Image wobble

[Retroman839]

Got this annoying wobble in the image
I’m not using a line filter so wondering if it’s that?

Or caps or something els any ideas massively appreciated thanks in advance ..
(I haven’t reflowed chassis either)

Apolagies if vid isn’t clear
Also when a flash of white takes place on screen image kinda jumps then settles back all in a split second
Will try getting better vid tomorrow

 

[Retroman839]

After a little research
I found a promising thread /artical about these chassis

Here it is

That R318 mod was made to change the source for VCC to the vertical circuit. Prior to that the supply came from the flyback, if the monitor was used with a gun game, each time the gun was shot the high white flash would cause the highvoltage to jump. This in turn would cause the vertical VCC to jump and result in a jumpy picture vertically. The resistor from D306 to the empty hole ar R318 should be 680 ohms. I developed the mod and have a rough sketch if you need it e-mail me, I will scan it and e-mail it back to you.
Rick@niemandisplays.com
As far as the vertical foldover goes, change C318, it causes weird stuff when it is off value, everything from foldover, jitter and collapse.

Hope this helps.
Rick

This sounds very much the same as my symptoms if not identical .
Does this fix sound correct ?
Anyone don’t this ?
I have emailed the guy and I’m going to
Locate c318 and swap for a new.
Check for cold solder joints.
And attempt the mod.

 

[Lurch666]

I got bad wobble on the side of a monitor when using a cheap switching PSU.
Changing the power supply eliminated the issue.

 

[thegreathopper]

I had similar on a Aero cab, it was the internal step down causing the problem - odd thing it was fitted by Sega.

Moved to external all good.

 

[Retroman839]

Cheers for this ,,
I’m getting screen jumping when a white flash in game screen fills with white for a second , like in shooting games.. but when screen fills with white
The image jumps then resettles

 

[Retroman839]

I have the shcimatic for ch-288 pentranic .
And I mod to stop the screen jumping.
( jumping not wobble . Wobble is the psu as lurch mentions ) It says R318 is tied to the v.cc of the chip

and the other leg is tied to the flyback. When a white flash appears on screen too much H V is coming from
Flyback causing screen to fly up then settle back down.

So the mod lifts the leg of the resistor and with a wire connects it to D506
My question is which side of the diode do I connect the wire to ?

I am assuming the right hand side
But I don’t know.


I’m ok with the resistor because obviously one leg goes the the chip leg.

I have purchased 10 c318 a tantalums 2.2uf 16v Apparently it’s fussy as soon as this tiny little cap goes screwy

 

[thegreathopper]

Excellent, so now working ok?

 

[Retroman839]

Excellent, so now working ok?

No I haven’t done it yet waiting on the
Tantalum cap.
I don’t know which side of the diode to make connection too either ?

This chasssi I am using a Samsung 29
a68qcp891x100 tube from a
Samsung Plano Tv Set
I compared a Thomson’s yoke values today And it was very close too
I will add Thomson tube code tomo
And will try to test the chassis on the thompson too asap