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That is exactly the one. But they are unobtainium (8moths is the shortest wait time I have seen) I will get a scope trace of the 15v line for you
smps fault finding
- Thread starter Stockleys
- Start date
So the click happens in 500mS interval. Voltage rises up till 15volts (yellow arrow) and then gradually lowers after the click (blue arrow) until the cycle starts again (green arrow). What strikes out is that the voltage remains stable for 1/4 of the cycle which indicates the regulation is active. Also that the "coold down" period is around 3/4 of the cycle.
How about start up, when the circuit is powered first time?
When the circuit has been off for long period of time, does it immediately start clicking or just after some time?
It is important to see the startup signal also.
How about start up, when the circuit is powered first time?
When the circuit has been off for long period of time, does it immediately start clicking or just after some time?
It is important to see the startup signal also.
Scope these points:
if VC pin exceeds OVP threshold or not.
MOSFET Gate tells us the switcher frequency.
Note: You should measure +15V and VC pin simultaneously by 2 scope channels to see the relation.
you may also scope:
FB pin the feedback voltage should be ok since the regulation kind of works.
CS pin tells us the current feedback level.
if VC pin exceeds OVP threshold or not.
MOSFET Gate tells us the switcher frequency.
Note: You should measure +15V and VC pin simultaneously by 2 scope channels to see the relation.
you may also scope:
FB pin the feedback voltage should be ok since the regulation kind of works.
CS pin tells us the current feedback level.
Will a laptop based scope be ok to use on these points? If the laptop is running on battery? I don’t have an isolation transformer and these points are no isolated from the mains. Scope says 35v max and probes are 10x, 500v max classII
I would measure the voltage with a multimeter first as these are at mains supply,.
Be extra careful when dealing with mains AC or high DC voltage. I don't see discharge resistors on 300VDC line so it could hold energy even when unplugged, check this voltage before touching the board !
Unplug mains AC input voltage, try to find the joints from the board (solder side preferably), solder a wire and connect scope probes, set your trigger levels and rest of the setups, power the board, operate your scope and take measurements, repeat if necessary.
Unplug the mains again, (check 300VDC), remove the probes and wires. If the space is difficult don't operate probes manually as you might touch something dangerous by accident.
Unplug mains AC input voltage, try to find the joints from the board (solder side preferably), solder a wire and connect scope probes, set your trigger levels and rest of the setups, power the board, operate your scope and take measurements, repeat if necessary.
Unplug the mains again, (check 300VDC), remove the probes and wires. If the space is difficult don't operate probes manually as you might touch something dangerous by accident.
its now working turns out D9 the 1418, although tested fine, was actually cracked. replaced it and it fired up perfectly.
next question thought, how much ripple is too much? not that my hantek scope is that acurate, but it looks like i am getting peaks of 1.2v above +15. and similar peaks on the 7v and 48v rails.
next question thought, how much ripple is too much? not that my hantek scope is that acurate, but it looks like i am getting peaks of 1.2v above +15. and similar peaks on the 7v and 48v rails.
