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Old 10-09-2018, 07:09 PM   #22
Capt. Cap
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Join Date: Oct 2017
City & State: SF, CA
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Default Re: Another HannsG HG281D

Quote:
Originally Posted by momaka View Post
Sorry for the delay in response. My laptop from which I usually visit BCN decided to get corrupted HDD / Windows boot sector.
No worries, I hope you didn't lose anything Sounds like my typical week.

Quote:
Originally Posted by momaka View Post
Anyways.
Yes, if T-con is not getting power, then we need to look back on the logic board. T-con usually runs on either 3.3V or 5V. Follow the power pins on the t-con board going back to the logic board. Using this picture as a reference...
https://www.badcaps.net/forum/attach...2&d=1538959176
... you can see that there are 4 pins on the right side of the LVDs connector. After the first one, the next three have a trace that goes to fuse F400. Color-wise, those wires appear to be the just orange and red with the 3rd pin being unused. So follow these two orange and red wires to the logic-board.

On the logic board, there is likely going to be a PNP transistor or MOSFET that switches power to the T-con board. Using this picture uploaded by user Mishannya...
https://www.badcaps.net/forum/attach...3&d=1285531627
... and assuming your logic board is exactly the same (pictures of yours still wouldn't be a bad idea, just so we can verify), it appears that Q14 (8-pin SOIC chip) may be what switches power to the t-con. Because I can't see if that is 100% true, use your multimeter's continuity/lowest resistance setting to find what switching component these two orange and red wires on the LVDS connector connect to. If it's a PNP transistor, it may have gone open-circuit. If it's a MOSFET, it may have a Gate shorted to ground, which won't allow it to turn on.
I'll check resistances on Q14 tonight, see my reply to budm for voltages.
I have v6.0 of the board, it's mostly the same but seems to have less parts populated, pictures are pending.

Quote:
Originally Posted by momaka View Post
The issue could also be that this switching part is not getting a signal from the main controller to turn on. In that case, we will have to investigate what exactly controls this t-con power switch and why it is not getting a turn on signal (for example, it could be that the bad caps on the t-con caused too much noise and corrupted the flash chip, which then doesn't allow the main controller to boot and run everything else... though that's unlikely.)
The CCFL switches on and off at the appropriate times when the computer starts / stops sending video to the display, so something is getting signalling from somewhere, though I don't know how much logic board is involved in kicking the CCFL on and off.


Quote:
Originally Posted by momaka View Post
All of my cheap red Harbor Freight multimeters are like this. I still use them a lot, though.

If that's not the issue, you may need new probes then.
Lol, how did you know?
Yep, it's a cheap (free) red Harbor Freight multimeter, in this case the problem turned out to be a loose wire in the ground probe - jiggling it causes the resistance to jump around.

I just used another I had in a drawer for recent measurements, probe-to-probe resistance on that one was 0.8 Ω, F400 looks totally fine when using it 👍

Can't have too many multimeters.
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