Electronics > Repair

Sharp LJ320U27 EL display, looking for any help


I am trying to repair Sharp LJ320U27 electroluminescent display. Display is part of control unit of big sheet metal folding CNC machine, and that machine is almost useless without it.
I can not find any useful information on web, all I can find is datasheet but it only contains mechanical data.

I am looking for pinout (I figured out supply pins) and possibly data protocol info.

Display is completely dead. I suspect on HV supply failure, but don't know if display needs to be initialized to start it...

I'm trying to fix this too, but I don't have too much information.
The attached document was obtained from the Internet, and the document has two pages.
Ask whoever has the rest of this document.
Thanks for sharing.
The machine I have is a RION KH-02A.
+15V (pin1,2) is being checked because F2 Fuse (630mA) is short-circuited, but there is no circuit diagram.
+5V (pin3,4) is F1 Fuse (500mA) is normal.
In addition, I would like a lot of advice from someone who has experience in repairing this ELD Display.

There is some info on the input signals and pin numbers here: http://www.vabolis.lt/stuff/LJ640U35.pdf

The F2 Fuse (630mA) was replaced with a socket attached to 1A, and C29 (10V, 470uF), C30 (10V, 47uF), and C36 (35V, 100uF) were replaced because there was a leak.
After assembling, there is no reaction in power ON and ELD.
If you press Re-set of CPU Board, ELD blinks. And then there is no response.
If you measure +15V (pin1,2), it goes down to +3.9V.
+5V (pin3, 4) is normal.
Guessing, I think T1 (high voltage Trans) is normal. (Flickering is proof of that?!)
The thing I suspect is IC4 (IR3M01, 16pin, Switching Regulator Control Circuit).(?!)
I measured the current of the PSU to find the +3.9V drop. (The label says that +15V is 0.65A, +5V is 5A).
The measured value is 6.6A for +5V and 0.9A for +15V.
So the PSU is considered normal.
At this point, the circuit diagram is desperately needed.
Can anyone share a service manual?
Thanks a lot for your advice.

As shown in the attached picture, I removed CN1-4 connected to the board from the display and tested it, but again, +15V is lowered to +3.9V.
So, I cut off the +15V pattern line going into T1 (high voltage transformer) and turned on the power again, but it is still lowered to +3.9.
(As the situation progressed to this point, it also made me think that it is normal for the voltage to be lowered. If the voltage is lowered, IC4 cannot be driven.)
Now all that is left from the +15V supply is IC4, C8 (35V, 100uF, ok), D2 (Zener, ok), RA2 (10K, pin3 to 1, ok), TR1 & 2 (2sk739, N-Channel FET, short Since it did not work, it is judged as normal)
Now, as a final decision, I decided to replace the IC4 and applied for 5 units of $10 to Ali.
If you have any advice on the process I'm going through, I'll listen to anything.
Thanks a lot for your advice.
If +15V is lowered to +3.9V even after replacing IC4, the cause is somewhere else.
(If you look at the picture, you can see the photo coupler, PC1 & 2, and also the black mod chip, but the situation is complicated. The fact that there was also a bad line pattern contact in the electrolytic capacitor 10V, 470uF, which was replaced with a leak before, leads to the failure of many parts. Makes me think.)
Therefore, if it fails to replace IC4, it is concluded that it cannot be touched for a long time.


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