Hi,
I have read your first comment and you have said that there's some instances that the unit power up by repeatedly turning it on and off.
This kind of symptoms is an indication of out-of-regulation condition in the power supply section. It was caused by leaky/dried filter electrolytic capacitor in that section. It will dropped the supply voltage and will disable the unit. In the first stage of the symptoms, warm-up will make itself stable but it will get worst, time will come that the unit will not even power up at all like what you've experienced right now.
Leaky capacitor has a physical indication of fault like bulged/dome at the top and can be easily identify like in this sample picture.
Dried electrolytic capacitor has no physical indication of fault, you must have a capacitor checker/tester to determine its condition.
Check the filter electrolytic capacitor most especially in the supply line of the relay, and in the voltage regulator IC's circuitry.
Hope I helped you.
Have a nice day!
Thanks for using Fixya.
Try this first disconnect the Front Panel Board The one that has power ch- ch+ vol- vol+,then try turning TV on with the remote control handunit if set comes on then problem is in the board.
PTS rebuilts boards 1-800-844-7871
Mitsubishi had alot of problems with FPB most of the time you can replace the switches on board and that will fix the problem.
STK ICs can also shut set down they are big black ICs and will have part number on them
example STK392-570 replace ICs with the same number thats on old ICs
Mats Electronics has them 1-800-628-1118
check all of your fuses and the pico fuses they look like resistors but will be yellow or green
5amps-7amp fuses.
Im trying to think which chassis this one is How Old is the Set?
.Can you tell me how many Big black ICs STKs are on chassis board 2 of them or 4?
Does this set have on other board a STR IC and 2 Big Capacitors? 680uf 200v
Yes you should be able to post picture of boards on this website.
Let me ask you this is this the set that has a Big Metal Box over on the Left hand side, and the powr supply on the right hand side?
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You will open the bacl and if you look where the vertical defection IC is you, can't miss it, because ther will be a very dark or burnt right by the vertical IC, and the IC willnbe fried, too La7838 is the part number for thre vertical IC, and you will have to make some repairs on the fried trace to thre the board too. Very Common on that model.
It will be on the defection board, on a metal heatsink, and it will have seven leggs, and if you resolder the vertical section where the hot spot are that will help.
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On the rare occasion we can get this unit to turn on (by repeatedly pushing the on button and sometimes the remote) The picture is great. I can find nothing burnt on either board. I will admit to having some trouble identifying the vert deflection IC's position.
IC 451 shown on schematic as output V IC to deflection yokes. with IC2V00 as Horiz. & Vert sync.
Board looks good in that area. nothing burnt and no swollen caps. Sorry I failed to mention that the set has turned on once in a while if someone fools with it long enough.
Checked IC 451 carefully on reverse side of PC board. There is no sign of overheating and the solder connections appear to be clean and shiny. I can re-flow the joints and will do so but I'm not convinced this is going to solve my problem. I don't want to put it back together after having found nothing definite.
comment?
Did the re-flow on the 7 connections. Diode D522 is the only thing I found on the entire board that appears to have been HOT. I also did a re-solder on that after checking the diode to determine it was OK..
I'm not convinced that the fix presented to me is applicable to this particular TV since there was no sign of overheating at all in this area. while I appreciate the input I would like another opinion please.
Did all that before contacting Fix-Ya. I researched the problem on the internet too. I've been unable to tie this down with standard troubleshooting techniques. If it sometimes works that eliminates a lot of things but we've been through the easy stuff. I'm looking for what is in the circuit that would stop the set from turning on. Please read what's been done before making additional suggestions - note it's out of the set and on my bench at present so counting the light flashes etc. is not applicable.
Jeeze that sounded harsh - Sorry - It's been a looong day.
Sounds like a totally different chassis.
This one has 2 boards. The one on the left has all the RF - the one on the right has all the power supplies. Is there any way I could send you .jpg's of the boards?
Can't seem to find out how to post pictures in reference to my post.
No big metal box on the left hand side. Just two boards side by side. The power supply board is on the right. I have ordered a new capacitor tester and will attempt to find a bad Cap. in - first the power board and next the signal board. I 've found no instructions on how to post pics on the site.
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