Repairing a FujitsuSiemens LSL3230T

[DMCrimson]

Re: Repairing a FujitsuSiemens LSL3230T

Well, I find it hard to believe those diodes were faulty after all - replaced them, plugged in, listened to chirping for a while and re-measured those 4 diodes with similar results. Any more ideas? Or should I just go and get a replacement unit if there's one available on eBay...

There was mention about startup cap - also that it rarely goes bad.

[retiredcaps]

Re: Repairing a FujitsuSiemens LSL3230T

Did you measure the diodes as I asked in post #18. Did you measure them out of circuit to verify?

[DMCrimson]

Re: Repairing a FujitsuSiemens LSL3230T

Nope, I should've done that though. If we start from assumtion that the diodes are indeed broken (again), what would you suggest is busting them?

[DMCrimson]

Re: Repairing a FujitsuSiemens LSL3230T

Now, that startup cap - would it be C803 (that yellow rectangular) MPXGMF40/100/21 metal film cap?

[Scenic]

Re: Repairing a FujitsuSiemens LSL3230T

Nope. The startup cap is normally a 35-50V 22-47uF electrolytic (somewhere in that range usually).

From the pic of the PSU board in the first post, I'd say the startup cap is C806 (right below the optoisolator and above the little PCB that sticks up)

[DMCrimson]

Re: Repairing a FujitsuSiemens LSL3230T

C806 is 10uF 100V and it's been swapped already...

[DMCrimson]

Re: Repairing a FujitsuSiemens LSL3230T

I'm beginning to wonder if the transformer itself is faulty - it has markings as follows:

SPW-134 A
E140167
LSE-B3 0839F3

clicking/ticking might be due to failing insulation, so if I was to replace it, what are the specs? Search over the net yielded nada.

[DMCrimson]

Re: Repairing a FujitsuSiemens LSL3230T

A month with no ideas... I'm thinking of sourcing a new PSU board.

Regarding that PSU, I'm wondering if I could use a different board - as long as the connectors are the same?

Oh, on other thread, Rusty informed me that the cap is 50V 10uF, but the one I have is 100V - would that matter?

[DMCrimson]

Re: Repairing a FujitsuSiemens LSL3230T

Managed to find a 50V 10uF cap, will need to try that tonight.

[DMCrimson]

Re: Repairing a FujitsuSiemens LSL3230T

Swapping that cap for a known good one didn't work out - the transformer still ticks. Could the resin inside it be failing?

[killian6pk]

Re: Repairing a FujitsuSiemens LSL3230T

Swapping that cap for a known good one didn't work out - the transformer still ticks. Could the resin inside it be failing?

Take ohms readings on the transformer. Pin 1 to Pin2; Pin 1 to Pin 3 etc. Until you have all the combinations of pin 1. Then start with Pin 2 and do the same and then on to Pin 3 etc. Number them any way you want. Just report back what readings you got. Remember power off.

[DMCrimson]

Re: Repairing a FujitsuSiemens LSL3230T

Primary side (AC) has 4 pins
measurements:
1-2: 0,2 ohm
1-3: ~5 Mohm
1-4: ~5 Mohm
2-3: ~5 Mohm
2-4: ~5 Mohm
3-4: 0 ohm

secondary side has 6 pins, but can be treated as 3 pins as they're soldered in groups of two:
zero all around.

[DMCrimson]

Re: Repairing a FujitsuSiemens LSL3230T

Could it be the feedback via opto? My neighbour told me the monitor ceased working all of sudden with no warning at all.

[wc_robot]

Re: Repairing a FujitsuSiemens LSL3230T

did you ever figure this out? I have the same problem on a Dell 21" LCD monitor, and the power board is almost identical to yours... same board number E131175 on the front, slightly different layout, few minor changes (e.g. 100uF 450V cap instead of 120uf 450V). I also tried replacing some components I suspected failing (the big cap, a few diodes on the AC high voltage side, etc), no luck.

Most significantly, when powered, mine is also clicking (about 100 times per second). I'm almost certain it's the yellow LSE-B3 transformer. When power is removed, it clicks at a rate directly related to the voltage in the large cap as it drops--slower and slower over about 10s while the big cap goes from fully charged (mine only gets to 164V) to empty. Due to the weird frequency of the clicking, I'm suspecting one of the smaller caps is charging up then the transformer shorts internally, and that cycle repeats.

My windings on side 2 are the same -- 0 ohms.
As for the 4 pins on side 1, i also get 0 ohms on 3-4, and 0.2 ohms on 1-2, but for all your ~5 Mohm values I have 148 Kohm

Let me know if you've solved your problem yet & how. If I can find a suitable replacement for this T, I'll try it out. Thanks!

[Rtech]

Re: Repairing a FujitsuSiemens LSL3230T

The integrity of this transformer,not this Model,but where it is in the circuit, has been questioned a number of times,NOT just for this board,but in many different ones.As far as I know none have been found faulty,and as yet after working on over 400 Monitors,I have yet to see one go faulty !!!.I have no schematic for this,but I suppose it will be pretty standard,and the secondary feeds Schottky diodes ??,and I would certainly take them out of the Board,a) to test them,and b)to power on with them out and see if the symptoms change.
I also suppose that there is a Mosfet fed by a SMPS chip,and if necessary I would also take that out,and this may help to check it :-
http://www.4qdtec.com/mostest.html

[DMCrimson]

Re: Repairing a FujitsuSiemens LSL3230T

Thanks Rtech. I'll need to check the diodes (did you mean those 1N4148's I already changed?) and the mosfet - thanks for pointers

wc_robot: There's an ongoing auction @ ebay, which has suitable board - I think that might be for you: http://www.ebay.com/itm/Hannspree-HF...8&cmd=ViewItem as the seller will only ship to states.

[DMCrimson]

Re: Repairing a FujitsuSiemens LSL3230T

Oh: would you tell the model of Dell monitor you have?

[Rtech]

Re: Repairing a FujitsuSiemens LSL3230T

The Schottky Diode, maybe more than 1, are NOT the 4148s, but will be mounted on a Heatsink, and it is probably the one nearest the Transformer.They are usually 3 leg devices,and the secondary of the Transformer will normally go directly to the outside pins on the device.

[DMCrimson]

Re: Repairing a FujitsuSiemens LSL3230T

Rtech: I've measured them earlier onboard, post #17, but will redo.

[Rtech]

Re: Repairing a FujitsuSiemens LSL3230T

Rtech: I've measured them earlier onboard, post #17, but will redo.

If they measured well, then take them out and then power on as suggested earlier and see what you get ref the clicking.