Folks,
I admit it -- I'm just stubborn. I've been working on repairing a "free" 42" Vizio my neighbor gave me for months. You can read back through the first 3 acts, starting with the last: [url]https://www.badcaps.net/forum/showthread.php?t=22606[/url]
I'm now on my second replacement T-Con board (part #: 6870C-4200C, picture below) from ShopJimmy (which definitely works better than a used pull I got off eBay). I now get a picture, but it has two issues:[LIST][*]A big one: the rightmost quarter of the picture is chopped off and replaced by a copy of the third...
mikew67
Member
Last Activity: 10-31-2016, 10:35 PM
Joined: 08-03-2012
Location: Palo Alto, CA
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Vizio VO42L saga, Act 4: Got a picture, but it "stutters"!
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Re: Bad T-Con replacement board?
Please see the followup to this thread in my new thread at:
[url]https://www.badcaps.net/forum/showthread.php?t=22606[/url]
(Might as well consider this one closed.)
MikeRe: Bad T-Con replacement board?<br ... <br /> MikeRe: Bad T-Con replacement board?
Please see the followup to this thread in -
Vizio VO42L saga, Act 3: Signal tracing a T-Con board
Folks,
Previous acts were reported in the following threads:[LIST][*][B]Vizio VO42L, Backlite & PS OK, no pic, now what?[/B] [URL="https://www.badcaps.net/forum/showthread.php?p=259787#post259787"]https://www.badcaps.net/forum/showthread.php?p=259787#post259787[/URL] -- which led to tracing a bad supply voltage down to inside the T-Con board.[*][B]Bad T-Con replacement board?[/B]
[URL="https://www.badcaps.net/forum/showthread.php?t=22413"]https://www.badcaps.net/forum/showthread.php?t=22413[/URL] -- After the T-Con board was replaced and all voltages were... -
Re: Bad T-Con replacement board?
Tom, see the voltages in #9 msg in this thread. I presume those measurements are what you're referring to.
MikeLeave a comment:
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Re: Bad T-Con replacement board?
OK, did another diagnostic. Remember that Tom66 said that VGL should be around -10v, when it's actually around -3.5v. Budm suggested that a (downstream, on the flex cable) row/column driver IC might be bad.
So I measured VGL and VGH again, with both panel flex cables connected (as before), with first one, then the other disconnected, and finally with both disconnected. Here are the results:[LIST]VGH stayed at approx. 25v in all cases.[/LIST][LIST]With both flex cables connected, VGL = -3.5v, as noted before.[/LIST][LIST]With left flex disconnected,...Leave a comment:
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Re: Bad T-Con replacement board?
Thanks, budm. If that's the case, am I "dead in the water", i.e., beyond a practical repair?
Mike...Leave a comment:
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Re: Bad T-Con replacement board?
And, where can I find tech info on T-Con boards in general, and this Philips board in particular?
TIA,
MikeLeave a comment:
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Re: Bad T-Con replacement board?
Thanks, tom66 and budm, for the advice.
So if I disconnect the 2 LCD panel ribbon cables and power-up, will that harm anything? If I then check VGL without a load and it's now ~-10v, does that then point to a bad panel? (Sigh....)
BTW, is VGL a bias voltage, i.e., very low current requirement?
Thanks, as always,
MikeLeave a comment:
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Re: Bad T-Con replacement board?
Measured T-Con voltages:
[CODE]
V(F1) 11.88v
VCC 3.347V
VCC1.8 1.840V
VGL -3.527V
VGH 25.07V
[/CODE]
Are these OK?
MikeRe: Bad T-Con replacement board?Code:Re: Bad T-Con replacement board? Measured T-Con voltages: [CODE] V(F1) 11.88v VCC 3.347V VCC1.8 1.840V VGL -3.527V VGH 25.07V [/CODE] Are these OK? Mike
Measured T-Con voltages:
[CODE]Leave a comment:
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Re: Bad T-Con replacement board?
Any idea where the panel ID sticker is? (Might be under the sheet metal that the power board and main video board are mounted to. Shining a flashlight in the 1/4" gap between that and the panel sheet metal back, I "think" I see a sticker. If so there are about a dozen screws to remove to check
MikeLeave a comment:
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Re: Bad T-Con replacement board?
