Dell 65W- AC Adapter

[kacper69]

I have laptop Dell Latitude D620 with power supply model LA65NS0-00.
This power supply has a problem with capacitors ( I suppouse) , because when switch ON the laptop with connected power supply , the BIOS in laptop generate error sentence :~ power supply is not recognized , and battery is not charged.
But , when laptop is started from battery and after this power supply is connected , battery charging is OK.
I oppened power supply ( horror, because case is for "one use" designed ) , but i can't find any bad capacitors , any leak , any swollen caps.
Do you have some suggestions, whitch capacitors need to replace?

[hardwareguy]

Re: Dell 65W- AC Adapter

It may or may not be capacitors! The mains cap (the largest one, a 400-450V unit) is probably OK.

The unit is split by a transformer. If you flip the board over, the division between the high and low voltage sections can be clearly seen. There will be some circuitry linking the two for the regulation feedback loop. Usually caps fail in the low voltage section.

Be aware that some capacitors may fail without visual signs. To determine if this may be the case we need to know the brand and series. Both will be printed on the cap. Pictures are very helpful.

This is a Dell 3 wire PSU. Verify with a multimeter that all three leads inside the cable are intact. There is +, - and a signal lead.

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[kacper69]

Re: Dell 65W- AC Adapter

I checked cable before , all voltage are OK .
Problem is only in power supply , meybe in some capacitors whitch fail without visual signs.
When PS is "hot" , then laptop starts and recognize correct this PS !
I am looking for people ,whitch solved this problem before, in this PS is lots of capacitors...

[hardwareguy]

Re: Dell 65W- AC Adapter

You might not see voltage on the sensor wire...its data. The data pulses are likely too fast for a multimeter to read.

The ceramic chip type capacitors are likely good. It is the electrolytic caps that are the issue. I'd be surprised if there are more than 10 electrolytic caps in the unit. You need an ESR meter to check the caps if there are no visible signs.