Re: No power (blackscreen) with MD3021PH -> AI-0088 the reason?
Hi alexanna,
thanks for the idea with changing position of T102 with T101. Will do that when I've got the new AO 4606 mosfets. Will take a while since I let them beeing shipped from hongkong.
knurz
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Last Activity: 02-21-2012, 02:51 PM
Joined: 01-27-2012
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Re: No power (blackscreen) with MD3021PH -> AI-0088 the reason?
Hello unique,
well because of your answer I became motivated again to test the HV transformers. T101 on the HV side (to LCD panel backlight) has 710Ohm, T102 has 705Ohm. The small 5 Ohm difference should be normal and indicates that the transformers are okay!
As I suspected, U101 has been roasted again and now short-circuit on every pin against each other pin.
Can you make something up for the rising sound after power-up? doesnt seem normal for me.
The small blue ceramic caps also...Leave a comment:
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Re: No power (blackscreen) with MD3021PH -> AI-0088 the reason?
Hello,
I did that so far, PlainBill. I resoldered almost every component in the mentioned area.
After that I replaced the broken U101 again and assembled the LCD. This time I got it working for several hours more than last time. But in the end the screen became black again.
I beg that it is U101 again.
I recognized a rising, high frequent but relatively silent beep/whistling-sound after each power up or changing the resolution.
But which part could cause that sound and...Leave a comment:
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Re: No power (blackscreen) with MD3021PH -> AI-0088 the reason?
Hello,
I did take a look, but the solderings don't look poor...Leave a comment:
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Re: No power (blackscreen) with MD3021PH -> AI-0088 the reason?
Unfortunatly I have to ask again for your help... As i mentioned above I replaced U101 & U105 and the LCD was working again.. But as I must experience, only for a short periode of time.
After that the screen became black again and no power sign.
So I disassembled again the LCD and took a look on the power board. I measured the resistance on the 4 AO4606 and again U101 seems to be short-circuit..
Before I replace the part a second time hoping for a longer time of sucess, I want...Leave a comment:
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SOLVED! Re: No power (blackscreen) with MD3021PH -> AI-0088 the reason?
Hello again,
today I could find the time to replace the mentioned ICs and assemble the LCD. The MD3021PH works now again like it has been for many years. Hope it will continue that again for a couple of years.
Thank you all for your support, especially PlainBill and retiredcaps!
Edit:
I just found out that the right name for this 19" LCD is MD3021[b]9[/b]PH. Maybe some mod/admin could change the Thread title that other users with the similar LCD and problem can get...Last edited by knurz; 02-08-2012, 05:52 PM.Leave a comment:
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Re: No power (blackscreen) with MD3021PH -> AI-0088 the reason?
Well first I will only replace U101 and U105. As soon as I did that I will test the LCD again. Hope I can give a positive report then
Thanks so far
Leave a comment:
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Re: No power (blackscreen) with MD3021PH -> AI-0088 the reason?
No I didn't. I just tested the voltages while power was on like Bill described in #4. I then was focused too much on the 'ticking' sound and thought I have to look for the reason somewhere else than with the AO 4606. Somehow I must have overread your first part of second sentence in #11.
Well I am still asking myself whether I should replace all 4 AO 4606 or just U101 & U105. Is it possible that U102 and U104 were also damaged during the short-circuit in U101?...Leave a comment:
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Re: No power (blackscreen) with MD3021PH -> AI-0088 the reason?
I understand, now we are really again on the beginning with the AO4606...
U102&104: from JP5 to GND R is about 2,24kOhm
U101&105: from JP12 to GND R is 0 Ohm
From JP12 to every Pin of U101 is 0 Ohm, seems to have a short-circuit
actually this seems to be the part which caused the brown spot an the board that i mentioned in the first post
After ur confirmation I will replace U101 & U105.
The other FET pair doesn't need to be replaced?Leave a comment:
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Re: No power (blackscreen) with MD3021PH -> AI-0088 the reason?
Hello PlainBill,
I did as u said:
D006 -> from each side lead to mid: raising resistance to more than 3,3kOhm -> should be no short
D007 -> from each side lead to mid: 0 Ohm -> short-circuit
D008 -> as mentioned in my last post, from IN to GND 0 Ohm -> short-circuit
After removal of JP28 and JP29:
Between every side and mid lead of D006, D007 and D008 there was a rising resistance to several kOhm while I was measuring.
The...Leave a comment:
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Re: No power (blackscreen) with MD3021PH -> AI-0088 the reason?
Hello again,
I unsoldered D006, D007 and D008 and performed a diode check.
I have got different values to the ones that displayed while still beeing in circuit.
