Mr.Do! corrupted sprites

[vsl]

Hello, friends!
I'm trying to solve a problem with Mr. Do's sprites!
I'm uploading a video because I can't explain it properly.

Thanks in advance

 

[vsl]

sprites are damaged when there are two or more on a vertical line

 

[sukhbir]

May possibly be the counters(74ls161) near to the sprite rams.
Look in the schematics there are two sprite rams close together, the counters outputs the address bits to the sprite rams.
You can try piggyback the 74ls161 with a good chip.

 

[vsl]

I did this with all 8 pcs. 161 but no change
maybe I should take them off?!

 

[sukhbir]

Piggy backing logic chips don't always work,to be sure it's best to use a oscilloscope and scope the outputs.

 

[vsl]

yes I checked them with the oscilloscope and all inputs and outputs look good but ,
F6 G6 F7 G7 the only thing that struck me was that the clk signal varied from 2.2 mhz to 4.2 mhz ..

 

[philmurr]

What results do you get from the test ROM / built-in test?

 

[vsl]

after the test it tells me that ram and rom are ok

 

[vsl]

I left the board running, after a while (2-3 hours) the sprite problem disappeared.


I also found another strange problem:

this also happens when touching ic F9,F8,G8

 

[sukhbir]

That's got to be a floating pin,the colour proms run hot possibly legs are tarnished.

 

[vsl]

The problem with the sprites was solved. It turned out that the exact 5 volts that I always use measured at the far end of the boards are not enough. I raised them to 5.15 volts and the sprites were fine.
Thank you sukhbir and philmurr for your help!

 

[vsl]

New problem,
during the game everything is fine until the sprites on the screen become more and the sound is starting to break. then the game slows down incredibly much. I checked the processor frequency and it is a constant 4 MHz. The eproms are fine and it is not one of them. I see something like this for the first time. Could you tell me where I can check.