Sorry, typo (corrected later). The supply voltage is 11.94v.
Figured out how to actuate the connector latches. Removed it and examined both plug and socket. All OK (a couple plug pins aren't populated). Re-inserted. Same result. Plain white screen with black lines.
MikeLeave a comment:
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Re: Bad T-Con replacement board?
BTW, the bottom connector with "squeeze release" buttons on the bottom is problematic. The plastic buttons popped off in one or another of my attempts to remove the plug and reinsert. Is it easy to mangle the pins on this plug or socket? (I know enough to be gentle and careful about alignment when inserting the plug :-)
Now that the plastic buttons are missing, how can I release the plug? Insert a small flat-blade screwdriver from above to release the metal-hook catches?
MikeLeave a comment:
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Re: Bad T-Con replacement board?
OK, here are pics of the original T-Con PCB and the replacement. No barcodes seen anywhere on them, but the second line of "rubber-stamped" text on the white block is the same, "4200C1" (as is the PCB silkscreen labeling), but not the first line. Is that significant?
WRT voltages, the replacement measures:[INDENT]At the F1 fuse input: 11.94v
At the VCC test point: 3.35v
At the VCC1.8 test point: 1.84v[/INDENT]
What now?
Mike
PS: Note the browning around the VCC supply on...Leave a comment:
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Bad T-Con replacement board?
Folks,
See my earlier thread: [INDENT][url]https://www.badcaps.net/forum/showthread.php?p=259787#post259787[/url][/INDENT]
on chasing down a no-video problem with my Vizio 42" LCD. Chased the problem down to some component on the T-Con board that was dragging down the internal 3.3v LDO output (from 12v input to the board). Started removing discretes without finding the problem. Looks like it might be a blown main IC (Philips TL2412MC). At this point I ordered a replacement T-Con board: [INDENT]Desc: LC420WUN-SAA1 CONTROL PCB 2L
P/N: 6870C-4200C
[/INDENT]
... -
Re: Vizio VO42L, Backlite & PS OK, no pic, now what?
Aha, one more metal shield to remove. Here's a pic of the T-Con PCB.
Good suggestion. I think we're on the trail of the problem here. The fuse was OK, and the voltage on it (both sides of course) is 12.0v with power on.
But the voltages around U31, the only LDO I could see on the board (just under the rubber stamped numbers) aren't right. The output, pin 2 & tab, is connected to a PCB trace labeled "VCC1.8", but the voltage on it is only 0.569v. (I'm presuming this regulator is supposed...Leave a comment:
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Re: Vizio VO42L, Backlite & PS OK, no pic, now what?
T-CON board?
I checked a couple fuses on the main board already (all that I could find -- fairly easy to recognize, white with metal ends. All OK.
Yes, the delta between the adjustment leg and the output is 1.25v on all the LDO's I could find.
MikeLeave a comment:
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Vizio VO42L, Backlite & PS OK, no pic, now what?
Folks,
Thanks for this useful forum. Previous threads have allowed me to get this far, but now I'm stuck.
Summary:
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Vizio model: VO42L FHDTV10A
"Vizio" logo is orange with power off, goes white with power on.
Flourescent backlight comes on, too.
But no video appears, screen is blank/dark, even when pushing Menu and Input buttons on TV.
TV failed suddenly, as if power failed.
Power supply board voltages appear(?) to be OK.
LDO chip output voltages on main PCB appear(?) to be OK.
No apparent bulged caps.... -
Re: New Members - please post your introductions here
Hi, Mike here, from Palo Alto, CA. (Hey, right in the heart of Silicon Valley :-) Mainly do software, but have been doing a lot of hardware lately, mainly embedded systems, in the form of wearable sensors for medical and fitness applications, with LPRF (Low Power RF). See my volunteer group on Facebook, Maker Corps, where we try to figure out how to apply these devices (and any other assistive technology) to solutions for folks with disabilities.
You can find a picture of one of my wearable gadgets in that FB...Leave a comment:
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