Re: Vizio E420i-AO tech help?
If I recall correctly,there were 5 rows of 10 LEDs. Each row consisted of two half strips (L1R1, L2R2, then repeated. The other interesting fact is that you could not test the R1 or R2 half strips alone. THey had to be plugged together with their counterpart L1 or L2 halves in order to light up. Then BOTH halves would light up from the tester when injecting voltage at the R1 or R2 test points. Only the L1&2 halves would light up from the tester by themselves. At first I thought I got bad strips but once I recognized the pattern, I...
HGSR
Member
Last Activity: 04-08-2017, 06:41 AM
Joined: 03-16-2017
Location: Round Hill VA
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Last edited by HGSR; 04-07-2017, 12:00 PM. -
Re: Vizio E420i-AO tech help?
E420i-AO Reply cont. 2
To some newbies like myself, you may note these LED testers state you can test the LEDs "without disassembling" the unit. This is only true if you know what you should be seeing in voltage draws. Before replacing any LED strips, I applied the tester to the + and - pins of L1 and L2 at the cable connector (disconnected from the board of course. The tester showed a 45v draw by the L1 array, and 90v draw by the L2 array. After replacing all the LED strips with "new" set procured of eBay, and re-assembling...Last edited by HGSR; 04-07-2017, 08:32 AM.Leave a comment:
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Re: Vizio E420i-AO tech help?
Reply cont.
In the previous posts, you will note I had only measured L1+ and L2+ as shown in all videos on this subject. The voltage I found was 67v on both. I assumed something or some setting was clamping the voltage output to 67v vs the 90 and 100 required. Others have posted finding the LED driver voltage at 66v on this model but did not post why or what a resolution to the problem was. Here it is: (this is old news to knowledgeable techs but news to some of us)
As Bud stated, the LED driver section of the PS was in PROTECTION...Last edited by HGSR; 04-07-2017, 08:35 AM.Leave a comment:
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Re: Vizio E420i-AO tech help?
E420i-AO FIXED!!! Thanks to BUDM even an old dog like me can learn new things. Bud, I owe you an adult beverage if we ever meet!!
I'm posting what I found and did on this "No Backlight but Sound" problem so the next guy that does search on this model can benefit.
Note: As a veteran of other boards on other subjects, I may use more than one reply to post this info. I've ever been bounced in the middle af a lengthy response and had to start all over writing it. So multiple short posts are better.
For those...Leave a comment:
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Re: Vizio E420i-AO tech help?
Thanks for the quick response Bud. Wow, maybe I haven't lost it completely :-). That's what I was thinking too. I'm going to wait till I receive the LED tester before I crack this thing open. I'm also going to order a set of LED strips for this unit from ShopJimmy. As long as I'm in there I may as well replace them. This unit has a lot of hours on it. Small investment.
Vince, Thanks. I've been watching them for days. That guy Tampatech has some good vids.
Thanks Guys, I'll let everyone know what happens when I open this up...Leave a comment:
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Re: Vizio E420i-AO tech help?
Also, I forgot to state there was no video signal input to the tv. If that matters, let me know. I'll redo with a cable from the cable box connected and a tv station playing.
Sure is looking like an open load on L1. Guess we'll find out when I open the screens up to get to the LEDs. Am I thinking right?Leave a comment:
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Re: Vizio E420i-AO tech help?
Bud,
Here's. My readings following your directions exactly I believe:
- AC cord remained connected throughout the testing
- LED cable remained connected to the board throughout all tests
- BLACK meter lead was connected to the metal chassis
Pin
L1- set power-off .39v (went to zero if I touched the metal chassis with my hand)
set powered on .008v no initial spike I could detect
L2- Set powered off. .39v (went to zero if I touched metal chassis with my hand)
Set powered on. 54v initial...Leave a comment:
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Re: Vizio E420i-AO tech help?
Oh. I see my error. You said L1- and L2-
I'll check that tomorrow. I did that check once before. I seem to recall the voltage floated on those pins but I'll verify and report back.
Re: wrong data.
You are correct. I Apologize.
/hLeave a comment:
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Re: Vizio E420i-AO tech help?
Oh ok. 67.1 on both 1&2.
Doesn't matter if the connector is connected or not. Voltage readings are the same on Vout1+ and Vout2+
The ramp to 128v and decrease to 67.1.
According vto the ShopJimmy video in this model, one side drives 3 strips and one drives 2 strips. The active, normal voltages should be 100v and 80v if all is well.
On the 4 boards I have installed and measured all have read 66.7-8v or 67.1 at stasis.
/herbLast edited by HGSR; 03-31-2017, 02:44 PM.Leave a comment:
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Re: Vizio E420i-AO tech help?
Ok. I'll locate L1&2 and report back. Im assuming those are coils.
I don't have a schematic of this BD so I'm guessing a lot.
I'm a little gun shy having already cooked one ps BD.
Don't ever get old.
