G08 Woes -- Bad custom IC? -- PICTURE

p1001

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Working on a few Sega games tonight. I came across a monitor issue that I've never seen before. Picture is warped on the bottom. The farther down the more skewed it gets. Deflection and HV look good. Everything else checks out within spec. I'm now thinking that it's a bad custom IC. Anybody seen this before?







IMG_3355.JPG
 
Have you tried a different timing/control pair to drive that monitor or at least are you running a verified good set? Every G08 I work on seems to have a loose yoke.... is that yoke on straight?
 
Hi Pat. Had to chuckle when I saw your post. This monitor is in the Space Fury I got from you last year. I'm just now getting around to fixing it. The boards are good, they're my test rig. I've never had a loose G08 yoke before. To make sure I double checked it and it's tight. The symptom doesn't point to an out of position yoke anyway. Something is effecting the signal globally. It's either on the input side or in the error correction. I'm going to walk through the input side and see if I can pinpoint where the signal goes bad. One thing that Mark suggested today was the input protection board. That is one thing I did not check last night so I'll start there. Stay tuned.


Have you tried a different timing/control pair to drive that monitor or at least are you running a verified good set? Every G08 I work on seems to have a loose yoke.... is that yoke on straight?
 
I finally had time to pull the G08 yesterday and track down the problem. Remember I suspected the input protection circuit or the custom chip. Well, here's the final verdict on this repair. Turns out I was pretty close. Input protection board checked out ok. I began to probe the vertical deflection (6xx components) and the glitch was consistent throughout the circuit. The fix came from a pair of odd components. Turns out that R601 and C703 on the deflection were loose and removed from the error correction circuit. I replaces them and touched up the cold solder joints on P900 and bingo, solid as a rock.

Hi Pat. Had to chuckle when I saw your post. This monitor is in the Space Fury I got from you last year. I'm just now getting around to fixing it. The boards are good, they're my test rig. I've never had a loose G08 yoke before. To make sure I double checked it and it's tight. The symptom doesn't point to an out of position yoke anyway. Something is effecting the signal globally. It's either on the input side or in the error correction. I'm going to walk through the input side and see if I can pinpoint where the signal goes bad. One thing that Mark suggested today was the input protection board. That is one thing I did not check last night so I'll start there. Stay tuned.
 
Thank you for the follow up.

I have been batching a lot of g08 repairs of late(mostly making fire and smoke!) but had no clue what was up with yours. This will help for future repairs I am sure.
thanks!
 
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