TV SYNC SEPARATOR PROBLEMS AND SOLUTIONS:

Fuse blows or TV blows up when sync is disrupted:
This is a problem which is not going to be easy to identify. One possibility is a drive problem. The messed up sync resulting from swtiching channels,or changing input connections might be resulting in an excessively long scan time for just one scan line. However, this may be enough to cause a current spike in the horizontal output circuit or an excessive voltage spike on the collector of the horizontal output transistor. Normally, the HOT current ramps up during scan. During flyback, the current is turned off. This current is normally limited and the voltage spike on the collector of the HOT is also limited by the snubber capacitors to a safe value. If scan time is too long, current continues to increase. At some point, the flyback coresaturates and current goes way up. In addition, the voltage spike will be much higher - perhaps destructively so. Troubleshooting these sorts of problems is going to be tough. However, a likely area to investigate would be:

* Drive circuitry for the HOT including the coupling components.

* The chip that generates takes the sync input and generates the horizontal drive signal.

* A bad low voltage regulator might permit the B+ to rise to excessive levels during black scenes (i.e., video mute during channel changing). Internal fuse blew during lightning storm (or elephant hit power pole):

Loss of Horizontal Sync (also applies to vertical) after Warmup :

The problem lies either in the horizontal oscillator or in the sync system.If it really is a problem with sync pulses not reaching the oscillator,the picture will move around horizontally and can be brought to holdmomentarily with the hold control. If the picture breaks up into strips,there is a problem in the horizontal oscillator. Rotate the hold control:if the frequency is too far off, the picture will not settle into placeat any adjustment of the hold control. Look around the horizontal oscillatorcircuit: all of the oscillator parts will be right there, or check on the horizontal oscillator module. Another horizontal problem can occurif the set is an RCA made from around 1972-1980: these sets are designedto slip very far off sync if the high voltage is too high, to protectagainst radiation. Turning up the brightness will decrease the numberof bars if this system is in question, as the high voltage is decreasing.In this case, check around the high-voltage regulation system on the deflection systems board. I've had 2 1970's RCA's with this problem.(C.P.H.).

Vertical squashed:
This is a vertical deflection problem - possibly a bad capacitor, badconnection, flyback/pump up diode, or other component. None of these should be very expensive (in a relative sort of way). If the symptoms change - particularly if they become less severe - as the set warms up, a dried up electrolytic capacitor is most likely. If they get worse, it could be a bad semiconductor. Freeze spray or a heat gun may be useful in identifying the defective component. It is often easiest to substitute a good capacitor for each electrolytic in the vertical output circuit. Look for bad connections (particularly to the deflection yoke), then consider replacing the vertical output IC or transistor(s). A defective deflection yoke is also possible or in rare cases, a bad yoke damping resistor (e.g., 500 ohms, may be mounted on the yoke assembly itself). The following are NOT possible: CRT, flyback, tuner (except for the famous RCA/GE/Proscan or Sony models where the controller is at fault - see the sections on these specific brands). I am just trying to think of really expensive parts that cannot possibly be at fault :-). Note that some movies or laser karaoke discs are recorded in 'letterbox'format which at first glance looks like a squashed vertical problem. However, the picture aspect ratio will be correct and turning up the brightness will reveal a perfectly normal raster above and below the picture.

Vertical lock lost:
This indicates a picture that is correct but rolling vertically. If the picture is rolling down the screen the frequency of the verticaloscillator is incorrect - too high - and this may be the problem. Generally,the free run frequency of the vertical oscillator should be a little belowthe video rate (of around 50 or 60 Hz depending on where you live). If it is rolling continuously without jumping, then there is a loss ofsync from the sync separator or faulty components in the vertical oscillatorcausing it to totally ignore the sync pulses. If it is rolling up rapidly and not quite able to remain locked, the freerun frequency may be too low or there could be a fault in the sync circuits resulting in an inadequate vertical pull-in range. On older sets, there was actually a vertical hold (and possibly even aSeparate vertical frequency) control. On anything made in the last decade, this is unlikely. There may be Vertical Frequency and Vertical Pull-in Range adjustments (and others) accessible via the service menu. However, if any of these ever change, it indicates a possible problem with the EEPROMlosing its memory as component drift is unlikely. As with everything else, bad connections are possible as well. You will need a schematic and possibly setup info to go beyond this.

REFERENCE:
http://www.stedmundsbury.gov.uk/sebc/play/tvprobs.cfm
http://www.epanorama.net/links/repair.html#tv