Mitsubishi WT-46805 turns on, goes bright, then off in addition to convergance issues
I have this WT-46805 RPTV I got for free a year ago because it had convergence issues.
Last year: Had convergence issues no adjustments would work at all. At this time, I disconnected and examined the boards, re-flowed bad looking solder joints, etc. Eventually I noticed that R8E00 and R8E03 were burnt. During this debug process I connected and disconnected all the boards for working on multiple times. No problems except the convergence.
So I bought some STK392-040s to repair it, but never got around to it. The TV has sat in the barn for a year and I'm hooking it all back up again, have't done fix yet and dang-it - I left it in the disconnected state. But now in addition to the convergence issue (no surprise, not yet fixed) - the TV now...
- turns on
- I see blue, after about 5 seconds the CRTs start get bright
- Then it turns off in another second or so
This whole process is very brief.
The error check code I get is 1-2 which indicates no problem.
As I was futzing around with it, I missed re-connecting PV connector on the POWER board. This seems to go to DY-R and DY-B. In any event, when I don't connect this plug, the TV stays on & I get 3 lines - red, green, blue.
So I don't know if I've damaged things worse, missed some connection, or ????. But it was working last time I had it connected a year ago...
> Any idea what might be going on?
One extra piece of info, I did replace the burnt out 120 ohm resistors a year ago. But no change in behavior -- i.e. that should not have caused the new issue (?). In my debugging tonight, I did open those resistors to simulate their previous condition, but still no go. At least I think I remember they tested open last year.
I'm about to cannibalize this TV, but thought I'd wait and see if the community would have any input which may help me solve this issue. I'm bummed I didn't do everything quickly when things were as expected a year ago.
Thanks & 73,
Timothy
One extra detail, I have since removed the STK392-040, but behaviour is the same.One extra detail, I have since removed the STK392-040, but behaviour is the same.
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Check to ne absolutely certain that all the wires are plugged back in correctly, also if the wires are correct check the resistors near the convergence ICs one or two of them are likely open as well.
check the resistors near the stk's. There are some reports that they get fried when the stk's fry....or the other way around. The resistor ratings are labeled on the resistors. 2.2, 82, 180 or something like that. Also check the board as you turn on the tv. See if any glow red.
Since you said replaced a chip, I presume it was the one STK-393-110 which is used in some models--most of their sets use two chips------I know these sets very well.
I have a offer for you---if you have Yahoo IM we can chat there and maybe find your problem.
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There are two and sometimes three very large IC’s that control the convergence in a big screen set. I think that you have two that are on the board in the center of the set. They are secured to a very large aluminum heat sink. There are two ways to repair intermittent connections on the convergence IC’s. I usually remove the board with the convergence IC’s on them and then and solder the connections. The other method is to tilt the circuit board and solder them while still installed in the chassis. If you remove the board and repair the connections, be careful to remember which connections need to be made when you replace the board. Mitsubishi uses a lettering system, so it should be easy. If the problem remains after you have made the repair, it is possible that the pins on the IC’s have become loose. In this case the IC’s need to be replaced. I have seen this on several occasions. If you choose to repair the set yourself, be very careful of the high voltage that can be stored in the capacitors, and CRT’s. This voltage can be as high as 30,000 volts. I hope this information allows you to resolve this issue. If I have helped you, please help me, and rate this suggestion the highest FixYa rating. (Two Thumbs Up) If you cant rate this post with the highest rating, then please comment to this post and I will try to help you further.
Mitsubishi is famous for this. You are going to have to resolder the convergence ICs. Very simple repair if you are just a little tech savy. Do you know how to solder? This is a 99% fix. Take the back cover off (unplug first). You will see a big heatsink on the board (6-8 inchs long) attached to this are 2 convergence ICs. Unscrew the board, flip it over and resolder all the pins to those 2 chips. Done
5a resistors are all 120 ohm 1/2 watt use flame proof resistors.
check fuse f9a23 or f9a22
also replace knowen bad caps in this unit efecting convergence replace all 10uf @ 16v on the scan doubler module, ther are 8 off them.
make shure and check trace between Rg-8 and r705 for a open, sumtimes fulid from crt will open this up.
regards
daniel.
Your model uses two STK392-570 Convergence ICs, you can get replacement ICs at the following link and they provide free instalation instructions with pictures and free online tech support to help incase you need additional help. Here is the link. http://servicemanuals.vstore.ca/
The IC's you installed will not cause a dark/dim picture......but I would like you to check two things:
1. Make sure you put all cables that you may have unplugged into their proper positions, the cables are marked with numbers, ensure all cables are properly seated,
It sounds like the TV has a Circuit problem in the convergence circuit. If it comes and goes then the concern can be corrected by re-soldering the 'conv' output IC"s. A semi-minor repair and cost.
I apologize none of my formatting came through in the above post.
One extra detail, I have since removed the STK392-040, but behaviour is the same.
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