corintosh
Member
Last Activity: 01-26-2025, 08:50 AM
Joined: 12-20-2024
Location: Hamburg
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Alright I will give it a try. I am trying to learn as much as possible - could you explain your thought process behind this? I would have guessed the chip was out of the equation since we removed the path to it when RP831 was removed.... -
Thanks for staying on it with me!
The controller would be UP800? I will try it. I am still quite sure that when injecting voltage the very first time (still with RP831 on) it created a mark on it. Refering to post 76 in this thread....Leave a comment:
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Thanks, I do already use flex and the schematic for my board. I removed all caps that flex showed to be part of the lcd backlight out. This includes the ones next to the screen connector and the 4 on each side next to the main storage caps.
I included photos of the board with the caps taken off of all the regions.
If it is time to stop trying other things I will likely sell it for parts. I don‘t think it is worth to buy a replacement logic board as I probably would have to replace married parts....Leave a comment:
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Do you have another idea / anything I could try or check or is it time to assume the board is internally shorted?...Leave a comment:
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I should have included more info, it is already part of the ones I already uploaded. They are at the top....
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I hope the pictures show everything well enough. Flipping the side and measuring there gives the exact same values....
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Just checked your example, those should be the five caps next to the display connector CP600 - CP604. I compared my board to the boardview in flex and had all components in PPVOUT_LCDBKLT marked. The caps in there are all off. If there are other caps, that need to be removed they are still on.
Edit:
I also checked each pcb pad under my microscope after I removed the last caps and looked for solder bridges but there weren‘t any. If you want I can make some photos of the areas I removed the caps from. Maybe I am missing something.
If it is not a component...Leave a comment:
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Sure, that is completely fair.
Top side:
CP867 - CP873
CW194, CW195, CW196, CW18D, CW18B, CW18A
CP600 - CP604
Bottom side:
CP860 - CP866
CW18F, CW18E, CW18C, CW197
Also DP800 and RP831 are still off and CP810 and CW1A8 I removed earlier by accident. These are still off as well.Leave a comment:
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First of all thank you for your quick visit, flex and your videos. You are the reason I tried looking up what it could be in the first place, I did not know you are around here as well, what a lovely surprise.
I cannot thank you enough for your continuous support. Reading the original thread I thought „lets give it a try with this quality help, it might work“ and I sure learned a lot and had plenty fun.
I removed everything. There still is a low resistance path somewhere. At some point, while removing the last caps the resistance went down to...Leave a comment:
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I started removing caps and the first one directly seemed to add on to one low resistance path. It is a tiny 0201 resistor (CW196) and removing it immediatly increased resistance to 6.1 ohms.
I do not have a clue how much resistance there should be, so I would not know when to stop. It is probably safe to assume this did not resolve it and I continue removing caps?
As for the reassembly I will probably ask somebody more experienced to solder the 0201 and 0402 caps and can only put the bigger ones back. I also decided to buy replacements for all caps I removed because...Leave a comment:
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I checked every capacitor that is left in the backlight out multiple times injecting up to 3.5V. Nothing changed, no cap dried noticeably faster than the others (that is.. they all did not really dry at all).
When swapping the side I also swapped the probes by accident and therefore injected with the red probe to ground.. could this have caused damage?
The only thing I noticed after injecting voltage is that the resistance now is at 4.2 ohms so a tiny bit higher.
Do you still suspect the remaining 9 capacitors?, if so should I try it with even higher voltage?...Leave a comment:
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Thanks again for your ongoing help and patience, I like to think I am getting somewhat better at this but that would be all to you.
I can confirm the IC is isolated 150 kOhms at CP830 wrt ground. The LCD is disconnected, although the connector is still on the logic board.
I will check the boardview again to see which capacitors are left and try to find the short using voltage injection and alcohol. I will report back what I find (or don‘t find)
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I was able to remove it on the second try…
Still 3.7 ohms wenn measuring from ground to the pcb pads where the capacitors were.
Update: I checked the schematic again and figured it could be a capacitor next to JP600, using the microscope I saw some „spider web“ pattern on the bigger one and took it off.
The resistance now is 3.4 ohms…...Leave a comment:
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So I removed the diode and the resistance to ground with respect to the anode (upper pcb pad) is in the hundreds of kOhms and rising. The resistance to ground wrt the cathode is 3.6 ohms, so the same as before when we measured the suspicious capacitors.
I had a look which components could also lead to a short resistance path. It seems like there is a resistor (RP832) and some more very small capacitors that are possible candidates.
Thanks for your patience with me, how would you proceed now?Leave a comment:
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First of all, happy new year!
I doubt it is the meter but I cannot find any shorted capacitor, I took off the 14 capcitors from both sides and they all are okay. The resistance still is at ~3.7 ohms.
How would you proceed now?...Leave a comment:
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Just checked it and it fluctuates but always comes down to 0.1-0.3 before then randomly going up again.
I also just saw that there is a component missing that is in the schematics: CP830, it is already missing on the first picture and the board did not have previous work done....Leave a comment:
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The meter is in manual mode lowest possible setting, so it should be correct. You can review the attached picture. The resistance is equal on the empty pads.
I also attached a photo that suggests the caps are okay, they all read within the 2.1 and 2.25 uf....Leave a comment:
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I marked what I took off (again the other two capacitors were by accident...), I rechecked the other side and they look as clean as the remaining two on the side I worked on.
Resistance is 3.4 ohms. Would you advise me on removing more capacitors from the LCDBLT? Maybe the remaining two or the ones from the other side?
I still am confused by the mark on the backlight driver, should I wet the board with IPA and again inject voltage to see if it dries quicker on the backlight driver?
Thanks for your guidance!...
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Also, is there any way to figure out how much resistance I should measure in a healthy circuit besides having a second known good board?
I thought of removing more components of the backlight circuit but since I do not know what it should look like I wouldn‘t know when to stop.Leave a comment:
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Hey, I did remove the five rightmost capacitors and two smaller ones underneath them by accident…
For now I didn‘t attempt to put them back.
The resistance between ground and the removed caps still reads 3.4 ohms so it did not change very much.
I also saw this mark under the microscope that I missed earlier (see attached photo) it is also present in the pictures after the voltage injection (see the picture of my last post) but definitely was not there before.
Since this happened certainly when I injected the voltage, does this suggest the chip...Leave a comment:
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