Re: Viewsonic 27" LCD turns off after a while -- longer on VGA, Shorter on HDMI?
MP1484 = 3A, 18V, 340KHz Synchronous Rectified Step-Down Converter
The MP1484 is a monolithic synchronous buck
regulator. The device integrates top and bottom
85mΩ MOSFETS that provide 3A of continuous
load current over a wide operating input voltage
of 4.75V to 18V. Current mode control provides
fast transient response and cycle-by-cycle
current limit.
Ambient Operating Temp .............. –20°C to +85°C ;;...
capthook
Member
Last Activity: 09-07-2021, 09:28 AM
Joined: 11-07-2014
Location: Mesa
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Re: Viewsonic 27" LCD turns off after a while -- longer on VGA, Shorter on HDMI?
Ok, well it looks like my IC 502 is getting red hot too... I replaced the mosfet ; it didn't correct anything. So, I put my meter on the other IC I thought might be a problem but it wasn't getting super hot ; IC 502 was ... I'm starting to think this might be the flaw on these boards now. Unfortunately, I'd have to wait another MONTH for this IC... arghhh.... don't know what I am going to do yet -- I did order the MP1484EN ICs ; so I guess i'm still kind of determined to fix the board and not just...Last edited by capthook; 05-04-2017, 10:57 AM.Leave a comment:
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Re: Viewsonic 27" LCD turns off after a while -- longer on VGA, Shorter on HDMI?
Yeah not bad man... I ordered the parts (the IC, and the Mosfet) from china... willing to wait for it I have plenty of displays ; but if that doesn't work i'll just order the new populated board at that point. I noticed the connector at the top looks different, but I can always swap that ...2x mofets were $1.29, the IC was like $1.49 lol ... see this thread again in a month :-(Last edited by capthook; 04-17-2017, 07:58 PM.Leave a comment:
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Re: Viewsonic 27" LCD turns off after a while -- longer on VGA, Shorter on HDMI?
What a bummer. You can get the whole board apparently for around $22 /shipped from china (see link) I just wanted to solve the problem on the PCB instead of ordering the entire unit ; guess i'm gonna wait on some parts from our chinese friends here...
[url]http://www.yoycart.com/Product/537360577727/[/url]Re: Viewsonic 27" LCD turns off afte...d $22 /shippedLeave a comment:
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Re: Viewsonic 27" LCD turns off after a while -- longer on VGA, Shorter on HDMI?
IC502 looks like: MP1484EN
MP1484EN-LF
Manufacturer:
Monolithic Power Systems (MPS)
Description:
Switching Voltage Regulators 3A, 18V, 340kHz Sync Step-Down DCDC
[url]http://www.mouser.com/ProductDetail/Monolithic-Power-Systems-MPS/MP1484EN-LF/?qs=rC7bBWoQAAmtIYZxUlxUkg%3D%3D[/url]Re: Viewsonic 27" LCD turns off afte.../> MP1484EN-LFLast edited by capthook; 04-13-2017, 11:15 AM.Leave a comment:
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Re: Viewsonic 27" LCD turns off after a while -- longer on VGA, Shorter on HDMI?
A better (large) photo of the PCB is attached ; it looks like perhaps a refurb? as that 330uH has obviously been replaced....Leave a comment:
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Re: Viewsonic 27" LCD turns off after a while -- longer on VGA, Shorter on HDMI?
Ok, so maybe I should do that, test / observe pin voltages on the IC and on the mosfet after coil removal ? The IC gets hot... up to 110-120F I think , but not hot hot hot like the coil was (154F) ..Last edited by capthook; 04-12-2017, 06:23 PM.Leave a comment:
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Re: Viewsonic 27" LCD turns off after a while -- longer on VGA, Shorter on HDMI?
[url]http://www.datasheetspdf.com/PDF/9997GH-HF/774796/1[/url]
9997GH = N Channel Enhancement mode Power Mosfet
Drain Source Voltage = 100v ; 11A
R (Static Drain-Source On-Resistance) = 120m ohm / 200m ohm
Gate Threshold Voltage = 1-3v
TO-252 appears to be different... 60v i thinkRe: Viewsonic 27" LCD turns off afte.../1[/url]<br />Leave a comment:
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Re: Viewsonic 27" LCD turns off after a while -- longer on VGA, Shorter on HDMI?
Also is TO-252 the same as 9997GH mosfet?
seems like the same one is also AP9997GH-HF ; 9997GH ; 9997CH....Leave a comment:
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Re: Viewsonic 27" LCD turns off after a while -- longer on VGA, Shorter on HDMI?
ok, good to know... Do you think the mosfet 9997GH above it could be the problem? or the one to it's right? One to the right of the IC is labeled MT1117 . Should I just remove and replace that guy ? It ran for 2 1/2 hours last night before I finally shut it off and went to bed -- so the larger inductor, whilst a bandaid did stop the display from shutting down. I just dont want to damage anything with the 40uH instead of 33uH in that position. Problem is that I cannot find a schematic for this ...Last edited by capthook; 04-12-2017, 12:46 PM.Leave a comment:
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Re: Viewsonic 27" LCD turns off after a while -- longer on VGA, Shorter on HDMI?
