Samsung 912N Problem

[LAS]

Re: Samsung 912N Problem

OK, thanks Retiredcaps. Back into the closet it goes.

[retiredcaps]

Re: Samsung 912N Problem

Can anyone tell me if the login card on the 712N is the same as in the 912N?

Even if they were the same logic card, there might be information inside the eeprom of the 712n that prevents it from working on a 19 inch monitor correctly? The resolution, refresh, etc might be not correct for a larger monitor?

[LAS]

Re: Samsung 912N Problem

Sorry, make that a 'logic card' in the above post.

[LAS]

Re: Samsung 912N Problem

Can anyone tell me if the login card on the 712N is the same as in the 912N? If so, I may be able to aquire one for a nominal amount.

[jetadm123]

Re: Samsung 912N Problem

Retiredcaps, I'm ok with the $4 and I'm ok with the soldering, but the reprogramming - any special equipment required?

LAS.

On the link I supplied above, check out post #56. Gonzo0815 gives a rough idea of what hardware/software to use.

[LAS]

Re: Samsung 912N Problem

Retiredcaps, I'm ok with the $4 and I'm ok with the soldering, but the reprogramming - any special equipment required?

LAS.

[retiredcaps]

Re: Samsung 912N Problem

Seems like this controller goes bad over time and the fix is to replace it and reload it's firmware. From what I can see, the success for this repair was pretty low.

$4 for an empty one, but then it needs to be programmed and the soldering looks a bit intimdating.

http://www.ebay.com/itm/270825016266

Well, it looks like you have some spare ccfls now to use for testing.

[LAS]

Re: Samsung 912N Problem

Well, the good news is that the monitor was given to me, and while I did change the caps, they can always be taken out and used elsewhere. Alternatively, the day may come when I come across another 912N and I can create my own 'Frankenstein' version out of the spare parts.

And the other good news is that my Blue ESR meter went together smoothly, and it's now complete. So I save these monitor parts for another day, and another monitor, and in the meantime I thank you all for your perserverence, help and extensive memories and experience.

LAS.

[budm]

Re: Samsung 912N Problem

Ah, that what I remember now! I know I see the symptom on other model before on this site, thanks for finding it, jetadm123.

[jetadm123]

Re: Samsung 912N Problem

While looking at your logic board photo, I noticed it had a Novatek controller, NT68F63L, which jarred my memory. Apparently, your logic board was also used on the 913N, which also had problems similar to yours:

https://www.badcaps.net/forum/showth...light=nt68f63l

Seems like this controller goes bad over time and the fix is to replace it and reload it's firmware. From what I can see, the success for this repair was pretty low.

[budm]

Re: Samsung 912N Problem

He measured at the Collector (PIN 9 of the connector) which is correct. If you have the 2 pins pointing toward you, the left pin is Base, the right pin is Emitter. The Collector has pull up resistor (R604, 10k), the transistor (NPN) is normally off which makes the Collect goes HI, when the controller send the positive signal to the Base, the transistor will turn on so the Collector voltage will go low.
That is, the BL_ON command output to the Base of Q601. So some how the controller chip tells the inverter to turn off when it gets the Video signal! The middle pin is Collector.
BL_EN HI = INVERTER OFF, Q601 turns ON, cOLLECTOR goes LO.
BL_EN LO = INVERTER ON, Q601 turns OFF, Collector goes HI.
You can force the Inverter to be on by connecting Base to Emitter.
See attached PDF for the transistor Q601, 2SC2412.
You will have to start checking the output of the voltage regulators, I see 3.3v, 2.5v, etc.

[jetadm123]

Re: Samsung 912N Problem

I suggested the collector because it's tied directly to the 9-pin connector. However, I see what you did. You measured the BL_EN voltage at the base, which is tied directly to the output of IC200, which is acceptable. It looks like the backlight is responding to the on/off commands. Sounds almost like the logic board can't handle the load when you plug in the video cable. Looking at the wiring diagram of the 9-pin connector, each pin has a voltage or ground associated with it. 14V, 5V. BL_EN, etc. I suggest you measure the voltage on every pin before you plug in the cable and again after you plug in the cable.

[LAS]

Re: Samsung 912N Problem

Budm and jetadm123,
When the monitor is turned on, with no video cable attached, the Q601 pin which is on a side by itself (I am thinking the is the base, not the collector, yes?) I get 3.7v. When I plug in the video cable, it goes to zero. If I unplug the cable and give it a few seconds, the backlights come back on and the pin goes back to 3.7v.

The transistor does not appear to be shorted out.

[LAS]

Re: Samsung 912N Problem

Thank you jetadm123. I have identified Q601 on the logic board, and I will test the one leg for hi / low and I will also test across the transistor for any shorts.

I have also found it on the schematic.

[jetadm123]

Re: Samsung 912N Problem

Hi Budm,

My logic board has no CN600...I took a look upthread at #22 where I posted a photo last week. It would have been right under the top left white multipin connector. Can BL_EN be checked some other way?

Looking at the schematic that budm supplied, you should be able to monitor BL_EN at the collector pin of transistor Q601. The collector pin is the side of the transistor with one leg coming out of it. Q601 is located directly below the white 9-pin connector on the logic board.

[budm]

Re: Samsung 912N Problem

We are looking for the HI-LO signal on this pin, if it changes when the monitor gets the video signal from the PC, then it is not the inverter circuits problem, it is just some how being told to turn off the backlights when the monitor gets the video signal, se we want to verify if that is the case.

[LAS]

Re: Samsung 912N Problem

I'll check Q600 right next to it for shorts. I missed that one while looking it over.

[LAS]

Re: Samsung 912N Problem

Hi Budm,

My logic board has no CN600...I took a look upthread at #22 where I posted a photo last week. It would have been right under the top left white multipin connector. Can BL_EN be checked some other way?

[LAS]

Re: Samsung 912N Problem

BL_EN is the one. See if you do have CN600 on the logic board, then see if the connector CN600 PIN9 has voltage reading, RED PROBE on pin 9, black probe on the chassis. Turn on the monitor without hooking up to pc so you cane see "CHECK SIGNAL" and read the DC voltage, then hook it up to PC and see the voltage again.

Service manual: http://elektrotanya.com/samsung_510n.../download.html

Very helpful Budm. I will check this tonight, and report back shortly thereafter.

[budm]

Re: Samsung 912N Problem

BL_EN is the one. See if you do have CN600 on the logic board, then see if the connector CN600 PIN9 has voltage reading, RED PROBE on pin 9, black probe on the chassis. Turn on the monitor without hooking up to pc so you cane see "CHECK SIGNAL" and read the DC voltage, then hook it up to PC and see the voltage again.

Service manual: http://elektrotanya.com/samsung_510n.../download.html