HP LP3065 with partially failed PSU (USB works)

[beejay]

Re: HP LP3065 with partially failed PSU (USB works)

Somewhat good news (i guess). I tested the PSU alone today and it seems fine. Which could mean that the control board is at fault.

Here is what i did:

* Take the PSU board out and disconnect everything else.
* Connect 1kOhms from 5V to the STBN-24 which switches on the PSU permanently.
* Reconnect only the controll board (because the PSU needs some load on its 5V to work correctly)
* Supply 230VAC and see what happens.

-> The PSU is still cycling on-off-on-off ... i check the STBN-24 and it gets pulled down (from 5V to 0.3V) by the control board.

* I take out only the STBN-24 pin from the plastic-housing of the plug and reconnect PSU to control board
* Now there is no cycling anymore. I have this running for like 30 seconds. Stable 24V and 18V are being delivered.
* Nothing gets hot or smelly.

* Now i reconnect the other boards (STBN-24 is still NOT connecting to the control board)
* When supplying power the monitor still behaves "broken". The power led goes from green to orange after 3seconds and there is a little ticking sound every 5-6 seconds.

So ... the control board still thinks the PSU is not working and is cycling the power. This makes me think that the problem is neither located in the PSU nor in the inverter. Its likely to be on the control board or the TFT board. My next step would be to look at the signals and search for bad caps etc. on the PSU-section of the control board.

Any thoughts on this? Also, here are some pictures of the control board.

[beejay]

Re: HP LP3065 with partially failed PSU (USB works)

Now i found something interesting. In the picture below you can see the naming of the lines that go to the TFT-board. Among 4 times 18V there is one labeled PWR_ON and it cycles from 0V to 0.3V in that well known rythm. (by the way PS_ON is not connected by the cabling) Those 0.3V don't make any sense, do they?

What is this signal? Is PWR_ON the TFT board telling the control board that the power is good?

[beejay]

Re: HP LP3065 with partially failed PSU (USB works)

I traced the signal "PWR_ON" through the control board and it only passes 2 serial resistors and ends up at one of the microcontroller (NT68F63LG) pins at which it is down to 0.06V from 0.3V. On the TFT board it directly connects to a pin of some unknown 6 leg IC. (see closeup middle picture) It took 20min to get a good shot and i guess it sais "IAL BH". But even with the name i cant identify this thing. The black spot on the closeup is the "PWR_ON". It connects to the IC as well as via 1kOhms to +3.3V.

But maybe i dont need to know what that 6-leg creature is. As far as i can see, that corner of the TFT board should generate some new supply voltage. However all the lights are out there. No signals on those arrays of caps unless its the 18V supply power. Also nothing at the diodes.

Maybe the LM2717 (Dual Step-Down DC/DC Converter) is fried? Any other ideas?

[beejay]

Re: HP LP3065 with partially failed PSU (USB works)

At the moment i am a bit stuck and still trying to figure out what that 6-legged thing is (see above). Most likely name is "IAL BH". Does anybody have an idea?