit) with some problems. If I connect it to 230V input it starts making a high pitched noise, measuring with a multimeter on the output pins gives me ~17V on pin 3 (C146) and 0V on the 25V and 125V rails. I have a spare working monitor with an Identical PSU, so I confirmed the monitor is working fine.
Since one psu was working I started moving over parts from the working psu to try and locate where the fault was as I was not able to meassure anything seemingly wrong. I have replaced:
Transformer T101, Input coil S102, All electrolytic caps except C146, C116 and C122. All transistors, Output diodes (D141,D142) isolator (IC101) and all red capacitors (Film?)
When I power it at lower voltages (<50V) all 3 outputs appear to charge up to the correct voltages, If I then increase the voltage it starts clicking slowly and the scope shows shorts on the output caps (C144). Increasing above ~200V it stays at 0V and the noise is high pitched.
One thing I find strange is that after letting it sit for some days and coming back to it when I power on the circuit it sounds completly normal untill my test leads touch the output caps, then it starts making the noise. Is the Multimeter load responsible for triggering something?
Since one psu was working I started moving over parts from the working psu to try and locate where the fault was as I was not able to meassure anything seemingly wrong. I have replaced:
Transformer T101, Input coil S102, All electrolytic caps except C146, C116 and C122. All transistors, Output diodes (D141,D142) isolator (IC101) and all red capacitors (Film?)
When I power it at lower voltages (<50V) all 3 outputs appear to charge up to the correct voltages, If I then increase the voltage it starts clicking slowly and the scope shows shorts on the output caps (C144). Increasing above ~200V it stays at 0V and the noise is high pitched.
One thing I find strange is that after letting it sit for some days and coming back to it when I power on the circuit it sounds completly normal untill my test leads touch the output caps, then it starts making the noise. Is the Multimeter load responsible for triggering something?