Centipede video noise, intermittent trackball

mikejmoffitt

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I got a Centipede recently and have been cleaning and fixing it.

With the mikesarcade 2 1/4" trackball rebuild kit, the trackball does not roll well. The rollers seem like they are not as thick as the originals, and aren't making very good contact. I may try another kit.

Periodically, I'll lose Y movement (up/down). After around 30 seconds - one minute, it'll drop vertical movement for about five seconds, and then it'll come back. I've swapped pokeys, and I've tried moving the encoder wheel by hand. It is too regularly intermittent to be just loose wiring or a bad contact on the board I think.

The other problem is that there are small visible sparkles in the video output that correspond directly with CPU activity (dense at the top of the raster, sparse except for a few interrupt handles partway through the screen a few more times).

I haven't replaced the big blue or worked on the ARII yet, so that is the next step.

Has anyone seen these issues?

b8uyCr3.jpg


The screen control was turned up a bit to make the issue more visible for the photograph. Normally the black area is properly black, and you can see the speckles more faintly.
 
Not likely an AR issue. Don't waste money on a rebuild kit. The original parts are fine, as long as your voltages are all correct. Don't shotgun parts on these, as if it's a power issue, you can measure and verify that, before replacing anything. Are all of the DC voltages correct on the game board? (+5, +12, and -5V). Post them here, to two decimal places.

Similar with the big blue. Measure the AC voltage on the 10.3V DC test point on the AR. If it's less than 1V AC, the big blue is fine.


Sounds more like a board problem. What does test mode tell you? (See the manual if needed.) It may or may not give you clues, but it's the first place to check.

The trakball and video issues are likely unrelated. The trakball input buffers on the game board often fail, causing trakball issues. Swap the opto boards in your trakball, and see if the problem changes axes. If so, it's the TB optos or wiring. If not, it's the game board. Clean the optos out with a q-tip also, as they can have issues if they get really dirty.
 
Thanks for advice on the AR. Voltages look good at the board, so I guess it's doing fine.

I forgot to mentioned that I did swap this board into a friend's Centipede cabinet, and it had no problems there. No video speckles, fully behaving inputs. Next time I may bring over my trackball and see if it misbehaves on his machine or not.

I will clean the opto boards. They looked okay at a glance, but some dirt could be hiding from me.
 
Test the AC on the 10.3V test point. A bad big blue has been known to cause all sorts of weird stuff, so that, combined with the fact that the board appears to play ok in another cab, are definitely relevant.
 
I moved the plugs between the two optos on the trackball, and the problem moved to the horizontal. So, the problem probably lies there. I'll inspect that more this weekend.
 
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