Helikvar
Senior Member
Last Activity: 03-06-2025, 07:58 AM
Joined: 07-06-2018
Location: Pennfield
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With R21 removed and reading HVAA from C221 the voltage holds steady at 7.92v and IC5 no longer heats up.So obviously the load is the problem and not the chip.Does this mean it most likely is the panel and that's the problem . -
Have replaced all 3 caps and D18.Same symptoms as before .All voltages come on and hold steady except for HVAA which starts at 7.99v and seconds later drops to 3.45v
. IC5 still very hot over 102° C last time I read the temperature....Leave a comment:
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I did the ribbon method as well as the tape method also but only got one half screen black ,one half white and removing other ribbon all black screen .
. After studying the right control panel board attached to screen or tcon 2 as Dave put it I see that pulling either ribbon cable will disconnect HVAA from both panels and with the HVAA voltage going down to 3.4v the screen will never show a pic....Leave a comment:
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I tried the step below recently to see what would happen to IC5.(If it still got scorching hot)
. I noticed that L5,D18 and C31,C33,C34 formed a dc to dc buck convertor and thought that possible IC5 was providing the switching mosfet for the circuit.
. All the other coils have mosfets for switching power supplies with the gates controlled possibly from IC5.L5 doesnt have a descrete mosfet so I went with the presumption IC5 was doing the switching and wanted to see if IC5 would stop getting hot if I removed L5.
. With L5 removed IC5 stayed cool to the touch so that seems to...Leave a comment:
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[ATTACH]n3581929[/ATTACH] values are in this text file...Leave a comment:
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I already tried the 12v injection from main board to tcon board and rgb test begins but screen goes dark as soon as the HVAA voltage drops from 7.99v down to 3.34 v .I only see about 2 colors mostly yellow on entire screen but it quickly fades away .The backlights also come on and stay on....Leave a comment:
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Changed C221 and voltage on HVAA still drops down to 3.34v from 7.99v when powered on with remote after a few seconds.Leave a comment:
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Yes captcha eveytime and I agree very annoying.Checked all 0 ohm resistors and all read 0 ohm .Yes C221 is between HVAA test point and ground .It reads infinity when multimeter is on ohms .You think I should replace it even though it doesn't show its shorted.?
. Now to do another @#$$%# captcha.Leave a comment:
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The measurements on post 5 were taken from the tcon board which attaches to the mainboard/power supply..All other measurements taken from the integrated control board attached directly to the panel.
. The HVAA voltage reading is the same on both boards and the one causing the problem as it reads low at 3.3v as you pointed out.Leave a comment:
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Sorry the last pic was cut off on the ends I resized it to see entire tcon board.Leave a comment:
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Ok I've reduced one photo down to 2000 by 2000.Let me know if that is satisfactory and also any other photos you want me to reduce or retake at the requested resolution...Leave a comment:
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In circuitLeave a comment:
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D22 anode to cathode .233v leads reversed infinit
D16 anode to cathode .228v leads reversed infinit
D20 anode to cathode .228v leads reversed 2.69v
D18 anode to cathode .249v leads reversed 1.43v
D15 anode to cathode. 233v leads reversed infinit
Q3 drain to source .581v leads reversed infinit
Q4 drain to source .580v leads reversed 1.99v
Q5 drain to source 2.44v leads reversed .454v
Q3,Q4 p-CHANNEL mosfet
Q5 n-channel mosfet
T4 npn transistor checks ok
VGHF 28.1v
VGL_GOA -10.25v
VSS1 -8v
VIN 12.06v
...Leave a comment:
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Yes it is soldered to ground on both sides.Ok meaningless other than as a support....Leave a comment:
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With D13 removed the pads are still reading shorted .D12 reads shorted as well.D13 reads infinity in both directions perhaps I overheated it removing it .
. Strange thing is both the anode and cathode seem to be connected to the ground on both diodes which makes no sense.
There doesn't seem to be separate tracks for each only the common ground.Pics are included to show this .Leave a comment:
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D13 is reading short in both directions .I'll remove it and check diode off board to confirm whether it's D13 or the board itself.Diode is labeled SSL34BLeave a comment:
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The led blinking I was just using as a reference for when the HVAA voltage dropped from 8v down to 3.3v.
. The led blinks a total of 8 times whenever power cord is unplugged and plugged back in.But at the 6th blink that's when HVAA voltage drops down to 3.3 v.
. So its not a 6 blink trouble code it's 8 blinks every time power is restored to the mainboard /powersupply.When in standby mode led is red and when powered on with remote led goes out.
. I have gone over the ceramic capacitors several times hoping to find a shorted one and a quick fix but no such luck.So my guess is...Leave a comment:
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After searching the internet far and wide unable to find the chip ic5 on the right controller board.
. The chip manufacturer CHOT is also the lcd manufacturer so highly unlikely chip is available to the public
So unless I come across a cracked lcd panel with a good chip(highly unlikely)then I can't confirm the chip is the only problem but it does appear the chip gets very very hot and the HVAA voltage reduces precenting the lcd screen from coming on ..
. So I will leave it at that and at least that's some info if anyone experiences a no picture situation on this particular...Leave a comment:
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