I have a Slvania 27" tv that had no vert deflection I replaced the vert. ic and got the picture back, but now I have an over scan on the top 1/3 of the screen. Mod # STR22278 (CHIP REPLACED WAS A "LA78041") it seems like a bad cap. in the vert. cir. any quick fixes
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Re: vert deflection problem
You are correct about having a dry or leaky capacitor that is causing those lines to show on the top of the screen.
Check the caps with low capacitance like 1uf, 10uf, 47uf, etc.
No quicker fix for this one until you change the capacitors.
Hope this helps.
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It could be the vertical output IC, but there may be other possible causes which include:
- bad solder contacts on deflection yoke connectors or dirty connector contacts (on the circuit board and / or on the picture tube neck)
- bad solder contacts on the vertical output IC or associated components (check for little cracks in the solder around the pins, these are so called "cold" or bad / broken contacts)
- power loss to the vertical output IC - check for any burned resistors or other components around that IC, assuming you know which one it is - see which ICs are connected to the wires going to the deflection yokes (coils) on the picture tube neck and check them well.
You need to resolder any bad contacts, clean any dirty pins on the connectors and replace any burnt out components (assuming you can still determine the type or value of the component).
Since you mentioned the problem occurs once in a while, this means that the IC probably fails when it warms up, which can often happen if there are loose connections or bad solder contacts.
Anyway, it could turn out to be a faulty IC, i just suggested a few other things that can be fixed quite easily, and possibly without the need to replace any of the components.
I think you are describing 'no vertical deflection.'
If all you have on the screen is a single horizontal line, the vertical deflection circuit (or IC) has died.
Unless you have service documentation on hand, I can't give a part number to replace but this is typically not an expensive failure and if the set was OK before, it is worth having repaired.
There are some components in the vertical deflection circuit area that are failing. An experienced TV service man should be able to troubleshoot and repair this for you. It could take several hours of labour cost.
Vcc is on Pin 6 of the vert. output IC so you can trace that back to it's feed resistor (not sure the location number but you can find it easily by following the circuit trace).
Depending on what your problem is you may need to replace some
electrolytic capacitors as well. Follow pin 7(pump up) back to it's electrolytic
cap. and look for swelling or bulging. Look for other bulged capacitors in the vertical section. You may also identify a bad resistor by a discolored look but not always, if in doubt meter it. Let me know if you need some more info.
Vertical deflection circuit has a problem. Overwrapping is from a
bad electrolytic capacitor. The vertical coil is the larger of
the two coils around the CRTs yoke. Follow its two wires down to
the connector on the main board and follow the traces there to get to a
heat sinked IC with maybe a dozen pins on it. (Get the service
lit if you want but this is how I do it) This is the I.C. that
drives the vertical deflection. Replace all the caps in the
Hope Ya Fix It!
Since Intermitant always inspect the vert ckt for bad solder connections. If not replace the output IC they're cheap and most likely the problem If you still have lines on the top or bottom I would replace all of the electrolytic capacitors in the vert ckt also. Without much test equipment rebuilding the whole little ckt is the best way to go.
If hitting the set gets the vert to come back then you have bad solder connections on the vert. outputs.. If it dosent then your gonna need to measure the voltage first on the vert output IC see if its about 24 or so volts If it is replace the IC. If its not the replace the vert B+ drive capacitor off the flyback xformer. If you cant find these things then your gonna need to get a schemtic from sams photo facts and post the vertical section and I will tell you or assist youin this repair. If you have had experience in soldering and curcuit work your already ahead in the repair. post the schematic.
Defective components in vertical deflection and output circuit inclusive of vertical output device, coupling capacitors, and yoke connectors. Passive devices such as electrolytic capacitors, coils, and resistors to/from power supply circuits. If your tele is more than 10 years old dump it and get a newer product. $100 USD is a fair price to diagnose and attempt service, depending on age and configuration. Older products may not have replacment
parts available at any repair cost.
There may be a pot for adjusting the vertical size. If so, it may be dirty. If you can find it, try adjusting it which could clean it. BE CAREFUL -voltages are very high.