/herbLast edited by HGSR; 03-31-2017, 12:58 PM.Leave a comment:
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Re: Vizio E420i-AO tech help?
Got it. Excellent! Thanks Bud. Makes perfect sense. I'll bet it's an open since the initial ramp goes to 128v before clamping to 66v. Do you think a short or open on one side of the dual output would cause both sides to go into protection?
Looks like I'll be replacing the LED strips. Want to test them before I pull them though. Just so the next guy that has this problem might have a fighting chance.
Again, Thanks.
/herb...Leave a comment:
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Re: Vizio E420i-AO tech help?
MUTE SCREEN ?!?!?!?
Found this on the VIZO site. This is what is scaring me about my problem. I'm concerned there is some setting somewhere I can't see. If I knew how to "reset" the darn thing it might help. Then, sanity returns and I remember I replaced the logic board. And yes, I tried this and nothing changed. But it is exactly how this set is functioning.
FROM VIZIO web site:
If there is no video but you have audio or you have intermittent video:
Press and hold the mute button on the...Leave a comment:
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Re: Vizio E420i-AO tech help?
Your point is well taken. That $49 kit from ShopJimmy.com will replace all 5 LED strips with all new ones. So $49 is the total cost if I order from SJ. I'm still going to wait for that LED tester to arrive before I open the screen or order new strips. I want to know if the strips are bad and causing this 66v LED driver voltage problem. No one else has solved it yet and it's not uncommon. Maybe someone else can benefit from this effort.
I'm finding that you can beat the prices of ShopJimmy on eBay but for convenience and customer service,...Leave a comment:
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Re: Vizio E420i-AO tech help?
Good input. Thanks Bud and Dick. Have done the panel removal research and there are videos on doing that to this model. I'm comfortable doing it. I'm an OLD electronics tech from the discrete component days. The first computer I worked on had tubes in it, as did the last TV I worked on ;-) In those days we detested doing "board swaps" to fix a problem rather than trouble shooting it. We found the bad component and repaired the board, replacing the bad tube, capacitor, transistor, diode or chip (they were new technology back then). So this...Last edited by HGSR; 03-31-2017, 07:31 AM.Leave a comment:
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Re: Vizio E420i-AO tech help?
AHA! Thanks Dick. Could you give me a hint what to do a search on or how trouble shoot to verify the problem. Is there a way to use a meter at the cable connector end? Otherwise I'm assuming I'll need to open the screeens to get to the LEDs and driver strips. I don't have a 24v DC power supply so I thought maybe I could Isolate each half of a strip (by unplugging them from the boards and each other, and use a 12v battery to test them. Not sure how to check the driver/distribution strips that are fed by the LED cable of the PS bd. Does this sound reasonable?...Last edited by HGSR; 03-30-2017, 05:39 PM.Leave a comment:
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Re: Vizio E420i-AO tech help?
OK Folks, we're back in problem mode again. I replaced the PS BD that I fried with a probe slip, and this board measures EXACTLY the same as the other 3 did. There is no backlighting. I have sound, a picture (seen with a flashlight) and all other functions that I can tell with no backlight. I have replaced the LOGIC board and the symptom does not change. When the unit powers on, the voltage on Vout1 and Vout2 of the LED connector goes to 128v and decreases to 67.1v and holds there - with the LED cable connected or not. In fact, with...Leave a comment:
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Re: Vizio E420i-AO tech help?
Just so everyone that is generous enough to help me knows, I've put a $100 budget on this repair. So far I've not spent $25, and that's been on postage to return 2 PS bds ShopJimmy.
My time is not of value as I am retired and needed a project ;-) I was an ET many years ago and I'm enjoying this effort. I am frustrated with no schematic or o'scope like the old days. But you guys are showing me it's possible to actually do this without them.
I've just ordered another PS BD since I"m pretty sure I've blown something else this one...Leave a comment:
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Re: Vizio E420i-AO tech help?
Dick,
Got a snag (see post above). Will return to this string when I get another PS BD. Then I'll let you know where we are with the 66v issue. It's definitely NOT the logic board (changed it) unless I have another bad one.
There have been 3 PS bds in the machine all with 66v on the LED driver cable pins with the LED cable disconnected or connected. Go figure.
/herbLeave a comment:
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Re: Vizio E420i-AO tech help?
Bud,
Yes, that's exactly what they did on all three PS boards, the original plus 2 from shopJimmy. So suspected it wasn't caused by the PS boards. I just put another logic board in and got the same result - sound, picture but no backlight. Outputs on +Vout1 and +Vout2 settled after initial power-up to 66v.
But now I've screwed myself. As I was checking and comparing voltages on the PS board must have pissed something off and got a loud crack and everything silent. Checking voltages on the ins of the logic cable to the...Last edited by HGSR; 03-26-2017, 11:42 AM.Leave a comment:
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Re: Vizio E420i-AO tech help?
3.2v...Leave a comment:
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