Mr Do's Castle - odd character display

JDGJr

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RESOLVED!! - Mr Do's Castle - odd character display

The unicorns and hittable blocks in the attached image have lines thru them - not aways the same lines, but never correct. Likewise some of the ladders seem to shimmer. The background and score page is always correct. I did notice that the 'castle' on the logo screen shows oddities for the first several seconds after the machine is powered on. All machine tests pass.

I've removed all the removable chips and cleaned the pins, and removed them a 2nd time to make sure i hadn't bent any pins.

Does anyone know if this is an EPROM issue, or a RAM issue?
Does anyone know which EPROM are used for graphics?

thanks for any info,
John
 

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Last edited:
I have the same exact problem with mine. I'm not currently using my PCB, so I didn't invest any time to work on the problem. If anyone has any input on a resolution, I'd love to hear it as well.
 
lines in video

Sounds like a ram problem. Try piggy backing a same type ram on top of your rams and see if you get your video lines to change and or clear up. If so, then you narrowed it down to the ram.
 
Resolved!!

Try piggy backing a same type ram on top of your rams...

piggy backing?

I tried to place chips over the existing one, simply bending the pins slightly to make sure i got good contact. Not being overly patient, i did 4 at a time. On the last 4 chips, the display was PERFECT. Then removed 2 and bad again. Removed 1 and moved the other - bad. moved to test the last possible chip, and perfect again.

H6 is definately bad!

thanks for the suggestion!
 
Last edited:
Must be something about these boards or the RAM chips. I had a second board that showed a similar, but worse, issue. Same technique worked, and after replacing B7 and E7, the display is perfect.

thanks again, gurus!
 
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