Samsung SyncMaster 713N: General purpose capacitors in the power supply!

[lexwalker]

It was quite some time ago I've mentioned about seeing general purpose or standard capacitors being used in a switching power supply especially at the output filter section (right after the rectifiers). Well, here is one of them, a Samsung SyncMaster 713N LCD monitor with those type of capacitors at that critical section mentioned...

- Image #1: 2x 1000uF 10VDC 105C, CapXon KM series (for +5V rail, right after the rectifiers)
- Image #2: 1x 330uF 10VDC 105C, Samxon KM series (for +5V rail, right after the choke/inductor)

Furthermore there were no ceramic capacitors in parallel with them! Surprisingly they lasted this long (in a switching power supply environment).

Anyway, the problem with this monitor was 2 seconds to black. The faults found were badcaps and a blown MOSFET...

- Image #3: 2x 820uF 25VDC 105C, CapXon GL series (for inverter power rail)
- Image #4: 1x SP8M3 MOSFET (for inverter transformer)

Already fixed/repaired the fault by replacing them. That LCD monitor is now up and running...

[stj]

Re: Samsung SyncMaster 713N: General purpose capacitors in the power supply!

Furthermore there were no ceramic capacitors in parallel with them!

i'm surprised anybody even knows about that old design trick anymore!

[lexwalker]

Re: Samsung SyncMaster 713N: General purpose capacitors in the power supply!

i'm surprised anybody even knows about that old design trick anymore!

Seen plenty of this "trick" on ye' olde Creative GigaWorks speaker systems (using CapXon GS, Decon SAII and/or Su'scon SL series capacitors right after the rectifiers). Some SMPS type AC adapters also uses this "trick". All just for cost cutting...