My K7000 has "Tails"

supertechnoboy

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I've got a K7901 that's exhibiting some strange behavior. It looks like when the guns go from white to dark during the scan, they're leaving a bright edge, and a "tail" then extends to the raster line above and below. The chassis has brand new caps and flyback. This is a tube swap (A48ABK05X -> A48JQH90X), but I don't feel like that's the issue. Feels more like a transistor problem to me, but I don't know where to look. It doesn't appear isolated to a particular gun. In the photos below, you can see it on the text of the TPG (please ignore purity problem, already fixed), and on the health bars of Altered Beast.

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Yeah, I agree contrast. Maybe a touch of Intensity if the chassis or fly has that.

If that doesn't work, remember, perfection is the enemy of "good enough". Don't break it trying to make it perfect, only to end up fixing it and having the same problem.
 
if the smearing goes upward try turning down the color drives (not cutoffs) on the neckboard
 
if the smearing goes upward try turning down the color drives (not cutoffs) on the neckboard
Thank you. I tried turning down the drives, and it did not change. The weird thing is the smearing is perpendicular to the scan lines, instead of going with the lines like usual.
 
Wild guess: ic1. Controls colors and brightness/contrast

VIDEO INTERFACE AND OUTPUT


The red, green, and blue video inputs come into the monitor at P1. Isolation and attenuation is provided by emitter followers Q1, Q2 and Q3. Forced blanking of the video signals is provided by the circuit of Q4, D5, D6, and D7. The forced blanking causes there to be an interruption in the video signal before it goes to the inputs of IC1. This interruption occurs between scan periods, while retrace is taking place; it is required by IC1. The forced blanking is not necessary for most video signals since they already have an interruption of video (blanking) between scan periods. Some do not; it is to accommodate such signals that the forced blanking circuit is included.


The red, green, and blue signals go into IC1 at pins 2, 4, and


6. Their levels are controlled by the gain of separate channels of the contrast amplifier. The gain is controlled by a DC voltage input to pin 11, which varies with the setting of the contrast control.


IC1 provides blanking of the video during retrace in response to blanking pulses at pin 13, derived from the horizontal and vertical sweep circuits. IC1 also requires a gating signal at pin 12 in order to provide red, green, and blue outputs at pins 21, 19, and 17. If the gating signal is not present, IC1 will not provide video output signals. The gating signal comes from IC2, pin 12 and is derived from horizontal sync.


The brightness is varied by varying the DC level of the outputs at pins 17,19, and 21. This is accomplished by varying the DC voltage input to pin 14.


The video outputs from IC1 are provided via R30, R31, and R32 to the neck board where they are amplified by the video output stages Q201, Q202, and Q203 before being applied to the cathodes of the CRT through R10, R11, and R12.
 
Wild guess: ic1. Controls colors and brightness/contrast

VIDEO INTERFACE AND OUTPUT


The red, green, and blue video inputs come into the monitor at P1. Isolation and attenuation is provided by emitter followers Q1, Q2 and Q3. Forced blanking of the video signals is provided by the circuit of Q4, D5, D6, and D7. The forced blanking causes there to be an interruption in the video signal before it goes to the inputs of IC1. This interruption occurs between scan periods, while retrace is taking place; it is required by IC1. The forced blanking is not necessary for most video signals since they already have an interruption of video (blanking) between scan periods. Some do not; it is to accommodate such signals that the forced blanking circuit is included.


The red, green, and blue signals go into IC1 at pins 2, 4, and


6. Their levels are controlled by the gain of separate channels of the contrast amplifier. The gain is controlled by a DC voltage input to pin 11, which varies with the setting of the contrast control.


IC1 provides blanking of the video during retrace in response to blanking pulses at pin 13, derived from the horizontal and vertical sweep circuits. IC1 also requires a gating signal at pin 12 in order to provide red, green, and blue outputs at pins 21, 19, and 17. If the gating signal is not present, IC1 will not provide video output signals. The gating signal comes from IC2, pin 12 and is derived from horizontal sync.


The brightness is varied by varying the DC level of the outputs at pins 17,19, and 21. This is accomplished by varying the DC voltage input to pin 14.


The video outputs from IC1 are provided via R30, R31, and R32 to the neck board where they are amplified by the video output stages Q201, Q202, and Q203 before being applied to the cathodes of the CRT through R10, R11, and R12.
is that the Google AI? lol

@supertechnoboy it could be a byproduct of the tube swap. is the convergence/yoke set right? also K7000s are old school enough that brightness/screen could have contrast-like properties in how they appear. try turning brightness down.
 
I haven't changed the filter cap yet, so I'll order a voltage regulator and filter cap, just to be sure the power is rock-solid. I'll order IC1 at the same time, and we'll see what we find out!
 
dude there's nothing wrong with the filter cap. if it was actually bad you would know it.

it's also not going to fix your problem.
 
dude there's nothing wrong with the filter cap. if it was actually bad you would know it.

it's also not going to fix your problem.
I'm sure you're right--my thinking is that maybe there's variation in b+ that could only be seen with a scope. (I have a scope, but I'm not sure how much variation is normal.) I've seen posts discussing blooming issues that were caused by a weak filter cap, and I do have some of that also.
 
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