e420vse no standby light

[budm]

Re: e420vse no standby light

That is multi-turn (10-turn pot) trimpot for fine adjustment, it is either for the output voltage fine adjustment or the constant current output adjustment, I am surprised the kit did not come with the instruction.

[geobaja]

Re: e420vse no standby light

Budm. Thank's I did check the site for the parts kit but it said : "Sorry but this item is currently unavailable. "

[budm]

Re: e420vse no standby light

It shows the components that need to be replaced, so if you can buy all those parts yourself then you can try to fix the board.

[geobaja]

Re: e420vse no standby light

Budm the " HAI 7207PC " is very hard to find, looking all over for it, no luck

[geobaja]

Re: e420vse no standby light

Easy fix for Vizio e420vse that works for a couple of minutes and then the Image goes out (black screen), I'd tried to do the mod we discuss before without any luck, but in the process noticed that chip HAI 7201PC get's to hot causing an internal short. so I added a 12vdc Fan I had , and that fixed the problem, +vcc pin 3 red and -vcc pin 8 purple. its been working for a week so far

[budm]

Re: e420vse no standby light

One way of solving it. You may try using old heat sink from MB also. Good to see you get it running.

[geobaja]

Re: e420vse no standby light

I did tried a heat sink, but after a while it get hot and shot the display, I'd notice the ebay guy is selling the power inverter kit again ($40) if someone got the kit from him maybe will like to share the instructions, I did the wiring as the picts. but didn't work for me (got the $16 inverter from china)

[ecking767]

Re: e420vse no standby light

Budm the " HAI 7207PC " is very hard to find, looking all over for it, no luck

I was doing repair on an Emerson LED TV LE220EM3 and there was a HAI 7209PC chip on board for the LED lighting circuit. I was hoping that this HAI 7209PC was an replacement for HAI 7207PC but it not. The HAI 7207PC is defective straight out the factory.Pin 6 and 7 will short out in time and then your fuse will blow. Your Idea is good (the heat sink or fan) for HAI 7207PC chips that are still functional (MAYBE).The inverter is the only solution for now

[diller-33]

Re: e420vse no standby light

Hi all. Well I have been trying to fix my Vizio E420VSE for a few weeks now. So far I have separately replaced the main board, the power supply board and most recently the LED driver board. I have the same symptoms, no indicator light, logo on screen for about 3 sec screen lights for about 6-8 seconds then all goes black. Ive reinstalled all the original boards and checked the chip 7207PC and it gets real hot. Today with the replacement driver board, I get nothing. No light up and no heat. I think the replacement driver board is defective. I am not too surprised as to how scarce they are now.
I returned the first two boards already.
I am thinking of trying the fix as in post # 47. I guess I will have to use the ebay parts as described in post 18 and 20 . ( 100 W boost set up converter)
Should I start a new thread on this? I have a few dumb questions, are the LEDs somehow defective? Why don.t I ever see 25 volts on the pins on the power board? Thanks in advance.

[diller-33]

Re: e420vse no standby light

just looked at the pic and did that
unscrew the heat sinks and the fets bend right over and
then reinstall the heatsinks and remove the two caps lay the one down and put the other one in with 24v and ground

Hi, I ordered the 100W boost step up convertor but the pictures you mention above are no longer large enough to see. I am not real clear what points to connect, jump etc. when the board comes in a couple weeks. Can anyone please assist with a few details for the connections? There is pictures in geobaja post on 7/30/2013 but he also says the fix didn't work??? I can send a picture of the board and try to show the pin label.

The ebay seller that sold the $50 repair kit (unavailable now) explains as follows:
(repair your vizio 42 e420vse with a bad led power board. you will need to solder 3 wires and add 2 jumpers to add the new power supply onto the old bad unit. all parts are in the kit, and you will need a soldering iron . questions? )

Thanks in advance.

[skyanchor]

Re: e420vse no standby light

I haven't checked back here for a while. I do have the original picture somewhere, but I figured it would be quick and easy to solder onto the bottom of the board where the test points are marked (+24V, GND, VLED). Furthermore, since it's my own TV and I didn't feel like reconfiguring the heat sink and large capacitor, I left the eBay converter board as is. I merely cut out a couple of slits in the back of the TV, using a knife to cut the plastic vertically along the air vent holes, such that the case bends around the large capacitor. I think if you put that capacitor sideways across the output, you don't need to unsolder the heat sinks from the board or cut the case. The trick is to affix the board far enough down so that it's vertically near the center (and directly beneath the air vent holes), and so the plastic case will easily bend around it, such that there's really no noticeable bulge. I used double-sided foam sticky tape to affix the board to the chassis.

So when I first plugged the TV in after installing the converter board, I heard a high pitched squeal from the power supply and the LEDs were very bright...voltage was 90 some volts!..I panicked and unplugged the TV. Turned the voltage pot way down...tried again...same thing. Voltage would not go down below 86 volts no matter how many turns I made on the potentiometer. Then, something failed on the Vizio driver board, I think, as the high-pitched squeal suddenly went away. It was like the two power supplies had been competing with each other for a time.

The original failure mode of the TV as I remember was that it did work for a few moments when it was first turned on, then the screen went dark. The takeaway from this anecdote is that the original board wasn't completely dead and also didn't appear to be completely disabled as the jumpers (top diagram) were supposed to accomplish. Anyway, I was subsequently able to adjust the voltage way down to below 60 volts (very dim backlight), then back up to 80 volts, where I left it. That seemed to be a pretty decent brightness. I wanted to go a little lower than full brightness as this isn't a constant current supply, which is what you should have when driving LEDs.

As luck would have it, I see there is now a constant voltage/constant current 80V boost converter for sale on eBay, for just $5 more than the original $14 eBay converter (which, I noticed, is now available from some sellers for less than $10).

http://www.ebay.com/itm/DC-600W-10-6...-/131190113105

The way that works, as I understand, is that there are two pots (pictured), one for voltage and one for current. Since only one mode works at a time (constant current or constant voltage), there is automatic switchover from one mode to the other, based on which mode is the most restrictive. So, if I set a maximum voltage of 80V, no current setting can make the voltage go higher than that. Likewise, if I set a maximum current of 0.60A, no voltage setting can make the current go higher than that. I was thinking that when I install one of these boards, I will set the voltage a little higher, maybe 83V if it will go that high, and then set the current adjustment till it brings that voltage down just a hair. Thus, the current limiting has taken priority and should keep priority, which is what you want for protection of the LEDs.

[skyanchor]

Re: e420vse no standby light

Thus, the current limiting has taken priority and should keep priority, which is what you want for protection of the LEDs.

I should clarify my previous post, as I think I gave out misinformation. I was assuming a single series string of LEDs comprise the backlight, but I believe there may be two independent series strings, which are shorted to series/parallel operation when the original mod is performed. It's very important that each series string have its own independent constant current source. Otherwise, if there were two series strings connected in parallel across the same constant-current supply, and one string went open, I think you can see from basic electronics that the voltage would double to try and force the lost branch current through the remaining good series branch (doubling that current through each LED in the branch). That would be a bad thing!

So when I said that constant current is what you want for protection of LEDs, that only applies to an individual series string of LEDs. That's why these original manufacturer's TV driver boards appear to be more complicated than you or I might otherwise have expected: there are 2 (or more) independent (yet tracking for brightness control) constant current sources on the board!

Please jump in with any further questions/corrections/clarifications. In the meantime, till we get this all figured out, I'd advise sticking with the original 60-97 volt boost converter offered on eBay, now priced at only $7.83 with free shipping:

http://www.ebay.com/itm/DC-DC-Boost-...-/141316789506