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CPS1 Graphics Issues - Forgotten Worlds


WhiteCrow

Question

Hi everyone. I'm new the forum, and stumbled across the wealth of CPS1 information here while troubleshooting a Forgotten Worlds PCB to be used in a dedicated FW cabinet restoration I'm working on.

 

While cosmetically the board is in incredible shape (probably the cleanest CPS1 set I've ever seen!), it has had numerous issues. When first fired up, it would play music shortly, and then go into the self-check which it seemed to pass. It was difficult to see for sure as the text is completely scrambled. The graphics also were very glitchy with blocky red artifacts. This is also unfortunately one of the older CPS1 versions with awful QFP mask roms on the B board.

 

Using a known working A board from a Strider set I was able to isolate the problems to the B board, which cleared up the red junk, which presumably is an issue with the A board I'll worry about at a later date. :) I pulled and dumped any EPROMs I could, and found two bad ones in the set, both 27C1000's, which I reburned successfully. Unfortunately the graphics and text are still scrambled, and it locks up completely when loading the first scene of the demo loop. Physically everything looks great. The traces and legs of the customs and logic seem in perfect shape, and the sockets are clean. I swapped the compatible PAL (LWIO) from Strider to the FW B board with no noticeable effect.

 

Here's a link to a video of what it looks like currently. Excuse the vertical orientation, as it's plugged into the Egret 29 at the moment.

https://www.youtube.com/watch?v=bCRNkSfCQb8&feature=youtu.be

 

 

I'm at the point now where I don't quite know where to look next, and am starting to suspect that one of the HN62404FP-18 might be bad, which would be really unfortunate, as I gather there's no replacement. Before resorting to a conversion or emulation for this dedicated cab, I figured I'd ask some of the resident CPS1 experts here if they have any insight. Thanks!

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It is highly likely to be the QFP mask ROMs on the really old CPS1 B boards, there is no direct replacement as these were custom ICs produced with the data already built in.

 

I do have a project underway that will provide a solution for these boards so if you can hold off on converting it there may be a way forward.

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Actually the HN62404FP 4Mbit surface mounted MASK ROMs can be programmed, datasheet here:

 

 

https://4donline.ihs.com/images/VipMasterIC/IC/HITA/HITAD052/HITAD052-1087.pdf?hkey=EF798316E3902B6ED9A73243A3159BB0

 

You can still found for sale but you must be lucky to find some really old NOS devices and not pulled ones.Anyway, to help a friend of mine some months ago I designed a small adaper for reading/programming these devices as 27C400 :

 

RSCN4501.jpg

 

But sadly all the devices he bought were already programmed although they looked new/unused

 

For example you can find them on Jotrin:

 

https://www.jotrin.com/product/list?keyword=hn62404fp#details

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Oh, wow. Caius, I didn't know those mask roms could be programmed. Do you have an adapter for sale by any chance? It might help me troubleshoot this board.

 

Yes, I have many adapter PCBs but until now I could not test them because I have been not able to find any NOS MASK ROMs.All the ones I found were pulled.

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you'll never find any, they just do not exist.

mask roms are produced in the factory using a lithographic process and delivered ready.

There is no possibility of programming with a programming device................

 

Like the datasheet says , the HN62404FP is a programmable MASK ROM.Someone successfully repaired a Ghouls 'n Ghosts by programming them:

 

https://translate.google.com/translate?sl=fr&tl=en&js=y&prev=_t&hl=it&ie=UTF-8&u=http%3A%2F%2Farcade-area.lebonforum.com%2Ft2815-ghouls-n-ghosts-us-1st-rev-ppu-hs-resolu&edit-text=

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Like the datasheet says , the HN62404FP is a programmable MASK ROM.

that means it is an eprom or OTP with a mask rom compatible pinout.

 

------------

The data in mask roms is unchangeable hard wired.

Mask proms are much cheaper to produce than eproms

That's why they are used for data that does not need to be changed anymore, eg for graphics.

 

For program data uses eproms, because here the contents can still change

 

This practice can be seen on many boards.........

Edited by DonkeyKongler
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that means it is an eprom or OTP with a mask rom compatible pinout.

 

------------

The data in mask roms is unchangeable hard wired.

Mask proms are much cheaper to produce than eproms

That's why they are used for data that does not need to be changed anymore, eg for graphics.

 

For program data uses eproms, because here the contents can still change

 

This practice can be seen on many boards.........

 

The HN62404FP is an OTP device with a MASK ROM pinout.It can programmed (or also replaced if you will wire it to the PCB accordingly) as a 27C400.

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Update on this:

 

Thanks to Bonky on http://arcade-area.lebonforum.com/ I received a salvaged Forgotten Worlds B board that had many of the bad HN62404FPs. LW-05 was bad on both, so that one is still out of action for me. These are incredibly failure prone devices.

 

I did try programming HN62404FPs from multiple sources, and as expected, none are blank. After asking for advice, I also don't believe Willax ever used a HN62404FP he programmed to fix his board in this thread: http://arcade-area.lebonforum.com/privmsg?folder=inbox&mode=read&p=43658.

 

I think it was a existing G&G pull sent to him by Bonky, so it is unlikely that these are possible to find blank if anyone is considering going that route. My only chance right now seems to be wiring in one of Caius's adapters holding a 27C400 to the pads directly to see if that will do the trick. :)

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