Pac had no moving graphics.

Marc_NJ

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My Ms. Pacman board stopped working the other night with lots of guests in the house.

Found my problem listed here; http://www.arcadegameover.com/pactrouble.html


"No characters on screen. Dots can be seen being eaten. "


I am confused in that 2E had a trace under it connecting P7 to P10, yet this web site lists that as a problem??

I was going to do the hi/low tests too, but am questioning the accuracy of that web site.

Any tips?

Thanks
 
Full snip from website;

No characters on screen. Dots can be seen being eaten. Caused by interfering or grounding databus RA0 thru RA5.

These can be found on 2A,2B,2C,2D p2,3,4,11,12,13, or 1E p11,12,13,14 or 2E p13,14.

2B p1 is high, or p2&3 or 3&4 or 4&5 shorted.

2A p12&13 or p11&12 shorted.

2E short pin7 to p10.

1E, 2E p15 shorted to p 11,12,13,14.

3D Bad or Removed.

3A, 3B p1 low.

3B p1 short to p8.

Signal 3E p6 to 3A,3B p1.

2F 10,13 low.
 
I believe what they mean is that a short between those two pins could cause this issue.
As in those two pins should NOT be shorted.
As in probably a bad chip at 2E.

Of course the short could be elsewhere shorting those two pins, but there's a start anyways.
And this is my interpretation. (same thing for the 3B description)
 
I believe what they mean is that a short between those two pins could cause this issue.
As in those two pins should NOT be shorted.
As in probably a bad chip at 2E.

Of course the short could be elsewhere shorting those two pins, but there's a start anyways.
And this is my interpretation. (same thing for the 3B description)

There is a copper trace between those 2 pins, so they are supposed to be shorted, no?! I doubt a copper trace magically appeared the other night. :)
 
The pins on the chips run extremely close to traces. Those pins can get shorted to the traces. Check to make sure none of the pins on 2E are bent and touching the trace next to it.

Jeff
 
The pins on the chips run extremely close to traces. Those pins can get shorted to the traces. Check to make sure none of the pins on 2E are bent and touching the trace next to it.

Jeff

Pulled the chip to check all the traces.. Put it back in, re soldered and checked with a meter. No short.
 
There are two LS283 on the bottom of the board. Trying to remember off the top of my head here.... Thats not an uncommon issue and im pretty sure most of the time its a bad LS283 in row 2. I will check my repair logs and see, had a couple with that issue just recently.
 
There are two LS283 on the bottom of the board. Trying to remember off the top of my head here.... Thats not an uncommon issue and im pretty sure most of the time its a bad LS283 in row 2. I will check my repair logs and see, had a couple with that issue just recently.

Binary Adder... Any way to test it?
 
My memory sucks...from repair log.

1. Symptom:
No Characters on game screen. Dots can be seen eaten.

Solution:
Bad 3F 74S89 Ram

Of couse this isnt set in stone, it just happened to be the issue with this particular board.
 
My memory sucks...from repair log.

1. Symptom:
No Characters on game screen. Dots can be seen eaten.

Solution:
Bad 3F 74S89 Ram

Of couse this isnt set in stone, it just happened to be the issue with this particular board.

Same question, how do I test? :)
 
A logic probe and a copy of the schematics.

Riyeet..

I use my Tektronix 2232 as a logic probe. :)

Looking at the schematics, I'd have to probe both CS (Pin 2) and WE (Pin 3) and look for some activity on the data bus "DR" (Pin 5, 7, 9, 11) when CS is low, and WE is high... Right?? Or is there an easier way?

Thanks!
 
"No characters on screen. Dots can be seen being eaten. "


I am confused in that 2E had a trace under it connecting P7 to P10, yet this web site lists that as a problem??

There's at least a dozen different issues that could lead to 'no sprites'... that site is far from exhaustive, and only identifies one such possible cause, which apparently isn't the cause on your board....
 
My memory sucks...from repair log.

1. Symptom:
No Characters on game screen. Dots can be seen eaten.

Solution:
Bad 3F 74S89 Ram

Of couse this isnt set in stone, it just happened to be the issue with this particular board.

Did the piggyback on 3F, no change.. any other ideas?
 
Did the piggyback on 3F, no change.. any other ideas?

Before anything else check 3E ( 74LS20 ) pin 1,2,4,5 see if they are pulsing and then see if pin 6 pulses. If the other pins are pulsing and pin 6 is stuck low sprites will be hidden, so replace 3E.

But real quick tests, run through to check the writing to sprite RAM and match output.

1. check the outputs from 3F and 3H see if you're getting any pulsing on pins 5,7,9,11,
no pulsing then.. check 5N pin 6 see if that's pulsing, no pulse then check pins 4 and 5 see if they're pulsing which the probably are if you're getting a normal display, and then replace 5N ( 74ls08).
No pulsing on pins 4 and 5 then check for broken traces.

2. During gameplay check 3F and 3H pin 3, see if you're getting pulsing ( writes to the sprite RAM )
no pulsing replace 7M

3. check the match output from 3E ( 73ls20 ) see if pin 8 is pulsing
no pulse then it's most likely a faulty 74LS283 at 1F or 2F

4. check "CNTR LD" pin 9 of 1E and 2E ( 74LS163 ) that should be pulsing.
no pulse then trace 'match' through 1H, 5N, 4B and 2C. Plus 3P and 2P which also
control the CNTR LD.

If all that looks good you'll have to start looking downstream to the sprite line RAMs ( 1A,1B,1C,1D or 2A,2B,2C,2D ) the multiplexers 3C or 3D and 3A, 3B

- James
 
2. During gameplay check 3F and 3H pin 3, see if you're getting pulsing ( writes to the sprite RAM )
no pulsing replace 7M


- James

Thanks so much for this detail James!!

I did your tests, and found that 3f and 3H Pin 3 is high all the time.. Checked 7M Pin 10, it is also high all the time.

I pulled a LS139 out of a non-working board I have here, and did a piggy back for 7M. No change. Maybe the one on the board had a short and I need to pull it?? Maybe my "spare" is dead too (got it from a dead board).. As soon as I hit send, I think I will pull 7M from PacMan board and do a real replacement.. Will report back.
 
Replaced 7M, no change.. So either my replacement is bad too, or I have something else going on..

7M Pin 15 seems to stay high too.. so, no enable.

Source is 7J, but that multiplexer also controls the buttons and movement. That all seems to work! So, I am guessing 7J is good.
 
Are there no sounds either ? If 7M's pin 15 never goes low that would point to 7J being a problem.

- James

Sounds seem fine... I just pulled a 138 off of my "parts board", and did the piggy back. No change. Will now pull 7J and swap it for real.
 
Sounds seem fine... I just pulled a 138 off of my "parts board", and did the piggy back. No change. Will now pull 7J and swap it for real.

Ok, if you're getting sound 7M also controls the sound writes. So 15 must be enabled at some point.

- James
 
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