Repairing a FujitsuSiemens LSL3230T

[DMCrimson]

Victim/patient in question is a 23" FullHD display sporting a LG-Philips LM230WF1-TLA1 panel, dual HDMI and one VGA input. The previous owner simply said there's no picture, which leads to CCFL-problems first.

Interestingly, the power supply board is the same as used on Hannspree HF237HPB - and has faulty caps (SamXon - bulged, Lelon, Su'scon) - for which I've already purchased replacements (Hitano EXR) and intend to replace as soon as I can get my troubles with Weller sorted out...
Here are the questions though:

1. The PSU is mounted face down, so that the leads on the left side go to the driver PCB, but the previous owner had removed them - are they 1-on-1?
2. U101 on the driver PCB has markings 1084-33 0825FL - from what google tells me that's a 5A low-dropout regulator, 3.3V - is that right?
3. Is that driver PCB used elsewhere? The board in question is ILIF-114.

[retiredcaps]

Originally Posted by DMCrimson

U101 on the driver PCB has markings 1084-33 0825FL - from what google tells me that's a 5A low-dropout regulator, 3.3V - is that right?

Yes.

[DMCrimson]

to continue problem #1: the cable shown attached to the PSU board has no connector on other end, just bare crimped ends - are these connected to the driver board in the same order as they are on the PSU?

[PlainBill]

Originally Posted by DMCrimson

to continue problem #1: the cable shown attached to the PSU board has no connector on other end, just bare crimped ends - are these connected to the driver board in the same order as they are on the PSU?

Usually. There are things you can do to make sure. One major one is to check that all ground pins match. Another is to make sure 5V pins match.

PlainBill

[DMCrimson]

Thanks for the pointers - need to fire that multimeter up later tonight

[Scenic]

Originally Posted by DMCrimson

to continue problem #1: the cable shown attached to the PSU board has no connector on other end, just bare crimped ends - are these connected to the driver board in the same order as they are on the PSU?

Sounds like the previous owner has some explaining to do. He probably ripped the crimped connectors out of the plastic part of the plug and lost the plastic part (i.e. he's been in there before, most likely not telling you about it)

[DMCrimson]

He sais he'd opened it, but when I asked about the said connector he had no recollection there being a connector - but then again, I'll be measuring stuff tonight

[Scenic]

Having the crimped connectors loosely sitting in there would make it ridiculously easy to short out. I highly doubt it came like that from the factory.

If you're lucky, the backside of the controller board might have some indications as to which pin is what (like the PSU board above the connector in the pic in post #1)

[DMCrimson]

Well, took a bit time, but the grounds line up on controller board the same way as on power supply - so do 5V's. Now I just need proper connector housing...

[DMCrimson]

Found suitable connector from some oldish 4:3 BenQ-tft - although it's a bit too wide, being 12-pole instead of 10-pole, so I'll need to cut it a bit...

[DMCrimson]

Time to bring this up again Today I finally had time to put this thing back together - and as you might guess... It's not powering on - those 5V lines that go to the driver board have only ~2V and the transformer in the middle of the PSU board makes some ticking noise -faulty?

[Jasgriff]

I am not massively sure that I am on the right track here but I think it makes a noise when there is not enough power to drive it?

You could try testing the main filter cap and see what voltage you have running across that to see if its right or not.

[DMCrimson]

If you mean by main filter cap that huge one, it had some 300+ volts over it.

[tom66]

Startup cap or bad diode on secondary.

[DMCrimson]

D806 is SRF 10-20 and D807 is SRF 10-10 - how would I measure them? Or rather, what readings they should give without power...

[Jasgriff]

You need to put your meter on the ohm setting and read then both ways around. Make sure its done with the power off.

You should have a low reading then a high one. If you get 2 very low or very high readings then they have gone.

Let us know your readings.

[DMCrimson]

Here are some measurements I've already done:
D2: 0,547 V
D4: 0,546 V
D8: 0,545 V
D9: 0,549 V
ZD801: 0,645 V
D802: 0,474 V
D803: 0,442 V
These were measured with meter set to diode.
D806: ground in the middle, readings 0,337 V left and right (ohms:3,847k right, up to 23k left - stabilizes around 17,5k)
D807: ground in the middle, readings 0,248 V left and right (ohms: 1,927k right, up to 23k left - stabilizes around 18,5k)

Will measure the DC across the big cap later - my kid is still awake...

[retiredcaps]

Originally Posted by DMCrimson

Here are some measurements I've already done:

To test a diode using the diode test function, you must take 2 readings on the same diode. One reading is with the probes one way and the second reading is with the probes reversed.

A good diode should read between 0.3 to 0.8V and "out of range" the other way.

[DMCrimson]

Have yet to measure them the wrong way round - they do look proper the right way

[DMCrimson]

Indeed - there were 4 faulty ones:
D2: 0,766 V
D4: 0,767 V
D8: 0,767 V
D9: 0,766 V
Going to replace them tomorrow. I think I have a hundred of those (1N4148) stashed or so