Main > Monitor/Video Forum
k7000 19" screwy color behavior
nfabozi:
Not sure if the issue is similar but I wanted to mention it. I have a game with blotchy color that looks like this:
I found out that if I move these magnetic beam adjusters, I am point it one with my yellow flat head screw driver (don't know the terminology), the image started to clear up
Here is after
I still have some adjusting to do but wanted to mention my finding if at all related to your issue. I could not see all of your picture very well. The lines in your image are probably from the screen adjustment on the flyback being turned up too high.
snappleman:
--- Quote from: nfabozi on August 09, 2021, 06:27:37 pm ---The lines in your image are probably from the screen adjustment on the flyback being turned up too high.
--- End quote ---
The lines only appeared on the red signal on that one part of the screen, that was due to open resistors before the red chroma transistor. I replaced the damaged video IC and everything is perfect and working well now:
Hard to take photos of CRTs but the image on this one is spot on, no color issues, even the convergence is mostly on point all around the screen.
I'm not sure exactly how this happened to the board in the first place (among the other issues it had since it was broken), but this seems like it started from the IC, taking out the resistors and the transistor? Whatever the case it's working well now.
The only remaining question I have is if can I safely move that large cement resistor that's by the filter cap and affix it to the heatsink just like the other resistor? I want to fit this board into a TV and I don't like that resistor being up that close to the tube, if I use some heavy gauge heat resistant wire maybe? If that's not a good idea maybe slapping some kapton tape on the tube around where the resistor is?
lilshawn:
glad you are sorted out. :cheers:
any number of things can cause it. static can build up and discharge through the IC killing a color. a failed driver tranny can short in such a way as the 80 some odd volt color drive voltage gets back-fed into the IC blowing the channel. it happens. make sure all the grounds are hooked up and it's fine really.
and that resistor is fine. it doesn't get hot enough to do anything to the tube anyways. i suppose it might be keeping the cap next to it slightly hotter than it would be so otherwise... the amount of failures on the k7000 i've seen in the last 14 some odd years... related to something like that, is currently zero.
old caps, dead STK's and fried transistors are about the only things I've ever had really consistently happen.
snappleman:
:cheers: It feels good to finally actually fix something after a lifetime of destroying everything I touch B)
MKFan4Life:
Just happened across your post. Noticed you had weird values for R7, R8, and R9 (according to the parts list or schematic). I have been double-checking everything on my 25" K7000 while waiting on a replacement for C44 I found shorted.
Well, my R7, R8, & R9 are reading like yours. I thought they were bad parts, although I figured resistance would go up, not down. Seems that the parts list on the two K7000 PDF's I have looked at are either wrong, or I am missing something.
The paragraph above the parts lists say the parts are the same across all K7000's unless otherwise noted. Then afterwards I do see smaller sections listing certain specific parts likes caps & resistors for the P447 (19" as I understand it) and the 25" models, which I think are usually P538, although my 1990 chassis has no designation like this, but it has a long number on the underside including 5357P-007, and a sticker designating it's a 7197 on top of the HOT heatsink.
I had replaced a VR, STR 30130 last year on this chassis when my MK1 cab. It ran fine except it needed new caps, as the last kit I did was from Bob Roberts about 10 years ago. Well, I was playing it and adjusting the flyback one night, and the entire cab shut off. Blew the main 3 Amp fuse in the cabinet. I disconnected the monitor and the cab ran fine blind after replacing the fuse. Reconnected the monitor and realized the 2 Amp chassis fuse had bit the dust also. Replaced it, and it immediately blew again, but I cut the cab off fast enough to save the main cabinet fuse.
After taking the chassis out to examine it, I ended up replacing the HOT which was shorted, doing a cap kit from Arcade Parts & Repair, and then I found the STR 30130 I had installed last year was shorted, too. Luckily I had bought several VRs last year, so no problem. I was about ready to install a fresh VR (removed it from circuit, just like HOT, & they both still tested shorted) when I decided to start checking for shorts/bad parts and found that cap C44 shorted.
While awaiting that cap, I found those resistors way out of spec apparently. I think, as you do, they can't all 3 be low on resistance to almost the exact Ohm value. Did you ever find out why there was that difference in the three resistor values in the parts list/schematic you had?
(Sorry so long-winded.)
:-\