Samsung 930b LCD cold start problem (inverter?)

[Logicsays]

Re: Tech details on green fuse?

Can we clear and focused picture of YOUR boards? Referencing other people's pictures doesn't help us diagnose YOUR problem. Your board could have unique characteristics not shown in someone else's photo like a charred resistor or suspicious looking transistor.

It is not uncommon for manufacturers to make changes on their boards. Also try to get the resolution as close to 2000x2000 as possible.

Sure.. I'll get a snapshot asap. I have a great camera so I'll post a nice big highly detailed pic. Thanks for your help.

[retiredcaps]

Re: Samsung 930b LCD cold start problem (inverter?)

The image is viewable with a flash light.. so something is working..

Some inverter board sections have a fuse and it could be open. Or it could be a shorted mosfet or transistor in the inverter section. These components could be on the backside as well and you will need a multimeter to test them.

[retiredcaps]

Re: Samsung 930b LCD cold start problem (inverter?)

I replaced the three bulged caps.. no change.

BTW, most members here including PlainBill would suggest changing all the capacitors except the largest one which rarely, but not never, fails.

Capacitors die from age, heat, and shoddy build quality. Capacitors DO NOT have to be visibly bloated in order to bad. They can be out of tolerance uF (a 1000uF measures 20uF) and/or have high ESR (ohm). A multimeter will be insufficient to test for ESR. For that you need an ESR tester which costs between $50 and $300.

[alexanna]

Re: Tech details on green fuse?

Can we get clear and focused picture of YOUR boards? Referencing other people's pictures doesn't help us diagnose YOUR problem. Your board could have unique characteristics not shown in someone else's photo like a charred resistor or suspicious looking transistor.

It is not uncommon for manufacturers to make changes on their boards. Also try to get the resolution as close to 2000x2000 as possible.

Just another sugestion.Samsung boards are very good about identifying voltages on the connector from the power supply to the logic board.
It would be a good idea to verify these, including the backlight on signal.

[EGuevarae]

Re: Tech details on green fuse?

Can we get clear and focused picture of YOUR boards? Referencing other people's pictures doesn't help us diagnose YOUR problem. Your board could have unique characteristics not shown in someone else's photo like a charred resistor or suspicious looking transistor.

It is not uncommon for manufacturers to make changes on their boards. Also try to get the resolution as close to 2000x2000 as possible.

And why only the bulged caps? Caps can go bad even when not bulged (low capacitance or high ESR...).
Replace them all as a rule and you'll save time .....

[Logicsays]

Re: Samsung 930b LCD cold start problem (inverter?)

Well, I'm no expert on electronics. I learn quickly but I was following this thread from the start and i replaced the caps. Others mentioned the fuse being problematic so I was looking for it to test it.

I did the whole power on and check with a flash light. I see the image so something is working right. I still will take some pics if I ever get some time.. been really busy fixing computers.

I think I found the fuse under a glob of rubber stuff. I'm going to check it out and see if its tests good. A friend of mine repairs defective Toyota ECM's so I might have an in on some help.. lol

[rico_st]

Re: Samsung 930b LCD cold start problem (inverter?)

Hi to all!
I have Samsung 930BF and have problem with backlight. I replaced all caps and picofuse but still no backlight. Any idea where else to look?
Here are pictures of my board.
Thanks!

[Rtech]

Re: Samsung 930b LCD cold start problem (inverter?)

More detail on 'problem with Backlight', would certainly help,to allow members to maybe help you,eg None work,they work sporadically, they go on and go off BUT Power light stays on etc etc etc.

[rico_st]

Re: Samsung 930b LCD cold start problem (inverter?)

Hi!
Problem is that backlights arent working at all.Power light is on. I replaced 3 bad CapXon 820uF 25v caps with 1000uF 35v and others 2x100uF16v,1x330uF 16v, 1x10uF 63v, 1x47uF 63v. I replaced them with new "JAMICON" caps. Replaced picofuse with litle wire.You can see picture but still no backlight. Where else to look?
Thanks!

