MT to R-Type problem

[Rossyra]

Getting a weird issue all of a sudden with my Major Title conversion. Occasionally the sprites flicker, disappearing in horizontal lines. It was fine when I originally did the mod

I double checked the mods and they are as detailed in Paul Swan's instructions. Only difference is I have a compatible Cypress 70ns RAM chip installed (cy62256ll-70pxc). Could this be the problem?

Rossyra2012-11-30 03:01:06

 

[IDCHAPPY]

In my expert opinion, I'd say possibly

 

[cliff_poole]

Are the missing lines flickering ?, if so, it does sound like it could be a RAM failure.

I have seen MT boards suffer from dry joints on the big surface mount customs, so it might be worth having a go at pressing down on those, see if it changes anything.

 

[Macro]

faster should not cause any problems in most circuits, unless the data is present before the game expects it, but if timing is that critical they usually buffer the data via a clocked latch to keep everything in sync.

I have a conversion here that has one black line through the sprites that I need to look at this weekend, so will let you know what I find in case it helps you with your problem

 

[Rossyra]

I'm not explaining it very well, I don't have missing lines, I just have sprites that flicker, the problem gets worse the longer the PCB is running.

Occasionally I get some flickering rows of pixels on the left hand side of the screen.

 

[Rossyra]

Thanks for the replies, I ordered some different RAM too just in case, it was only a couple of quid.

 

[karlcdoe]

I guess a video of the artifact might help if swapping the RAM out doesn't fix it. I would speculate that if it worked for any length of time after it was converted then the conversion was okay and the board has just developed some random fault. I had an MT that had some random graphics fault that Chris Hardy kindly fixed for me ages ago and that was a bad contact on one of the surface mounts.

 

[Rossyra]

Good shout, I should get the RAM tomorrow, I'll report back with a vid if it doesn't cure it.

 

[Bods]

We had lots of problems with atm machines at work, some of the I/O cards used Cypress Memory chips on them, others had a different make

In the end it was the Cypress chips causing the issues

 

[Rossyra]

I put the new RAM in, the flickering sprite stopped flickering, and the backgrounds started flickering instead

When I put the Cypress chip back the flickering stopped altogether. I'll have to check the soldering later and maybe reflow it.

 

[Rossyra]

it looks like this might be voltage sensitivity as well as RAM timing. Game runs 100% in my Jamma cab with the old RAM. If I put the new RAM in I get background glitches.

In my NNC I get flickering sprites with the old RAM. I haven't messed with the 5v, but I assume that is cause.

I've bought even more RAM from China to test further, will take a couple of weeks to arrive.

 

[Rossyra]

The problem is back, no mattter the voltage, cab or RAM.

Anyone have an ideas? I've double-checked all the wiring mods.

 

[Rossyra]

It's clearer if you watch it in the higher res on youtube by the way. Particularly on the worm at the end.