All I could find in my parts bin was a 40uH ; of a higher voltage rating probably (it's bigger) ... and I'm a risk taker, so I swapped the stock inductor in the position that was getting hot obviously... it's been running for an hour now without shutting down. Just a band-aid on the situation, i'm sure -- since the IC INL858RN -- IS getting hot, maybe a short, thus overheating the inductor perhaps? The only diodes I can identify on the PCB are the larger black diodes, I think there's three , maybe...Last edited by capthook; 04-11-2017, 11:34 PM.Leave a comment:
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Re: Viewsonic 27" LCD turns off after a while -- longer on VGA, Shorter on HDMI?
correction ... I think these are 33uH ; thus a "330" inductor...Leave a comment:
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Re: Viewsonic 27" LCD turns off after a while -- longer on VGA, Shorter on HDMI?
Input voltage is 19v, 3.42A ... The inl858rn i believe is an LED inverter controller ic... it however doesn't seem to be heating up ; just the inductor... I noticed a russian and then another chinese supplier for the board, and that specific inductor had been replaced with a different 330uH inductor ..?.. But; logic says 95% of the time the inductor isn't the problem it's somewhere else; like to high of a voltage to the inductor itself. Plus I swapped them and the one that wasn't overheating in...Last edited by capthook; 04-11-2017, 08:21 PM.Leave a comment:
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Re: Viewsonic 27" LCD turns off after a while -- longer on VGA, Shorter on HDMI?
Yeah, it sounds heat related like mine... on HDMI she'll last anywhere from 2 minutes - to under an hour. On the VGA input, much longer - sometimes almost 4, 5 hours or more without a problem. To be sure, I hit the same components with the heat gun to see if they were heating up as much on VGA ... they were, but it took much longer to get the heat numbers I was getting with HDMI hooked up.
The 9997GH mosfet seems to be Ok, staying cool and also supplying a voltage of 3.3v for something...Leave a comment:
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Re: Viewsonic 27" LCD turns off after a while -- longer on VGA, Shorter on HDMI?
Since you changed your video card - I wonder if your problem is related to the refresh rate ; did you change it to 60hz? tried multiple resolutions? ...
Mine does it with ALL devices... PS4 on HDMI, PC / Mac... doesn't seem to make any differece. It's definately hardware related on my end with this screen. The VGA input allows use for (hours) without problems. Use of HDMI inputs (either one doesn't seem to make a difference) heats up that 330uH coil really quick (saw it push 155...Leave a comment:
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Re: Viewsonic 27" LCD turns off after a while -- longer on VGA, Shorter on HDMI?
Ok, I swapped the coils ; and the coil still gets hot in that position . ... maybe the mosfet 9997GH / regulator before the coil? ...
I can watch the coil / inductor in that position using a known good 330uH rise to temps above 140-150F , which is when the monitor shuts off. This was heating up components around it, which threw me off initially.
Please see the attached pic, i've highlighted both parts I am referring to....Last edited by capthook; 04-10-2017, 08:14 PM.Leave a comment:
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Re: Viewsonic 27" LCD turns off after a while -- longer on VGA, Shorter on HDMI?
Ok, I thought it was the IC.. but it could be the 330uH coil (inductor) next to it, lol. I got out the laser temp gun, and one of the coils is going up to 140 F , whilst the other next to it sits at a comfy 80 F... no fluctuation. I'm going to replace that first and see what happens
Last edited by capthook; 04-10-2017, 06:22 PM.Leave a comment:
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Re: Viewsonic 27" LCD turns off after a while -- longer on VGA, Shorter on HDMI?
Ok the overheating chip is INL858RN...labeled IC501 on the pcb. Should i just r&r this guy and see what happens? It's the chip with 24 pins closest to the two 330uH coils on the pcb. Temp rises much faster on HDMI input, as opposed to VGA....Last edited by capthook; 04-10-2017, 05:53 PM.Leave a comment:
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Re: Viewsonic 27" LCD turns off after a while -- longer on VGA, Shorter on HDMI?
I don't think it's one of the SOT223's getting hot... it's a chip, I'll have to open it again and grab the numbers off it ; thanks mate.Leave a comment:
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Re: Viewsonic 27" LCD turns off after a while -- longer on VGA, Shorter on HDMI?
If input / output capacitors to that chip are fluctuating in value.. can that cause overheating as well? ... or is that not as common as just a bad chip?Leave a comment:
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