[PlainBill]

Re: Samsung 930b LCD cold start problem (inverter?)

Hi!
Problem is that backlights arent working at all.Power light is on. I replaced 3 bad CapXon 820uF 25v caps with 1000uF 35v and others 2x100uF16v,1x330uF 16v, 1x10uF 63v, 1x47uF 63v. I replaced them with new "JAMICON" caps. Replaced picofuse with litle wire.You can see picture but still no backlight. Where else to look?
Thanks!

Measure the ON/OFF and A-DIM pins on the connector. ON/OFF should be about 3.3 volts, A-Dim will probably be lower, around one volt. If these are correct, trace the signals from the connector to the inverter controller. Check for proper voltages at the inverter.

Tip: You gave us good pictures of the top of the board. An equally good picture of the bottom would help us help you.

Tip 2: A fuse is placed in a circuit to protect components in case of an overload. Substituting a wire for a blown fuse without verifying the cause of the blown fuse has been eliminated often leads to more expensive and expensive repairs.

PlainBill

[rico_st]

Re: Samsung 930b LCD cold start problem (inverter?)

Measure the ON/OFF and A-DIM pins on the connector. ON/OFF should be about 3.3 volts, A-Dim will probably be lower, around one volt. If these are correct, trace the signals from the connector to the inverter controller. Check for proper voltages at the inverter.
......
PlainBill

Hi!
My knowledge about electronic isn't too good but i measured it on the back of the board. On/OFF 0v, A-dim 0v, 5v and 13 are ok.
(i measured it without connected videoboard?)
Here are pics of the back.

[Rtech]

Re: Samsung 930b LCD cold start problem (inverter?)

The A-Dim and On/Off are supplied by the video board,so you need to,have it connected to the PSU/Inverter,and then you need to arrange the Monitor to be switched on,with the VGA lead connected and your PC switched On.There are other ways but this is maybe the best way for you.When your Front panel lamp shows the PC signal has been recognised, then you should be able to measure the A-Dim and On/Off voltages.

[rico_st]

Re: Samsung 930b LCD cold start problem (inverter?)

Ok!
I conected videoboard and power board (without lamps and panel) video cable to pc and turn on pc and monitor and measured On/Off 2.37v, A-Dim 0.01v.
Is that ok?

[Rtech]

Re: Samsung 930b LCD cold start problem (inverter?)

Ok!
I conected videoboard and power board (without lamps and panel) video cable to pc and turn on pc and monitor and measured On/Off 2.37v, A-Dim 0.01v.
Is that ok?

No problem, the Dim voltage varies depending on where the OSD level is set, BUT the on/off voltage should have turned the Lamps on, so plug them in....

[rico_st]

Re: Samsung 930b LCD cold start problem (inverter?)

No problem, the Dim voltage varies depending on where the OSD level is set, BUT the on/off voltage should have turned the Lamps on, so plug them in....

Nothing
Still no backlight. Lamps are gone?

[Rtech]

Re: Samsung 930b LCD cold start problem (inverter?)

Maybe, but measure the resistance of the secondaries of both of the Inverter transformers, they should be very very similar measurements.

[rico_st]

Re: Samsung 930b LCD cold start problem (inverter?)

Thanks for yor effort helping me.
I measured resistance in transformers secondaries (onboard) and they are similar. 1.32 and 1.35. They are ok? What else to check?

[Rtech]

Re: Samsung 930b LCD cold start problem (inverter?)

Well, looks like Last Chance Saloon,before the Backlights become the Main suspects,so I would resolder the Inverter transformers,and all other joints between the secondary and the Lamp sockets,eg the small Blue Caps etc etc.

[rico_st]

Re: Samsung 930b LCD cold start problem (inverter?)

No luck
I will risk 20$ and buy new(used) power board on ebay.
Thanks!

[Rtech]

Re: Samsung 930b LCD cold start problem (inverter?)

Waste of money if its the Backlights !!!!