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I have schematics for this model and want to do a DIY repair. I believe the problem is a faulty capacitor in the vertical deflection circuit that is causing white lines/inverted picture interlaced at the top of the screen. All i need to know is where on the board the capacitors are located so i can replace them
Re: where are the vertical deflection caps located
Check C421, C427 and C429. These capacitors are located nearby IC401. IC401 is mounted on a heatsink and has the following markings on the body LA78041
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You have bad capacitors in the vertical deflection. You will need to replace capacitors that are near and next to the vertical IC. These models very, but they all seem to have the problem you have. You did not specify a particular model. But in general you will look for under sized electrolytic capacitors. They are, in my opinion, too small to carry the load in the vertical deflection. Pay attention to the caps and there locations. Once again this model may be a little different than the one I have repaired. C417 is 50 volts at 4.7 Mf, C446 is 50 volts at 22Mf, C441 is 50 volts at 100 Mf, and C513 is 50 volts at 1 Mf. You will note how tiny these are, and so, please check all of the smallest ones with an ESR capacitor checker. The caps and locations I give, are enough to correct the problem you describe. I have repaired several of these. All are similar, and may have
slightly different locations in the models, but they seem to be of the same values. Thanks for asking and show all hands of support!
Depending on the model, on most CRT type TV units, a single (left to right) line indicates failure of the vertical deflection circuitry. Almost always this would be caused by a faulty vertical output IC. Repairs involve replacement. It most be noted though that in some instances, similar symptoms maybe exhibited by:
cold solder on any of the pins of the IC or related components;
leaky or dried up capacitors;
absence of the +20VDC supply from the secondary of the FBT.
Options then are:
consider a DIY (do-it-yourself) repair if and only if very familiar with electronic components & circuitry, use of a DVM/VOM, a soldering iron/station and safe working practices with high voltages. Access to a Service Manual or at the very least, a schematic diagram would be an advantage;
should you be uncomfortable with a DIY, perhaps your best bet would then be to seek the services of an authorized Service Center (specially if still under warranty) or a qualified professional.
This denotes a problem with the vertical deflection circuit. This is more then likely the result of the vertical coupling capacitor failing. You will need the schematic diagram of the TV to find the capacitor in question. it is located between the vertical output stage and the vertical deflection winding of the yoke transformer. In addition check the continuity of the vertical winding of the yoke transformer this can cause the same problem. In any event the problem is that the vertical deflection signal is not getting to the yoke transformer or the yoke transformer is malfunctioning.
If this is a CRT television, replace all electrolytic capacitors in the vertical circuit - this fixes 90% of all vertical deflection problems. The capacitors most likely t0 fail are low-cap, high-volt such as 3.3 uF at 50 volts, etc. Quicker and cheaper to replace them all, rather than tracing it down to the one bad part. Total cost if you do it yourself is about $15 tops, and make sure you install them correctly - electros have a plus and minus lead, and must not be installed backwards or you'll have serious blow-upage of the new parts. Before replacing the caps, however, go over all solder joints in the vertical section, reheat them and add a touch of fresh solder. You may end up not needing to replace anything.
The symptoms you describe are actually 2 different issues. The easiest way to address this is to attack the vertical problem then if the other still exists, we will address that one. I should be able to provide you with details, but I will need the model number. Please update this with the model number and further details and instructions will follow.
Hi,
Get service manual / schematics from HERE and find why vertical uotput IC is blown in your TV.
Service Manual will also give you info how to perform vertical adjustments.
Hope this info will help you to resolve problem.
Look for the vertical IC. It should be a small flat IC attached to a heatsink and marked something like LA7837. The IC will have a circuit designation like ICxxx. For example IC301. Check all of the caps in the same circuit (C3xx). One or more are bad &/or intermittant. Start there and keep us posted.
Dan
You have a bad vertical output IC, or the sweep power supply that drives the IC is bad. Your going to need the service schematic diagram and the know how to fix solid state electronics.
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