Help With K7500 - Vertical collapse?

gobsgraham

Member
Joined
Mar 26, 2009
Messages
649
Reaction score
17
Location
AB, Canada
Help With K7500 - Sync issues.

I bought two "untested" chassis off of a fellow KLOV'er knowing that they may not work. One of them needed a cap kit really bad and I was able to get it nice and bright but I can't get the second one working.

- It came to me missing the vertical output IC.
- I added one and inspected for cold solder joints. Powered it up and I got a picture that is what I would call partial vertical collapse. It has the bright line in the middle and then about 4 inches of green screen that is garbled.

- I did a full cap it on it and it did not change anything.
- I tried a different remot board aswell at some point throughout this process.

Do the K7500 chassis have a few common problems that could cause this. I know the MS8-26SU chassis have a problem with C433 and R433 or something that do so I was hoping there was a quick fix out there for the K7500.

Thanks
 
Last edited:
Check U601 Pin 9 for +25vdc. If nothing, check R303 as it may be open.

Otherwise, U601 might be bad.

Other parts to check:

R618, C616, C613, C610, Q602, and of course the Vertical Pots on the remote...
 
Thanks Mod. I finally had a chance to test some things last night. I had 25V and the other parts tested fine also. So taking Fromm's advice I replaced U601 again and it fixed the vertical collapse problems.

Unfortunately, now I can't get it to focus. I can get it to hold vertically and horizontally and can see the colors and lines but I can't actually read anything. The game then boot and the screen colors are all messed up.

I will continue down the chart and check Q700, Q601, U701, +5@ U702:14, Z700, R705. If you somebody sees the pictures and has any more advice I am all ears.
 

Attachments

  • P1070178.JPG
    P1070178.JPG
    51.3 KB · Views: 15
  • P1070179.JPG
    P1070179.JPG
    39 KB · Views: 13
  • P1070180.JPG
    P1070180.JPG
    44.2 KB · Views: 12
  • P1070181.JPG
    P1070181.JPG
    55.3 KB · Views: 11
Those all look like horizontal hold/sync issues. Are you running it with a medium-res signal? How is your sync hooked up?
 
It is a medium res signal. When I shut down and flip the dip to standard I can't get it to stabalize at all. When it is set to medium, I can stabalize the picture on the boot screen when it is detecting the hard drive partitions but just not readable. I think this means the hold is good but the sync is bad.

I did have the machine fully functional with a different chassis but had to steal the good chassis when I sold my spare machine. Now I am having a Superbowl party and was hoping to get this other chassis going for it.

I just picked up a spare dead (R106 is blown up) chassis of Ebay so I have a few spare parts to try flipping stuff. Alternatively I could take the T101 and R106 off if the sync problem chassis and try to repair the new dead one. It may need a new width coil also as the housing broke in transit. I should be able to get one of them up and running.
 
Back
Top Bottom