19K7901 vertical collapse

Doughbroz

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I'm still lost in this new forum setup, sorry if this has been answered recently. Picture is collapsed down to a very narrow horizontal line. Remote board is connected, vertical height pot is working according to voltmeter, new cap kit, solder joints look good. Don't have a flow chart for this one, but from 7000 and other charts I know voltage should be tested somewhere before replacing ICs, but don't know where. Using 7000 chart I know pin 6 on IC3 should have 24 volts, which it does, but don't know if that works for the 7900. If any of the ICs should be replaced next, what are the part numbers? Also, several of the caps in the new B.R. kit were lower voltage than the originals. Supposedly the 7900 uses the same cap kit as the 7000, and nothing exploded when I powered it back up, so I ASSume that is correct. And if anyone can spare a flow chart for the 7900, please PM me. Thanks
 
unsolder, insoect, and reflow r98-r101..

#101 if notorious for actually tarnishing the copper trace UNDER the solder... to the point it loses electrical connection..

that bieng the case, unsolder, if black scrape clean again, then resolder..


not saying thats it for sure but usually if you have deflection issues thats the general area where you find a problem...

also recheck all solder, especially around any and all pins (yoke pins, video input, etc)
 
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monitor

First check your yoke plug and measure the two wires close to each other in the plug and see if you have a resistance of 15 ohms or more( i forget exactly) if not you might have a broken sollder joint at the yoke itself or at the board pin solder joint. I have seen the vert. ic go bad but test good compared to others.
 
First check your yoke plug and measure the two wires close to each other in the plug and see if you have a resistance of 15 ohms or more( i forget exactly) if not you might have a broken sollder joint at the yoke itself or at the board pin solder joint. I have seen the vert. ic go bad but test good compared to others.

forgot about that ic..
although usually its obious when they go bad though...get a nice burn mark in the center
 
Thanks for the replies. It will be a while before I have time to work on this thing again, but I will try your suggestions.
Edit: Which is the vertical IC?
 
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Resistances at the pins on the yoke itself are 2.2 and 6.9, after deducting 0.6 ohms for loss in the meter leads. Reflowed the connections on the yoke with no change. No amount of jiggling or poking on the wires changes the readings, so I doubt there is a bad connection there. No short between the pairs either, so if that 15 ohm resistance figure is accurate for the 7900, then the yoke is bad. Anyone positive about that number? Thanks.
 
After all this time, I finally noticed that the manual labeled for a 7901 is actually for a 7500 series. Thus, I thought R101 was supposed to be 6800 ohm(which it is pretty close to), but the original is actually supposed to be 9800 ohm if I can still read a color code chart(white, gray, red). Meaning it is shot. So, can anyone point me to a source or proper description for this 9800 ohm 3 watt resistor. Looking for it on Mouser is making me crazy. Thanks
 
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