K7000 red overdriven

curtislv426

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Hi guys. I'm working on a 25 in k7000 chassis that smears the red. I gave it a full capkit, reflowed the video header pins, replaced the red chroma transistor (q201), and q1 on the chassis. Both tested good but replaced anyway. Didn't fix it. Replaced the red pots. Didn't fix it. Swapped the neck board with a known working one. No change. Replaced ic1. Nope. Replaced the green capacitor that sits at the front of ic1 which goes to pin 1 and pin 22 because another member had this same problem and that fixed his overdriven red problem. No change. The chassis has a new flyback on it but I didn't know the source so I put in one from APAR. No luck. The tube is good. It's my test tube and I checked it with my bk and tried another working chassis on it just to rule that out.

I'm going to start the my journey through the red circuit. I was hoping someone else might be familiar with this issue though to save me some time. If not, I let ya know what I find.
 
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One thing I would suggest is to swap Q1 with either Q2 or Q3 and see if the issue changes to Green or Blue. I've see those transistors cause crazy things like this.
 
One thing I would suggest is to swap Q1 with either Q2 or Q3 and see if the issue changes to Green or Blue. I've see those transistors cause crazy things like this.
Thanks man. I also went ahead and replaced q2 and q3 during my troubleshooting when I was scratching my head. I forgot to mention that. I appreciate your help.
 
Thanks man. I also went ahead and replaced q2 and q3 during my troubleshooting when I was scratching my head. I forgot to mention that. I appreciate your help.
You're welcome. So if it's nothing on the neck board, IC1, Q1, or the tube...that's about everything that would normally cause it. Time to go component by component starting at the RED header pin. Could be a leaky zener diode.
 
check those green chiclet caps. I had a K7000 from a wet NBA Jam cabinet that looked like animals tried eating the monitor. it had the blue driving weird, it was one of those caps broken off. otherwise I would never question zeno's advice on such a matter. LOL
 
So far I've noticed that d5 reads differently in circuit than it does from another working chassis and from d7 and d6 as well. I get a .583 voltage drop with black lead on the cathode but when I switch the leads with black on anode I get an O.L. On the other diodes and the working chassis I get a 1.928 when I switch the leads . I replaced the diode and the new one reads the same as the old one in circuit. . I should have some time late tonight to make my way through each component In the red circuit.
 
You may simply be overdriving the red gun. Have you tried doing the white balance adjustment in accordance with the manual?
Or, easier is to follow Zenomorp's (Mike's Amateur Arcade Monitor Repair) video on K7000 white balance. I've misplaced the link.
 
You may simply be overdriving the red gun. Have you tried doing the white balance adjustment in accordance with the manual?
Or, easier is to follow Zenomorp's (Mike's Amateur Arcade Monitor Repair) video on K7000 white balance. I've misplaced the link.
Yes. I'm very comfortable with properly adjusting the colors. This is definitely something else.
 
Yes. I'm very comfortable with properly adjusting the colors. This is definitely something else.
Thanks for clarifying that.
You didn't mention whether or not you have an oscilloscope. It would certainly be helpful to track the RGB signals to determine where the problem first appears.
One other thing you could try is swapping the red input to the neck board with the green or blue to see if the problem moves with it. Would help narrow it down to a problem on the main board or the neck board.
 
Thanks for clarifying that.
You didn't mention whether or not you have an oscilloscope. It would certainly be helpful to track the RGB signals to determine where the problem first appears.
One other thing you could try is swapping the red input to the neck board with the green or blue to see if the problem moves with it. Would help narrow it down to a problem on the main board or the neck board.
I swapped neck boards and the problem remained
 
I love wild ass guesses. One moment and I'll outline how far I've traveled through the red circuit.
 
Ok. Here's how far ive traveled so far. I replaced c1, c2, and c3 because my transitor/ component tester couldn't read those caps. I replaced c7 as well early on because i saw that fixed another persons same problem. I have been lifting legs on every resistor i come to to get an accurate reading.
k7000-red-path.jpg
 
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Well, the good news is you have eliminated most of the input side of the circuit, so there's not much left to check.

Looks like mostly resistors left? Those don't fail often, but I would maybe start suspecting them, at this point.
 
You didn't mention IC1 after @zenomorp mentioned it. If you don't have a spare you can unsolder input pins 2 (Red) and 4 (Green) and then add a quick jumper from C4s output (red) to pin 4 and see if the RED works on the Green gun..
 
You didn't mention IC1 after @zenomorp mentioned it. If you don't have a spare you can unsolder input pins 2 (Red) and 4 (Green) and then add a quick jumper from C4s output (red) to pin 4 and see if the RED works on the Green gun..
He said he replaced IC1 in the original post.
 
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