Rca tv issues with vertical hold after resoldering...
Hey guys... me again....
I had this tv that kept shutting off when it would be on for more then 10-15 minuites.....other then that it worked fine....
I pulled the mainboard.. and noted several poor solder connections(some oxidized, some had a ring in them, some only half soldered, etc).
I went ahead and resoldered ALL solder connections.
Now the tv works fine,doesent shut off by itself anymore..
However, i created a new problem....
NOW on some channels or some scenes, the tv clips off the top and botton 2" of the screen(black)...
if i change channels or sometimes even if a scene changes in a tv show then the picture is back to normal. It gets annoying on some channels when the scenes change back and fourth alot. same thing happens from commercial to commercial. It Presents itself mostly with the discoverry channel for some reason....
so either i made a solder connection worse some place or possibly mabye i bridged something someplace....
has this happened to you??????
where should i check next?
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Re: rca tv issues with vertical hold after resoldering...
The only thing I can recommend my freind, since I did not resolder the board, is for you to go over your work with a fine tooth comb. Yes I too, with 38 years experience, have cause problems while resoldering or rushing a repair. Good Luck
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Vertical jumping may have a vertical hold issue, horizontal may have a horizontal hold issue. Most older tv sets will have some knobs or adjustable screws for vertical and horizontal hold. Turn your set on and check for these knobs on the back of your set and adjust until your picture is in as well as you can get it
You will have to search for a TV repair shop, and see if they have another 45" Mitsubishi TV of the same model, or close. You may be able to get a replacement screen from salvage. As for the vertical hold, in some cases you may believe the vertical IC is at fault (we will come back to this), may be not. The first suspicion is in the signal board. The signal board is the board with all the RCA jacks and RF connections. Pull this board out and replace Capacitor (location C2V29) this is a 16 volt 22Mf capacitor. Also replace C2P05 which is a 16 volt 100 Mf cap. This will correct your vertical problem. If you can find an ESR meter, I would certainly check all the capacitors in the signal board. You will find several weak capacitors to replace. The two already mentioned are extremely weak or bad. As for the other board (power supply) you may have to resolder the pins on the vertical IC. It will be located on the corner of the board. I do not remember the location. It is mounted on a heat sink, the vertical IC will have a number such as LA78XX. (LA7838, not sure). Resolder the pins on this IC and check the capacitors in and near this IC. I have not received much problems with this power supply. As always, inspect both boards for bad solder grounds and resolder as necessary! Thanks for asking and show all hands of support!
RCA has had rough time with bad grounds with units similar. You will have to have someone resolder the vertical IC, resolder any grounds on the Flyback and any other IC with heatsinks attatched to them. Also, have them resolder the the yolk connections located on the rear of the picture tubes. This is where you will see two connections that look as if they are weak solder grounds. Good grounds are very important to get your TV operating again! I cannot say enough...have the repair person look at all connections on the bottom of the board and shotgun with the soldering!!! Good luck and thanks for asking!
Your system is encountering a hold down issue. Ussually, this is the absence of signals due to malfunctioning parts particularly in the vertical circuitry.it could Eigther be an IC, transistor or a defective resistor. However, it can sometimes be remedied by simply resoldering the loose components in the circuitry.
I have the same problem-still troubleshooting...so far still not find the cause. DM1 power supply output voltages are operates correctly. Signal output of microprocessor up and down (no good) that turn on Q14105 and latch optical isolator U14102 to power the unit but both of ohmed out ok. it hard to troubleshoot the main board with power on.