The notebook probably will not boot because the adapter output is oscilating approx +/-0.5v the output pi filter capacitors and inductor seem ok and there is same pulsing in front of it -any ideas what may be the cause?There are:nec2501 LK837-?,TL431c-regulator, fch200.. double diode,10n60 power mos thanks
Look at the feedback loop on the adapter.
If it pulses with no load on it, the problem is most likely an electrolytic cap in the primary circuit. If it only pulses with a load on it, there could be a short in the notebook. Chuck
Thank you both besides pulsing you can hear clicking in same rhytm,probably from transformer since lk837 seems to be optocoupler. With (non notebook) load output goes down to few volts!!There is also a controller chip but cannot see which is it How do you check that real big electolytic capacitor
The easiest way to check electrolytic capacitors is with an ESR meter. However, you could try replacing caps between 1 and 100 mfd in this supply. Chuck
Ok thanks however the pwm controller is ob2269
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