Help with Minor R-Type graphics issues

[Pelly]

Well I believe this to be minor...

Anyway, there are what appears to be vertical bars affecting only some background graphics.

In the screens attached you can see it affects the Warning text screen, Ram check and title screen (not shown). In the other screen shot you can see that during game play the bars knock out parts of the stage graphics as it scrolls however no sprites are effected when they pass over it.

Some basic things I have tried:

• Re-seated daughter board
• re-seated all EPROM's
• piggy backed a number of the worker RAM's
• one at a time removed some of the EPROM's while running to see if they effected the issue. No luck..

Planning to do more on this soon, dump and check EPROM's etc.. but I am mainly posting this to see if anyone else has come across the issue before and can narrow down my area of investigation..

Thanks.

 

[Apocalypse]

Faulty custom chip on the bottom board?
Don't panic, @caius has reproduced them.

Or maybe RAM issue.

 

[jassin000]

I'm no expert, but I would think if it was RAM you would still get sprights they would just be garbled/wrong.
The fact the sprights are missing at repeating locations seems like failing custom.

 

[Pelly]

Faulty custom chip on the bottom board?
Don't panic, @caius has reproduced them.

Or maybe RAM issue.

Yeah ok cool.

The other obvious thing I haven't tried yet is swapping the bottom board with another working R-Type PCB set. I will do that and see what happens.. If its not RAM on the bottom board the likely a custom I suppose.

Thanks

 

[-Ace-]

Check the voltages. I had sprite issues until I bumped up the +5 voltage.

 

[Apocalypse]

I'm no expert, but I would think if it was RAM you would still get sprights they would just be garbled/wrong.
The fact the sprights are missing at repeating locations seems like failing custom.

Check the voltages. I had sprite issues until I bumped up the +5 voltage.

From what I read sprites are NOT affected, only background.

 

[Pelly]

I'm no expert, but I would think if it was RAM you would still get sprights they would just be garbled/wrong.
The fact the sprights are missing at repeating locations seems like failing custom.

Check the voltages. I had sprite issues until I bumped up the +5 voltage.

From what I read sprites are NOT affected, only background.

Yes, and checked my voltages first up. All game sprites seem fine. Its just some of the background being effected by these vertical bars as seen in the pics.

 

[-Ace-]

I'm no expert, but I would think if it was RAM you would still get sprights they would just be garbled/wrong.
The fact the sprights are missing at repeating locations seems like failing custom.

Check the voltages. I had sprite issues until I bumped up the +5 voltage.

From what I read sprites are NOT affected, only background.

I had sprite issues- background was fine-

 

[caius]

It seems only backgrounds are affected.The BG circuit lies entirely on bottom board.As @Apocalypse said I've reproduced a custom which is used for tiles generation but the problem could also be elsewhere.Usually these Irem boards suffer from bad Texas Instruments TTLs which fail like the Fujitsu ones.