Packard Bell CT700p shutting down

[Behemot]

I got this display which runs fine up to the moment whe in shuts down, which is usually after several hours of usage. It probably gets into some sleep mode because after turning off and on again it works fine for some time.

This display has external 12 V/4 A adapter. I measured the output, under usage there is around 0,3 V ripple which is quite high I think.

On the data and invertor boards are some small sized caps from brands unknown to me. Some of them seems to perhaps be bulging but it is almost unnoticeable, maybe thery are fine. Any idea what could be the problem?

[Th3_uN1Qu3]

Re: Packard Bell CT700p shutting down

Ripple on logic board supply can cause this. Also keep in mind that the inverter is directly powered by that 12v supply so it could be triggering an undervoltage condition. Try powering it from a computer PSU and see if it still shuts down, so you can narrow the issue.

[Behemot]

Re: Packard Bell CT700p shutting down

Good idea Will try my heavily recapped EuroCase

[Behemot]

Re: Packard Bell CT700p shutting down

I had to solder some wires on the board directly (it has the power connector built directly into D-Sub cable, on the graphics card side). It is taking the juice from the EuroCase PSU now, will let if for ~ 4 hours to see whether it will turn off or what.

[Behemot]

Re: Packard Bell CT700p shutting down

Still running so you probably had the point, thanks! Will open the adapter, recap what will be possible to, recap some of the caps inside display (using small caps laying on board) and eventually try to add some caps on input if that would be possible.

[Behemot]

Re: Packard Bell CT700p shutting down

Oh my f-u-c-k-i-n-g god! Kill the mutherfuckers making these adapters with fire on sight! I hate opnening them…

Anyway, there were two Chemi-Cons LXJ in paralel, 470 uF, just don't understand at all why for 50 V. Swapped them for LXZ 25 V/1000 uF, the ripple is now slightly over 100 mV. Now going for the small caps :-)

[Th3_uN1Qu3]

Re: Packard Bell CT700p shutting down

Sounds like they undersized the caps in the adapter from the get go, then normal aging took care of the rest. Larger value caps are probably all it needs.

[Behemot]

Re: Packard Bell CT700p shutting down

Yeah they used much higher voltage than needed and in this size (12,5x20 mm) they had lower capacitance. I used this 25 V/1000 uF with same can size, ordered from Digi-key together with D10 and D8 especially for displays where is small room usually :-)

[Behemot]

Re: Packard Bell CT700p shutting down

So I assembled the display correctly this time (first time I connected the cable from LCD the other way and gave one guy to test it, so it was gray all the time) and it is turning off once again after aproximately 50 minutes.

Any idea what to do next?

[Th3_uN1Qu3]

Re: Packard Bell CT700p shutting down

But, it does run properly on a computer PSU, right? Is the voltage delivered by the adapter lower than 12v?

[Behemot]

Re: Packard Bell CT700p shutting down

Well, it is 12,32 V under LOAD so definitelly the recap had some effect

[Behemot]

Re: Packard Bell CT700p shutting down

I kept the adapter opened and it's runnign for almsot two hours now. Maybe some strange overheatign related problem?

Well there is 12 V inside so I'll probably drill some holes in the plastic cover and add some small, slow fan :-)

[Th3_uN1Qu3]

Re: Packard Bell CT700p shutting down

I kept the adapter opened and it's runnign for almsot two hours now. Maybe some strange overheatign related problem?

Close the adapter, wire up a multimeter to it, and wait. See the voltage when the thing shuts down. Could be a substandard resistor somewhere.

[Behemot]

Re: Packard Bell CT700p shutting down

This is probably not it. I closed it and even if I did not watch the voltage till the end, it did not drop or rise at all.

The behaviour is strange because I would expect - if that would be normal overheating - when the monitor is turned off and on again, it should overheat much sooner because the adapter is hot at the moment, right? But it turns of again after almsot an hour, still quite the same time period.

[Behemot]

Re: Packard Bell CT700p shutting down

I found one broken zener on the output.

I currently have some canibalized zeners, is there a simple way how I could discover the voltage they are for?

[Behemot]

Re: Packard Bell CT700p shutting down

Diode is replaced, holes drilled, big one for fan cutted in, now the adapter is assembled and running. It's as cool as it wasn't running at all

[Behemot]

Re: Packard Bell CT700p shutting down

Here it comes again! Gonna kill it with fire.

Anyway. I think I have one adapter at home which should be compatible. Will interchange them and keep this one for, hell I don't know what But it could be of use to power something else, it's definitelly capable of 4 A of current, with the cooling I think it can do even more.

[Behemot]

Re: Packard Bell CT700p shutting down

Exactly the same behaviour with different power supply makes me believe there is something wrong in the display itself…

[Th3_uN1Qu3]

Re: Packard Bell CT700p shutting down

But, it does still work on a computer PSU, right? Check for any hyperactive protection circuits. At this point having a bench supply that is variable in fine amounts would be handy.

[Behemot]

Re: Packard Bell CT700p shutting down

Well, I had it completely open when I used the computer PSU so it could be some overheating inside the display, it was pretty hot when I opened it an hour ago. Trying to cool it with fan now, maby something will change.

I think we have some supplies here, will ask what exactly.

ADD// well, having the dispaly out of plastic cover with fan blowing on the metal cover, it is running fine for ten minutes more than usually :-)