Author Topic: Need help fixing my computer screen. Capacitor values?  (Read 1120 times)

0 Members and 1 Guest are viewing this topic.

Offline tcz

  • Contributor
  • Posts: 19
  • Country: ca
Re: Need help fixing my computer screen. Capacitor values?
« Reply #25 on: April 20, 2021, 05:41:04 am »
I have a confession to make...

10 years ago, I sold a 100mhz HP Agilent Oscilloscope for 100$ or maybe it was 150$ either way I thought I would never learn electronics enough for it to ever be useful.

I am so very angry with myself.  |O
« Last Edit: April 20, 2021, 05:42:54 am by tcz »
 

Offline tcz

  • Contributor
  • Posts: 19
  • Country: ca
Re: Need help fixing my computer screen. Capacitor values?
« Reply #26 on: April 20, 2021, 06:03:54 am »
I was just able to confirm that the LED back light AND the LED driver board are working by turning them on.

I did it by shorting the 3.3 volt pin to the ON/OFF pin on the cable that connects the power supply to the control board.

So the Interface board definitely IS the culprit.


I also did another potentially "stupid" thing; since I couldn't find proper diagram for TSUMU58EHJ-LF-3 and setting pin 27 low did nothing, I tried setting low other pins, tried all of them one by one. Maybe I fried it who knows.

I was able to find 3 pins that send the monitor in standby and then off, but I cant turn it on again until I reset the monitor (dis/reconnect power), then I can do it again as many time as I want.

Could this indicate the TSUMU58EHJ has some life in it? and from this can we imply that the crystal is fine? (otherwise the chip would not run at all right?)

I'll be back later, I gotta go clear my head by performing various voodoo rituals around the board...   :scared:



« Last Edit: April 20, 2021, 06:09:15 am by tcz »
 

Offline ebastler

  • Super Contributor
  • ***
  • Posts: 3879
  • Country: de
Re: Need help fixing my computer screen. Capacitor values?
« Reply #27 on: April 20, 2021, 06:51:06 am »
Here is a a close up of the OZ99xx chip and the transistors.
Are those holes on the transistors??? They all look the same except for one that doesn't seem to have a hole in the "dot" of the marking.

Nobody has apparently commented on this yet -- but yes, that does look like holes burnt into the SOT-23 package to me. While I have not personally seen this in SOT-23 transistors, I have encountered SOIC packages with very similar-looking small holes after they had let out the magic smoke. Given the fact that more than one transistor is affected, some other root cause has probably triggered their failure.

Or am I misinterpreting this? Has anyone come across similar "holes" which were benign?
 

Offline Jwillis

  • Super Contributor
  • ***
  • Posts: 1019
  • Country: ca
Re: Need help fixing my computer screen. Capacitor values?
« Reply #28 on: April 20, 2021, 07:12:50 am »
I was just able to confirm that the LED back light AND the LED driver board are working by turning them on.

I did it by shorting the 3.3 volt pin to the ON/OFF pin on the cable that connects the power supply to the control board.

So the Interface board definitely IS the culprit.


I also did another potentially "stupid" thing; since I couldn't find proper diagram for TSUMU58EHJ-LF-3 and setting pin 27 low did nothing, I tried setting low other pins, tried all of them one by one. Maybe I fried it who knows.

I was able to find 3 pins that send the monitor in standby and then off, but I cant turn it on again until I reset the monitor (dis/reconnect power), then I can do it again as many time as I want.

Could this indicate the TSUMU58EHJ has some life in it? and from this can we imply that the crystal is fine? (otherwise the chip would not run at all right?)

I'll be back later, I gotta go clear my head by performing various voodoo rituals around the board...   :scared:

That's awesome ! I would say that the main board is the problem as well. I looked into those universal boards and if you search the on board chip NT68676 you'll find various info on it. Unfortunately I didn't come across any data sheet . 
I found this for you M.NT68676.2A
You can find just the board in different versions for your LCD display. But if your back light is working you won't need the CCFL inverter board .


Here is a a close up of the OZ99xx chip and the transistors.
Are those holes on the transistors??? They all look the same except for one that doesn't seem to have a hole in the "dot" of the marking.

Nobody has apparently commented on this yet -- but yes, that does look like holes burnt into the SOT-23 package to me. While I have not personally seen this in SOT-23 transistors, I have encountered SOIC packages with very similar-looking small holes after they had let out the magic smoke. Given the fact that more than one transistor is affected, some other root cause has probably triggered their failure.

Or am I misinterpreting this? Has anyone come across similar "holes" which were benign?


The LED driver board was confirmed to be operational and the transistors were confirmed to be working as well . 
 

Offline tcz

  • Contributor
  • Posts: 19
  • Country: ca
Re: Need help fixing my computer screen. Capacitor values?
« Reply #29 on: April 22, 2021, 09:24:44 pm »
Quote from: Jwillis
Here is a a close up of the OZ99xx chip and the transistors.
Are those holes on the transistors??? They all look the same except for one that doesn't seem to have a hole in the "dot" of the marking.

Nobody has apparently commented on this yet -- but yes, that does look like holes burnt into the SOT-23 package to me. While I have not personally seen this in SOT-23 transistors, I have encountered SOIC packages with very similar-looking small holes after they had let out the magic smoke. Given the fact that more than one transistor is affected, some other root cause has probably triggered their failure.

Or am I misinterpreting this? Has anyone come across similar "holes" which were benign?


The LED driver board was confirmed to be operational and the transistors were confirmed to be working as well .

I'm glad I'm not the only one wondering about theses. Gotta admit it's strange to find what looks like holes on top of transistors. BUT it's true that the driver works, I was able to light the whole panel in a very bright white and Jwillis says the transistors reading I took looked good so I guess it's either normal or some form of aging that is not critical yet?

About the M.NT68676.2A controller, I was looking at the exact same one. I was finally able to find a seller that understood what I was talking about and he sent me a document (attached) with specifications, schematics and pin out info.

He has a compatible LED driver for me but their controller board requires an external 12v 4A power source and I would rather keep it internal.

If I find 12v on the current power supply can I just connect to it to power their controller?
If not is it OK to power it using a step down circuit from eBay on the 18v line to the driver board?

I also wonder if their LED driver will be as bright as the current one.
Preserving the current PS would make it easier to use the original driver, using an external PS would require stepping up the 12v to 18v for the driver.

Also, are we sure the "DIM" signal from the new controller is the same as the original "BRI" signal? Same thing for the ON/OFF signal.

Back to some more  :scared:



 

Offline wizard69

  • Frequent Contributor
  • **
  • Posts: 833
  • Country: us
Re: Need help fixing my computer screen. Capacitor values?
« Reply #30 on: April 25, 2021, 09:37:15 pm »
One thing to consider is after removing all of those caps I’d be very reluctant to put them back in.   By doing so you have just put them through another soldering thermal cycle plus the mechanical stress of disassembly.  It just is t something I would not do on a power supply.     More importantly I wouldn’t have removed them before checking the supply. 

As for the backlight I’d consider the driver in the same way.  Check it’s output.   That is if you can easily, backlights are becoming increasingly more complicated.  In the simple ones anyways you have inputs and outputs that should be easy to figure out.   

 


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf