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ive got a 65" mitsu that fails to power on, i get a lit led for a few secs, some clicking from somewhere on one of the pcb's and power down, the self diag reads 2-2. ive looked all over the boards and dont see any bulging caps, i know the error 22 is usually a bad pico from the convergence ICs but i dont want to yank the boards out and start soldering without being sure its them. if the IC's are bad will i definitely have bad pico fuses? and whats the best way to test the picos?also, im a little concerned about discharging the high voltage from the flyback, should that discharge by itself being unplugged overnight, or do i need to ground it somehow to make it safe?

thanks in advance!

greg in p'cola
 

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Most 2-2 errors in these are due to open pico fuses due to a short in a convergence IC. Sometimes high ESR caps in the convergence supply will cause problems, but the chips are almost always the problem. Several of the low voltage dc supplies going down can cause this error. I would start by checking the pico fuses. The one that is open, if any, tells you what circuit needs repair.
 

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hey tg,

thanks for the reply. would you believe this giant giant tv is still sitting in my dining room not working heh.. took your advice, read your sticky. checked all the fuses, turned out i did have a blown 3A pico. changed the fuse and of course it just blew again, so i got a set of ic's cheap off the bay and swapped them out as well as another new pico.. before i tried to power on i checked for error codes and got a 1-2 for "no error occurred" so i got real excited and turned the power on... led came on for a sec, then off after about 4 secs just like before, unplugged and rechecked continuity on the pico.. blown :\ took the board back out and checked about a hundred resistors, most were really close to specs except for a few that im pretty sure were just in parallel, and one of the bigger 3w 150 ohm metal ones that read wide open on the board, but when i removed it and tested it off, it was right on, 150 ohm.. checked between the 2 holes it came from and its dead shorted.. does this seem to indicate anything, or is that normal? also a few of the small resistors, the pcb directly under the component looks darkened, but the values are right on.. per your sticky, i should just go ahead and replace them i guess?


thanks again for the help, and i know im not doing this all the way you recommend, but understand, the reason this tv has been sitting for a year, i picked up a 50" panasonic plasma for $300 last year from sears, im not interested in putting any more money than i have to into this, its more of project and a learning experience for me than anything.. well that, and the fact that i paid like 2500 for this thing when i got it lol.. im about to head home, if i get time before bed ill post some pics of the pcb..

thanks!
greg
 

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I cannot answer your question without a service manual and the location of the resistor, but if it is as you say, my guess is something else in the circuit shorted or you are measuring a yoke winding.

Check for bad solder connections. Also, where did you buy the ICs? The most common failures are due to bad chips or installation errors.
 

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service manual is here:

https://drive.google.com/file/d/0B6PnEVhEDJ6mOThBejVKY2ltWjg/edit?usp=sharing

resistor in question is R5A46. its location on the pcb is circled in blue. its a bad picture, but you can see the discoloration around the resistors towards the center. the pico is the little glass one F9B01

to answer your question, i got them exactly where you said not to :eek:opssign:
paid $10 for the pair on ebay.. is there any way to test them?


:thankyou:
 

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Re: Fuse F9B01

Hello,

I've got the 55" version of this regedit024's set (WS-55315) and it has the same chassis. My symptoms are pretty much the same. I found the set powering on for about two to four seconds and then switching right off. The error code is 22. I had noticed in the last few weeks some very faint horizontal lines showing up in the picture but was secretly hoping it eventually would be an excuse to replace this set. Well, the better-half put the kibosh on that plan and here I am in repair mode.

An Internet search indicated it was most likely the convergence IC's having caused a short which then caused a fuse to blow with the possibility of destroying some 3.9 ohm resistors at the same time. Well! I checked all the resistors, they look good and measure out OK, solder connections are good as well. The two 5A fuses associated with the ICs checked OK but just to be safe, I replaced the ICs with Sanyo anyway (after all I had seen "something" in the picture). Triple checked all my work, powered it up and got the same symptoms as before.

I then did what I should have done before which was check all the other pico-fuses (there aren't that many). F9B01 is wide open and another Internet search led me to this thread.

I do have the service manual but other than a description of F9B01, I can't seem to find just where in the circuitry it lives or what parts it protects. I checked regedit024's resistor R5A46 and found it to be a nice 150 ohms with a leg lifted however when soldered in place the measurement is zero ohms with either polarity of the multi-meter. I'm not sure this is really a problem without a schematic.

I see this thread kind of died off back in November. Here's hoping there's been a development. At least maybe someone can point me to a schematic?

Thanks in advance!
Scott
 

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F9B01 fuse update

I found a schematic for the V24 chassis. Sure wish it was text searchable! What a pain looking for specific parts. Oh well...

Found the fuse on the main board. +24V runs through it and protects two circuits. One is a DC to DC converter which produces +5V and the other is something on the AVIO board. There are a couple of electrolytics which could short to ground. Visual inspection doesn't show anything. Right now since I've only got the multi-meter I'm measuring about 500 ohms to ground so I can't really simulate what happens to the caps when they've got the full +24. There are a couple of ICs involved as well.

Still, if anyone has some experience with this failure it would save a lot of troubleshooting!
 

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Typically the chip fails and blows the fuse on one of the supplies. If you replaced a chip and not the fuse there is a good chance the new chip failed because of the unbalanced supplies.

Searching schematics and boards for parts gets easier with experience. No easy way around it unless someone has lots of recent experience on these an recalls. I have not worked on them in years and do not recall the layout.
 

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Well, thanks for the information. Yep, it's taking a while to knock the rust off my brain.

This morning I located, purchased ($15.79 for 5 - ouch) and installed the correct 3A pico-fuse with the same result of power off. I sure hope it didn't kill the new chips. Now I've got to pull the chassis again and see if any other fuses blew.

Looking at the schematic, I don't see the power supplied here going to the convergence circuitry but there could be a sneaky way it's done. Fingers crossed.

I also found a thread on one of the "ask" websites which documented a conversation with an "expert tv repair person" that dug through the 24V to 5V circuitry (their set was blowing the same fuse). Unfortunately it too trailed off with no resolution documented.

http://www.justanswer.com/tv-repair/7nmm1-tv-won-t-on-24-6-volt-power-supply-board.html

Still head scratching...
 

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Maybe ... Bad voltage regulator

Pulled the chassis out (again) and starting checking. No fuses were blown this time, mabe because I only cycled the power on the set once.

Looking downstream of the previously blown fuse there's a voltage regulator circuit. First observation was the resistance was only 1.9 ohms (uh-oh, that means over 12 amps at 24v - no wonder the fuse has been blowing) even after letting all the caps charge up. First suspect was an electrolytic cap which checked out good when I pulled it out. Resistance was still 1.9 ohms so I pulled the regulator IC and voila, circuit resistance was on the order of 25k ohms and the resistance between Vin and ground on the chip was only 2.1 ohms. I believe this chip is my culprit!

Got one on order as our local supply doesn't stock one. It's a holiday weekend so hopefully by middle of next week we'll be back in business. Will keep y'all posted.
 

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Solved!

Yes, it was the voltage regulator. Before I soldered in the new chip I was curious and measured the resistive load on the chip's output. About 2.5 ohms. Pretty low I thought. Did some more testing and found no caps downstream to be bad. Looked up the spec on this regulator. With an infinite heat-sink it handles up to 30W and can source 3A. So, I suppose even with that load, it's working well within spec.

Went ahead and soldered it in, replaced all the connectors and gave it the power on test.

Bummer, turned on and then turned off again. Different code though, 26. Hmm... there's no 26 in the manual. Let's unplug it and just try it again. Plugged it back in, powered on and it powered off again, this time with a code of 24 which is not in the manual either. One more try and voila, everything is working just fine. HURRAY! Just in time for the grandkid's three week visit which starts TOMORROW.

I'm wondering if power has to be cycled a few times before they system figures out it is OK. Regardless, we're done!
 
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