obitus1990
Well-known member
K7000 - 19" P447/P456. Missing red. I know, plenty of these threads, flowchart, zenomorp videos, etc. -- I've read them all and have been working on this chassis all day long.
Recapped, reflowed the entire neckboard, reflowed all problematic areas on the main chassis, INCLUDING signal input header and the small header (P201) that connects the color wires from the chassis to the neck board and its source from P6 on the chassis. Checked continuity of aforementioned wire between neckboard pins on P201 and the P6 connector on the mainboard to make sure the wire wasn't broken - it isn't.
Tried different game boards, different harnesses and a test pattern generator -- all have no red.
Swapped color transistors on the neck board -- no change
Swapped color transistors on main board - no change
Pulled all of the transistors and tested them via diode test and all passed.
Pulled and tested the red drive and red cutoff pots, also verified the right ratings were in the right positions (2Kohm vs 200 ohm).
Checked continuity of neckboard socket to make sure the RED pin was connected (pin 7) in the socket to the solder tail on the back side of the board, and it's good.
Tested the chassis with another tube, it has the same problem, tested another known good chassis on this tube, it works fine -- problem follows the chassis.
Turning up the red drive to maximum (or was it the red cutoff, I cannot remember -- maybe both did? ) will make the screen turn completely red - so according to posts by mecha, this means the problem isn't with the neck board.
About the only thing I have not done is swap IC1, because I don't have one on hand. I also don't want to spend $12 plus shipping on this IC if it's not the problem. Is there anything else I'm not considering here? All the passives in this circuit look to be OK and test within spec, in circuit at least. Is there a way to test IC1's functionality without pulling it and replacing it?
Recapped, reflowed the entire neckboard, reflowed all problematic areas on the main chassis, INCLUDING signal input header and the small header (P201) that connects the color wires from the chassis to the neck board and its source from P6 on the chassis. Checked continuity of aforementioned wire between neckboard pins on P201 and the P6 connector on the mainboard to make sure the wire wasn't broken - it isn't.
Tried different game boards, different harnesses and a test pattern generator -- all have no red.
Swapped color transistors on the neck board -- no change
Swapped color transistors on main board - no change
Pulled all of the transistors and tested them via diode test and all passed.
Pulled and tested the red drive and red cutoff pots, also verified the right ratings were in the right positions (2Kohm vs 200 ohm).
Checked continuity of neckboard socket to make sure the RED pin was connected (pin 7) in the socket to the solder tail on the back side of the board, and it's good.
Tested the chassis with another tube, it has the same problem, tested another known good chassis on this tube, it works fine -- problem follows the chassis.
Turning up the red drive to maximum (or was it the red cutoff, I cannot remember -- maybe both did? ) will make the screen turn completely red - so according to posts by mecha, this means the problem isn't with the neck board.
About the only thing I have not done is swap IC1, because I don't have one on hand. I also don't want to spend $12 plus shipping on this IC if it's not the problem. Is there anything else I'm not considering here? All the passives in this circuit look to be OK and test within spec, in circuit at least. Is there a way to test IC1's functionality without pulling it and replacing it?
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