Hi guys.
A friend of mine has a EM-U Proteus 2500 synthesizer, its internal power supply shuts off after a few minutes and then tries to turn on again. When turning back on immediately after the first shut-off, the few minutes become shorter each time. When checking the PSU output voltages after the first shut-off, they are lower than expected (+12v and -12v becomes +11.4 and -11.4v). On the pcb right next to the power input connector, it says +/-15V but the PSU only throws out +/-12V. The unit turns on just fine. I don't know if this means anything...
On the GearSpace forum, some user had a similar issue with this PSU, here is a quote from one particular thread:
Any ideas?
Thanks in advance.
A friend of mine has a EM-U Proteus 2500 synthesizer, its internal power supply shuts off after a few minutes and then tries to turn on again. When turning back on immediately after the first shut-off, the few minutes become shorter each time. When checking the PSU output voltages after the first shut-off, they are lower than expected (+12v and -12v becomes +11.4 and -11.4v). On the pcb right next to the power input connector, it says +/-15V but the PSU only throws out +/-12V. The unit turns on just fine. I don't know if this means anything...
On the GearSpace forum, some user had a similar issue with this PSU, here is a quote from one particular thread:
Well, I replaced 2 caps and about 4 resistors in the "Soft ON/OFF" path, and removed as much of the gump as possible and it didn't do the trick. I know that if it was a faulty cap in the output stage. it would not turn on at all."The power supply is easy to remove from the command station., is attached to the bottom with 3 bolts. I removed it and sent it to the technician. He has never seen a Command Station or similar, .....
After checking it, he asked me if the "device" had a soft or standby switch , apart from the ON/OFF at the back panel. He said a resistor or a capacitor in charge to receive or process the signal from the Soft ON/OFF button was faulty.
He replaced it, and the sudden shutdown problem was resolved. And also the loud white noise never came back...."
Any ideas?
Thanks in advance.
Attachments
High ESR capacitors will allow the power supply to switch on. As it warm the ESR increases to the point at which it no longer works as a capacitor.
Pay attention to the feedback and main tank capacitors.
Pay attention to the feedback and main tank capacitors.
This PSU supposedly provides +/- 12V DC but I only measure +11.45V and -11.40V. I still turns on for a few minutes when it has not warmed up, before it starts to fail. During the whole time, I can hear a slight clicking noise. Could there be any regulator in the circuit that might have become faulty?