Re: Another HannsG HG281D
I was looking at the power supply board with a magnifying glass, forgot it was still plugged in running in standby mode, and accidentally touched the metal frame of the magnifying glass across some pads or traces on the back of the board on the low frequency side.
I heard a bzzzzzzzzzzzzt, quickly moved the magnifier away, but it no longer kicks on.
I get the orange and blue LED power standby lights, but when it tries to turn on, I just hear a quick, faint ticking noise coming from the power supply.
:facepal...
Capt. Cap
Member
Last Activity: 10-25-2018, 12:27 AM
Joined: 10-03-2017
Location: SF, CA
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Re: Another HannsG HG281D
I checked [URL="https://www.badcaps.net/forum/attachment.php?attachmentid=182491&d=1536701504"]BUF07704[/URL] and got similar results to what [URL="https://www.badcaps.net/forum/showpost.php?p=850402&postcount=32"]rrflorida mentions[/URL].
U301 has INCOM of 0V, OUTCOM starts at 5V and climbs to 9.77V.
U300 has INCOM 5.47V, OUTCOM 5.55V steady which looks more normal.
Could I also have a failed BUF07704?
Though looking closely at the traces, it seems like INCOM and OUTCOM of U301 could...Last edited by Capt. Cap; 10-17-2018, 01:31 AM.Leave a comment:
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Re: Another HannsG HG281D
Turns out it's not the ribbon cable
I got the idea to swap the two cables, and the right side of the display still works with the cable I thought might be bad, and the left side of the screen is still not displaying any picture with the known good cable.
I guess the tab bonding board is next to check?
Or could it still be a TCON issue?Leave a comment:
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Re: Another HannsG HG281D
Thanks for taking a look!
That's relieving to hear! Earlier today, I did Tom's T-CON board diagnosis spreadsheet [URL="https://www.badcaps.net/forum/showthread.php?t=45378"]mentioned here[/URL], and it had gotten me worried as it showed my VDDA as a Marginal/Fail, and "VCOM given to AVDD" (whatever that is) as an outright fail. But then again, it showed my VGL as failed also even though is was dead in the middle of the -5 to -15V range, so I guess should be taken with a grain of salt.
...Leave a comment:
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Re: Another HannsG HG281D
Heh, I thought that might be the case, but your comment also made some sense since you pointed out the logic board is made for a 12V display and the panel is 5V....Leave a comment:
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Re: Another HannsG HG281D
Regarding this ribbon cable on CN501, it is very finnicky - if I don't leave it with a little pressure holding it just right, the right side of the display goes from normal to faded and discolored.
What is weird is that this ribbon cable should be effecting the left side of the image displayed, since the cable is the one on the right side of the TCON when viewed from the back. Or am I completely off here?
I sometimes got lighter grey horizontal rectangles, about a half inch high and spanning the entire left side of the monitor...Last edited by Capt. Cap; 10-13-2018, 06:27 PM.Leave a comment:
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Re: Another HannsG HG281D
Some more good news!
I removed FB14 and soldered in some copper wire across it, and got a consistent image on the right side of the display.
By gently pressing around on the ribbon cable at CN501 (right side of the TCON), I can nudge it into a position that yields a normal image on the right half of the display
I took readings from almost every test pad and some other places of interest on the TCON while the right side image was good, hopefully it can help determine if the TCON is OK and the problem lies downstream....Leave a comment:
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Re: Another HannsG HG281D
All of these parts are original with my HG281D. The logic board / TCON / display combo is what was slapped together at the factory.
Some fine HannsSpree engineering for you there
...
Leave a comment:
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Re: Another HannsG HG281D
I was poking around the circuit boards again today, and when I checked the front of the screen, on the right half of the display, a sort of faded, discolored image was showing!
I took all new TCON measurements (numbers look much better), had the computer go back to sleep while doing so, and when it kicked back on, the screen was all white again.
Voltage was sagging back to 2V at Q14 source, I started poking around on the 5V line, and noticed that the right hand side of the display flashed when I touched...Leave a comment:
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Re: Another HannsG HG281D
TCON measurements follow
[code]
VCC 3.32V
VDDR 3.30
VDDA 4.59V
VGL 0.46V
VGH 0.59V
VGH_M 0.18V
F400 4.85V
VDD+1.8V 1.80V
TCONDRY 2.97
OE 0.61
DEO 0
SDA 3.3
SDL 3.3
V1 4.49
V2 4.37
V3 3.62
V4 3.33
V5 3.14
V6 2.85
V7 2.50
V8 2.41
V9 1.89
V10 1.52
V11 1.33
V12 1.00
V13 0.22
V14 0.07
4.83V on each side of L200
[/code]...Leave a comment:
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Re: Another HannsG HG281D
Yes, 4.85V at F400
Bingo!