[code]
D006
LT5207 SBL1060CT
+ - + => 186mV from each + to -
- + - => 1 from + to each - (no connection)
D007
LT5208 MBR10100CT
+ - + => 254mV from each + to -
- + - => 1 from + to each - (no connection)
D008
(no Diode...Leave a comment:
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Re: No power (blackscreen) with MD3021PH -> AI-0088 the reason?
Well unfortunately there is no english translation for the datasheet. But you are right, for voltages higher than 3V DC it will display the '1' for overload. The display shows the forwarding voltage in mV. For the D007 (MBR10100CT) it should be around 500mV for the low testint current.
Okay, I will do that and get D007 out. After that I perform the checks you mentioned.
On my AI-0088 board there is no D009. But the symbol is drawn on the diagram and there...Leave a comment:
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Re: No power (blackscreen) with MD3021PH -> AI-0088 the reason?
Thanks for explanation. I also took a look into the manual of the VC220.
I did a diode check for D006-D008:
[CODE]
D006
|>-*-<|
+ - + => 158mV from each + to -
- + - => 569mV from + to each -
D007
|>-*-<|
+ - + => 0mV from each + to -
- + - => 0mV from + to each -
D008
(no Diode symbol on board)
+ - + => 0mV from left + to -, 588mV from right + to -
- + - => 0mV...Leave a comment:
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Re: No power (blackscreen) with MD3021PH -> AI-0088 the reason?
@retiredcaps
It's the [URL="http://www.conrad.de/ce/de/product/121414/Voltcraft-VC-220-DMM"]Voltcraft VC 220[/URL] sold by Conrad Germany.Re: No power (blackscreen) with MD3021PH -> AI-0088 the reason?
@retiredcaps
It's the [URL="http://www.conrad.de/ce/de/product/121414/Voltcraft-VC-220-DMM"]Voltcraft VC 220[/URL] sold by Conrad Germany.Re: No power (blackscreen) with MD3021PH -> AI-0088 the reason?
@retiredcaps
It's the [URL="http://www.conrad.de/ce/de/product/121414/Voltcraft-VC-220-DMM"]Voltcraft...Leave a comment:
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Re: No power (blackscreen) with MD3021PH -> AI-0088 the reason?
Hhi clydeuk,
yes my multimeter has a audible diode checker. D007 definitely has a short-circuit between all pins, it's beeping and showing 0 Ohm.
D008 also has a shorted, but only from one side lead to mid.
So am I right and D007 (LT5208 MBR10100CT) is broken? What about D008?Last edited by knurz; 01-29-2012, 04:29 PM.Leave a comment:
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Re: No power (blackscreen) with MD3021PH -> AI-0088 the reason?
@PlainBill
Thanks for your instruction.
D006 (when u move along the "L" from top the first component on the heatsink) from each side to center lead: 2.23kOhm and 3kOhm
D007 (the next one on the "L" track): each lead has 0 Ohm
D008 (the last one and the one you were asking for; Designation is KIA 7812A PI 508): 8.3kOhm and 0 Ohm
What appeared strange to me, when I began measuring the resistance started around 300 Ohm and then increased until the given value limits!...Last edited by knurz; 01-29-2012, 03:57 PM.Leave a comment:
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Re: No power (blackscreen) with MD3021PH -> AI-0088 the reason?
@retiredcaps
Okay then I don't have to worry about that anymore. I tried starting to locate the evadable shortened diode but seems like it's quite hard. Some are parallel to resistors, some are connected with other parts..
D001 for example has 562Ohm in forward direction and 1664Ohm in reverse direction. At first view it looks damaged for me, at the second view I'm looking at the scheme and getting unsure whether that could be normal...
Should a shortened one have nearly no resistance in both...Last edited by knurz; 01-29-2012, 03:33 PM.Leave a comment:
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Re: No power (blackscreen) with MD3021PH -> AI-0088 the reason?
Hello,
the last thing PlainBill said, the 'ticking' sound, I can clearly hear that. It's very silent, but has a certain repeating rhytm. The times I checked the board I thought this was normal and doesn't mean anything.
I attached a mp3 of the sound. You have to increase the volume quite a bit until u can hear it.
It seems that is connected with the fluctuating voltages at GND and Pin6. I don't have the possibility of recording the peak and low voltage, but I could measure with my multimeter...Leave a comment:
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Re: No power (blackscreen) with MD3021PH -> AI-0088 the reason?
Hi
1) Yes, the voltages are actually fluctuating between the given values. (measured in DC mode). I assume that shoudln't be so?
2) Yes, R044 and R047 both have 27kOhm!Leave a comment:
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Re: No power (blackscreen) with MD3021PH -> AI-0088 the reason?
Hi,
between Pin 4 (GND) and Pin 6 is around 6-8V measured in DC, between Pin 4 (GND) and Pin 8 is around 200-300V DC. Measured with unplugged display but power supply connected to 'monitor' board via CN1.Leave a comment:
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