laptop charger repair??

red sean

Hi guys, just wondering is it possible to repair a laptop charger?
No output voltage. I opened it and the caps. look ok.
Is there anything obvious or commonplace I could look for?

Sorry for such an apparently stupid post. but just wondrin'!
I'm an electrician but electronics is not my field.

Thanks

ZENER

Is the output cable ok ? They usually break where they exit the case or at the connector end. It's very possible that the + & - have been short circuited within the cable because of the constant bending, most PSUs will shut down when they detect this condition - others will just die.

How competent are you with a Multimeter ? Is the Mains voltage making it to the PCB ? Near where the mains connects to the PCB there should be a large Electrolytic capacitor, you should measure around 340 - 380 DC on it's terminals - can you ?

Ken

gooch2k9

Is it 'chirping'?

nitna bitna

d.i.d electrical sell them for 22 quid

red sean

s the output cable ok ? They usually break where they exit the case or at the connector end. It's very possible that the + & - have been short circuited within the cable because of the constant bending, most PSUs will shut down when they detect this condition - others will just die.

How competent are you with a Multimeter ? Is the Mains voltage making it to the PCB ? Near where the mains connects to the PCB there should be a large Electrolytic capacitor, you should measure around 340 - 380 DC on it's terminals - can you ?

I'm getting 325 Vdc on the cap. terminals. I've disconnected the output lead and the output terminals are showing 19.3 Vdc which is what I expected.

Is it 'chirping'?

Kind of chirping sound now that the cable is disconnected. Is this ok? The problem appears to be at the jack end. Is that a suppressor coil just before the jack?

d.i.d electrical sell them for 22 quid

I wasn't looking to buy one as I already have a replacement. The cheap replacements are also one of the main causes of battery failure!

gooch2k9

It is chirping with the jack and lead off and you're getting the right voltage out of the terminals?

red sean

gooch2k9 wrote: »

It is chirping with the jack and lead off and you're getting the right voltage out of the terminals?

Yeah Gooch, although I've just put the cover on it now and I think the chirping may have been in my head! Would it be ok to take off the moulded coil and shorten the cable?
Thanks for all the help.
Sean

gooch2k9

The chirping tends to be very quiet, I had to put my ear to the casing on my own to hear it.

What coil are you talking about? Link a pic of it or something similar cos I've not had one with a suppressor on the DC output. I'd do a quick continuity test on the lead make sure it isn't shorting like Zener suggested, that's the problem I had.

red sean

It is shorting,I checked as Zener said, so I wondered if it was that coil at the jack end was causing it.
You can see it on this one beside the velcro strap:
http://charger.ie/home/2579-DELL-Inspiron-9400-Laptop-Charger-90W.html

gooch2k9

Hmm could be the insulation inside the cable has been frayed at some point it has been bent tight...I'd play around with the cable see if it can be set in some way that it isn't shorting before starting to cut things off.

My own I could see where the damage was so that is what I could do might be more awkward for you.

red sean

I have a charger here for something else that's not been used in yonks so I'm going to solder in the lead from that and see what happens. The jack happens to be the same. I'll let you know and thanks again for your help.
Sean

ZENER

Just check the output cables integrity. Especially near the charger itself. Actually, if possible cut the cable about 2 inches outside the charger and resolder it to the PCB.

The coil you mention is to eliminate RFI and provide a bit of filtering to the output and any other interference. There usually isn't much slack after it so cutting the existing plug off and soldering in a new one may be tricky. If it isn't possible then personally I'd cut the cable before the filter and solder in a new plug. This should eliminate all the usual stress points where a short or break could occur.

If you do decide to put in the other cable just check there isn't any damage in all these points mentioned in previous posts.

The chirping may have happened as you shorted and un-shorted the output as the cable moved, this is the switched mode frequency changing to cope with the load change.

Ken

red sean

Just to give ye heads up on this saga!
I replaced the lead completely and all is good now. I also had a Lenovo with the same problem but this was just the solder point on the pcb where the cable exits. All good now too.
Just embarrassed that I was caught thinking complicated when I always lecture young fellas to think simple when starting troubleshooting :mad:

Anyway thanks Gooch and Ken for your help and time!

Sean

ZENER

I hear ya Sean !! I worked with people who want to dive in with convoluted theories about a problem when in actual fact it's something really simple and basic ! I think we just doubt our own skills sometimes, don't believe that what we have spent years learning could possibly apply to any other situation.

Glad you got sorted.

Ken