k7500 center line issue (solved)

kayzp4ul

Active member

Donor 2021, 2023
Joined
Dec 6, 2020
Messages
353
Reaction score
237
Location
California
I'm working on a K7500 chassis right now. It's almost all the way functional, but it's very finiky right now and would like some advice. I've done a cap kit, with filter cap and now my monitor is displaying a center line. I can get a full image, but any minor tweaking and I lose all progress if that makes sense. My guess right now besides double checking my recap job would be that it's the flyback since that's the only thing that I didn't replace. Any advice would be awesome!
 

Attachments

  • IMG_0616.HEIC_compressed.JPEG
    IMG_0616.HEIC_compressed.JPEG
    784.1 KB · Views: 19
  • IMG_0625.HEIC_compressed.JPEG
    IMG_0625.HEIC_compressed.JPEG
    891.3 KB · Views: 19
I'm working on a K7500 chassis right now. It's almost all the way functional, but it's very finiky right now and would like some advice. I've done a cap kit, with filter cap and now my monitor is displaying a center line. I can get a full image, but any minor tweaking and I lose all progress if that makes sense. My guess right now besides double checking my recap job would be that it's the flyback since that's the only thing that I didn't replace. Any advice would be awesome!
the flyback is doing what it's supposed to. if it's an original flyback I would refrain from doing anything with the focus or screen adjustments. it's merely my own theory but mucking with those is what may cause the drifting focus/screen brightness. I've noted in some threads that gamefixer and I ring tested some original bad flybacks and they had faults on the same pins, so I'm guessing it was a design flaw.

that all being said however, try to gently bend on the V. Size and V. Hold pots on the remote board and see if that affects the picture at all. you might have a cracked pot I would guess. if that does nothing then try bending on the ribbon cable at the remote board and then at the deflection board. it's not something I've seen but maybe there's cracked solder to the vertical adjustments. there's a K7400 at work where the remote board harness traces lifted on the deflection board, so you'd plug the cable in and the pins pop out the bottom. whoever worked on that thing before me had a multi tiered case of not knowing what they were doing, it was a nightmare to straighten out.

report back with anything you might find. @zenomorp may have seen this before, I've been through a number of K7400/7500s and this is new to me
 
I rechecked my solder work and forgot to snip a leg from a capacitor (rookie mistake). However, the the negative leg and everything around it is connected to ground so it didn't matter anyways.

I checked r303, r402, d603, d302? As well as the vertical ic by d603. All checked good.

I'm going to hook this chassis back up and mess around with the cable and report back here within an hour.
 
Solved

I hooked everything back up and noticed that the monitor was turning off constantly by itself. Checked B+ voltage and it was at 121v. Adjusted the pot back down to 117v and now I have a stable image with no center line. My only problem now is that the image's width doesn't span the full width of the screen. I'm assuming the transistor needs to be swapped?
 
Solved

I hooked everything back up and noticed that the monitor was turning off constantly by itself. Checked B+ voltage and it was at 121v. Adjusted the pot back down to 117v and now I have a stable image with no center line. My only problem now is that the image's width doesn't span the full width of the screen. I'm assuming the transistor needs to be swapped?
the middle heatsink where the HOT is, there should be a white red black wire harness to a red plug. did you plug it into the width transistor in the corner?

EDIT: the white wire goes on the left leg of the transistor. I had a visual aid but it's in a vast repository and not easily accessible right now.

EDIT AGAIN: I lied, it's still documented here https://www.arcaderepair.net/wells-gardner-p719-neckboard/ lol

IMG_20130831_173508_zps3a0df1d2-copy-1.jpg
 
Last edited:
Back
Top Bottom