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Is that on the break out board? If so it's already centered and the brightness pot is maxed outthere's also the Sub Contrast. I never mess with it, should probably just center it
Is that on the break out board? If so it's already centered and the brightness pot is maxed out
Edit could new pots kill the transistors on the neck board? Also could I use the transistors from a K7900?
Ediit 2 ested neckboard transistors and they are good, not sure what else could cause a loss of color and brightness/contrast


I was watching a zenomorp video and he had a neckboard where like the cluster of resistors by where the ribbon cable plugs in were bad. real obscure failure, but it'll strangle the color signal coming in and will result in bad color output.Sub contrast is on the deflection board (main chassis) by the remote board header. VR800. You can see it in the manual
View attachment 819506
Someone has already mentioned that R811 may be bad. Have you checked that? It should be 75K ohms. Test it out of circuit.
Common failure points on these is U500 (LM1203N) color amp on the neck board. All you can do is swap it out and see. If you have another working U2000, K7400, K7500, or U5000 monitor, you can try swapping neck boards to help troubleshoot.
The new pots won't kill a transistor unless you used the wrong values, and even then I doubt it would.
You should not substitute a K7000 chroma transistor for a K7500.
There is a troubleshooting guide for this you should look at for more help https://www.wellsgardner.com/wp-content/uploads/2016/08/K7400_25_inch-1.pdf
View attachment 819505
R811 is good so that's not it, and I didn't say k7000 I said k7900, I do not have another chassis, this monitor didn't even have one when I got it, so I bought one untested and recapped itSub contrast is on the deflection board (main chassis) by the remote board header. VR800. You can see it in the manual
View attachment 819506
Someone has already mentioned that R811 may be bad. Have you checked that? It should be 75K ohms. Test it out of circuit.
Common failure points on these is U500 (LM1203N) color amp on the neck board. All you can do is swap it out and see. If you have another working U2000, K7400, K7500, or U5000 monitor, you can try swapping neck boards to help troubleshoot.
The new pots won't kill a transistor unless you used the wrong values, and even then I doubt it would.
You should not substitute a K7000 chroma transistor for a K7500.
There is a troubleshooting guide for this you should look at for more help https://www.wellsgardner.com/wp-content/uploads/2016/08/K7400_25_inch-1.pdf
View attachment 819505
This I will check when I get homeI was watching a zenomorp video and he had a neckboard where like the cluster of resistors by where the ribbon cable plugs in were bad. real obscure failure, but it'll strangle the color signal coming in and will result in bad color output.
define issues. you don't know how to white balance? flip TPG to where you have a mostly black screen. the cluster of 3 cutoff pots on the neckboard, turn them up one at a time until the black background turns to the color you're turning up. then turn it back down to where it's black again. before you do that, get brightness where it needs to be. turn the brightness pot on the remote board up until you get grey dots in the black. if you can't get it with the brightness pot, then turn screen up on the flyback, then back the brightness pot off until it's black.Put the old pots back on and kinda have color back but still having issues
i have been messing with the pots and they are not really doing anythingdefine issues. you don't know how to white balance? flip TPG to where you have a mostly black screen. the cluster of 3 cutoff pots on the neckboard, turn them up one at a time until the black background turns to the color you're turning up. then turn it back down to where it's black again. before you do that, get brightness where it needs to be. turn the brightness pot on the remote board up until you get grey dots in the black. if you can't get it with the brightness pot, then turn screen up on the flyback, then back the brightness pot off until it's black.
your colors look muddy, it's probably the tube. see if you can get them to pop more with the contrast pot.
K7900 = K7000R811 is good so that's not it, and I didn't say k7000 I said k7900, I do not have another chassis, this monitor didn't even have one when I got it, so I bought one untested and recapped it
what's more infuriating is I know people that think K7500 = K7000 because they share a K and a 7.K7900 = K7000
your issue is in the neckboard. the flyback doesn't have anything to do with electron gun emissions, it just illuminates the face of the tube. it's why people that jack the brightness up to compensate for poor electron gun emissions don't achieve what they think they're trying to do. I would venture LM1203 reaching 50 C is not correct but be mindful those things run very hot. you can help the cause by spacing the large resistors on the bottom out. (I don't have time to find a visual aid in my vast repository now)so something odd happened, I turned it on and right as I was about to start tweaking the pots the whole picture jumped to a really good brightness, would this be a fly back issue or the lm1203 chip?
Also what is the temp of the lm1203 supposed to be? Mine gets about 50c or more I can't remember
I know which resistors you're talking about and I have already done that, I also put the lm1203 in a socket and I guess I will order a replacement and see if that does anythingwhat's more infuriating is I know people that think K7500 = K7000 because they share a K and a 7.
your issue is in the neckboard. the flyback doesn't have anything to do with electron gun emissions, it just illuminates the face of the tube. it's why people that jack the brightness up to compensate for poor electron gun emissions don't achieve what they think they're trying to do. I would venture LM1203 reaching 50 C is not correct but be mindful those things run very hot. you can help the cause by spacing the large resistors on the bottom out. (I don't have time to find a visual aid in my vast repository now)
Well then I will leave that up to whoever buys it, as I am fixing this thing to selljust play your games
you also don't adjust monitors to TPG, you adjust them to the game you're going to be running