Centipede PCB fault with vertical movement problem

EclipseEye

Well-known member
Joined
Oct 18, 2010
Messages
1,594
Reaction score
102
Location
WARRINGTON, Warrington, United Kingdom
Centipede PCB fault with vertical movement problem - SOLVED

Dudes

I've been busy fixing 2 Centipede PCBs for a friend, one has been fully repaired and is now off the repair pile.

The second one needed more work, the PCB was completely dead and had numerous issues including no sound. I have now got it almost working but have stumbled on the last fault that I need to clear in order to take it off the repair pile.

Pictures speak a thousand words, so a video must speak even more;



Any idea of where to look for this problem? I have already gone over the Object Movement Circuits (Horizontal and Vertical) and have not been able to locate the problem.

As you can see the PCB is running in attract mode, and the movement is fine until the Archer moves up or down. When it does move vertically, it moves in blocks like a really old 70's video game, along with it, it seems to affect the vertical position of the Centipede when it does.

Any help is really appreciated as I have already spent alot of time on this particular problem.
 
Last edited:
I would check the LS32 at C5 and/or the LS163 counters at A5 and B5.

Brian

Thanks Brian

I had previously checked those ICs, the only difference I could see between the working PCB and this PCB was on the LS32 at C5 at pin 10. On the working PCB this pin was pulsing, HI was solid and LO was rapidly flickering on the probe. However, on this faulty PCB the pin 10 was clearly solid on HI and LO.

I did also test C5 against a logic comparitor and it passed as OK.

Pin 10 is an input pin which comes from LS42 at H3 on pin 6. I did also check the LS42 was functioning correctly.
 
If you play a game, does the centipede/spider move up and down with the archer as you move the trackball?

Brian
 
If you play a game, does the centipede/spider move up and down with the archer as you move the trackball?

Brian

Hi Brian

I'm running the PCB on a Supergun and do not have a trackball :(

So, I'm guessing the erratic vertical movement of the Centipede and Spider is tied to the Archer. I say this because if I coin her up and start a game, the game plays perfectly because the Archer is not moving.
 
Ok

I finally solved this. Brian was quite on the money, it was a bad LS163 counter at B5, pin 14 was stuck HI.

I had been using a logic probe, lazy on my part as I only normally use this to find floating pins.

This time I got out the Scope and it clearly showed that pin 14 of B5 was stuck HI. This was impossible to see with the probe as it looked like pin 14 was pulsing correctly.

Many thanks guys for the help.
 
Back
Top Bottom