Well at least we know it's getting the right voltage input now....Leave a comment:
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Re: Another HannsG HG281D
Yep, it's 1.5 Ohms and I just double checked all of the power pins, no continuity with anything else and Q14 source. BTW, this meter reads about 0.8V at continuity so 1.5 isn't that far off....Leave a comment:
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Re: Another HannsG HG281D
I figured out why I was having such a hard time following the +12V to the Q14 source pins:
Q14 source is connected to pin 4 of the power supply header, which is 5.05V and goes through FB14
1.5Ω from Q14 source to power pin 4.
Also I think I had a short between the logic board and a screw terminal the last time I took voltage measurements - I had placed an antistatic bag behind it for insulation but just noticed that it slips around bit. I hope that didn't do any damage. I'm now seeing 4.88V at Q14 source, 4.86V...Last edited by Capt. Cap; 10-10-2018, 06:06 PM.Leave a comment:
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Re: Another HannsG HG281D
Sorry, I should have stated that clearer, by no resistance I meant 0Ω, not open-circuit. Or in this case, 0.8Ω with my HFT special
I bothered mentioning because, just like you said, they checked out bad at first due to a layer of crust over the solder. They're really finicky to check, the only reliable place to probe seems to be the very skinny top metal edge of the bead. I hate drilling the probe tips into the solder, makes me feel like I'm going to break these tiny SMD components, but it seems like the only...Leave a comment:
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Re: Another HannsG HG281D
Logic board PM549DA3 M06 VER6.0 images attached
Q14 is a [URL="http://www.farnell.com/datasheets/1704686.pdf"]9435GM P-channel enhancement-mode power MOSFET[/URL]
Q15 is a [URL="https://www.diodes.com/assets/Datasheets/ds30896.pdf"]2N70002K N-channel enhancement mode MOSFET[/URL]
Pins 1-3 are source, 4 is gate, 5-8 are drain
I poked around some more with the multimeter while I had the logic board completely detached for the photo session.
For Q14,
LVDS pins marked 1-3...Leave a comment:
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Re: Another HannsG HG281D
No worries, I hope you didn't lose anything
Sounds like my typical week.
I'll check resistances on Q14 tonight, see my reply to budm for voltages.
I have v6.0 of the board, it's mostly the same but seems to have less parts populated, pictures are pending.
The CCFL switches on and off at the appropriate times when the computer starts / stops sending video to the display, so something is getting signalling from somewhere, though I don't know how much logic board is...Leave a comment:
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Re: Another HannsG HG281D
Yes, connected, sending signal over HDMI, made sure it's not asleep, and the CCFL is powered on.
The CCFL does power on / off with connecting and disconnecting HDMI, and when the computer goes to sleep, so there is some sort of signalling still working there.
Yes, also checked all of the power input pins, they're as follows:
1 yellow 12.03
2 orange -0.04
3 red 4.89
4 green 5.05
5 brown -0.04
6 black 3.14
(ground reference is an on-board...Leave a comment:
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Re: Another HannsG HG281D
I started checking resistances and voltages on the TCON, the voltages were all way off (VGL, VGH, and VGH_M are all 0V) and eventually got back to F400 which has 0.84V on both sides.
Not sure what the supply voltage is supposed to be to this TCON, but it seems U404 and U406 are not going to be cranking out VCC and VDD+1.8v respectively from 0.84V.
So back to the logic board, V18S is 1.784V and V33S is 3.30V, but the pin 1 of the TCON LVDS (which carries power to the TCON) was only 816mV (same as was on the TCON at the time, it...Last edited by Capt. Cap; 10-09-2018, 01:26 AM.Leave a comment:
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Re: HANNS G HZ281 White Screen
Doesn't look like any reliable retailers have it available in small order quantities [url]https://octopart.com/search?q=buf07704&start=0[/url]
but you can get a single [URL="https://www.aliexpress.com/item/TLC5921-AAT7203-CM2031-AOTR-TA8223K-ICN1314-W83323G-TA8777AN-TA8777N-TA8777BN-TPS65251-ALC5633-BUF07704/32896677308.html"]BUF07704 chip here[/URL]
Probably not the real thing, but like momaka says, it may work well enough.
Let us know how it goes, I could be in the market for one myself soon ...Leave a comment:
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Re: Another HannsG HG281D
Also, I checked F400, was getting some resistance there (~35 ohms) but I get that just touching the tips of the probes together.
I need to dig up my good multimeter, but in the meantime I think F400 is ok.Last edited by Capt. Cap; 10-07-2018, 07:01 PM.Leave a comment:
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