Re: Asus VH235T-P 2 seconds to black
I only changed out the bulged capacitors. And this monitor has a CCFL backlight, not LEDs.
EDIT: After turning it off and back on again, now it's displaying the 2 seconds to black problem.
bmwracer
Member
Last Activity: 10-21-2021, 09:13 AM
Joined: 03-07-2013
Location: Torrance, CA
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Asus VH235T-P 2 seconds to black
Hi all,
A year or so ago, I got an Asus VH235T-P monitor from my nephew that had no video. After I replaced a couple of capacitors, it seemed fine, but not long after I put it back together, it started to have 2 seconds to black problem. I took the monitor apart and poked around for a while, but gave up.
Today I decided to revisit the monitor and after I powered it up, it's not showing the 2 seconds to black problem (yet). It's been running for an hour now and it's still ok. Why?
Any explanation why it would be working fine (so far) after this long... -
Re: Vizio VO47LFHDTV10A - No Backlight
So far, the TV's been running fine... I've got a heat gun I can use to warm things up....Leave a comment:
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Re: Vizio VO47LFHDTV10A - No Backlight
Thanks for the reminder.
I suppose if I have to get at the lamps/sockets, most/all of the boards will have to be removed and that should eliminate the high voltage threat, right?...Leave a comment:
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Re: Vizio VO47LFHDTV10A - No Backlight
It's been over a year, but I finally got back to this HDTV.
Since my last post I haven't turned on the TV... Until now.
It powers up and I have a picture at the moment, but I suspect over time it'll shut itself down like before, like something heats up or charges up. Then it turns into a 2 seconds to black issue.Leave a comment:
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Re: Vizio VO47LFHDTV10A - No Backlight
Correct.
Could/would the failure of one or both inverters cause this new failure to occur?
How does the protection circuit work? Does it sense overly high current?
If it is a bad ccfl or socket, that means I'll have to open up the TV even more to get to those parts... A bad socket would be repairable... A bad ccfl? Probably not.
...
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Re: Vizio VO47LFHDTV10A - No Backlight
Checked the resistance of the windings for all four transformers (two per inverter board)... They're all the same.
I turned the TV on several times and noticed that on two occasions, it appeared that one of the ccfl tubes in the center of the screen was off, but I couldn't replicate it after those two times... Maybe a ccfl tube on the verge of failing?...Leave a comment:
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Re: Vizio VO47LFHDTV10A - No Backlight
Would the fact that I see an image, albeit for a couple of seconds, confirm that those parts are OK?
EDIT: On second thought, maybe that a false conclusion...?
A good idea, I'll check the winding resistance of the Master and Slave inverter boards... Thanks!...Leave a comment:
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Re: Vizio VO47LFHDTV10A - No Backlight
Is there a way to determine if the transformer is bad?
If it is the transformer, this could be a deal breaker since trying to find a sole sourced/proprietary replacement transformer will be nearly impossible....
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Re: Vizio VO47LFHDTV10A - No Backlight
Would a single failed tube cause the entire screen to go black?
I would've thought a single failed tube would show up as a black streak across the screen....Leave a comment:
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Re: Vizio VO47LFHDTV10A - No Backlight
Well, that didn't last a week... Different problem:
Now I get a display, but it only lasts for a couple of seconds and the screen goes blank... I can repeat this every time I turn on the TV.
I'll have to do some poking around, but I suspect it's the power supply... The Asus computer monitor that I was planning to work on has the same issue.
Groan.
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Re: Vizio VO47LFHDTV10A - No Backlight
This is the eBay seller: [url]https://www.ebay.com/usr/giorgio11185[/url]Re: Vizio VO47LFHDTV10A - No Backlig...gio11185[/url]...Leave a comment:
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Re: Vizio VO47LFHDTV10A - No Backlight
I've done more than my share of removing and installing electronic components at work, so it's second nature to me... Having the right tools available helps a lot.
...
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Re: Vizio VO47LFHDTV10A - No Backlight
Slight hiccup:
I was using the TV on a regular basis to burn it in and the backlight went out again.
This time, the Master inverter board failed: it showed a short between Vin (24V) and GND. I removed the IC and MOSFETs and replaced them with the ones from ShopJimmy and now everything is good again.
Again, I'd have to speculate that the previous IC and MOSFETs that I bought and installed from eBay were of questionable quality... Let's hope the parts I bought from ShopJimmy are much more ro...Leave a comment:
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Re: Vizio VO47LFHDTV10A - No Backlight
Thanks! And thanks for your support!
Now I've got to figure out what's wrong with my nephew's 24" LCD computer monitor.....
...
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Re: Vizio VO47LFHDTV10A - No Backlight
Success!
I made one final replacement of the IC and MOSFETs on the Slave inverter board using a parts kit from ShopJimmy.com and it seems to have fixed the problem...
The only thing I can speculate is that the other ICs and MOSFETs that I purchased from eBay were bad/defective... I'm going break-in/burn-in the TV just to make sure that this repair isn't temporary......Leave a comment:
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Re: Vizio VO47LFHDTV10A - No Backlight
Well, it seems pretty obvious that there's something wrong with the Slave inverter board, but I can't figure out what... I've replaced the IC and the MOSFETs (multiple times) and the board still shorts out not long after power up.
Could it be one or both of the transformers? They don't show a short condition on my DMM.
Could it be the support circuitry (surface mount diodes, transistors, caps, resistors)?
I'm nearly resigned to the point that I'll have to buy a replacement Slave inverter board......Leave a comment:
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Re: Vizio VO47LFHDTV10A - No Backlight
Today:
1. I removed all eight MOSFETs from the Slave inverter board, reconnected the power cable and the flat cable from the Master inverter, but did NOT connect the two-wire connector to the CCFLs.
2. Turned on power and about 3/4 of the blacklight turned on (see photo) and there was no high pitched whine from the transformers on the Master inverter board as from the previous tests.
3. I would've thought the Slave inverter would power half of the backlight, but this is clearly not the case... Why? What is the main...Last edited by bmwracer; 02-15-2018, 10:35 PM.Leave a comment:
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Re: Vizio VO47LFHDTV10A - No Backlight
Well, that was short-lived: The backlight died again and the Slave inverter board shows another short (Vin to GND) condition again... Groan.
I suppose it's just a repeat of the previous failure, but it just took a little longer for the Slave to fail this time.
I completely understand... I really appreciate all the help and information you've given me so far... Thanks!
The fuses on each inverter board still show to be good... 0 ohms....Leave a comment:
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Re: Vizio VO47LFHDTV10A - No Backlight
Correction:
It wasn't half of the backlight... I didn't have the room dark enough.
This is what the display looks like now... But I still get that high pitched whine from one of the the Master inverter's transformers....Leave a comment:
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