Replacement for single-chip Defender Video Decoder

[david_orton_2000]

Wow - I hit the max length for a subject!

Ok, anyone know:-
(1) If it is possible to dump this ROM, and if so, how? Is a BProm or some other oddness?
(2) Any ideas on how to make a replacement. In Mame and later Defender CPU boards there are 2 Video Decoder Roms...

-I've emailed Dave Langley (the Defender Jedi), however no reply just yet so maybe he's on hols or buried in Pinball madness! (eeek).

Cheers,
DaveO.

 

[tb lilley]

Bi Polar P ROM.

You can buy replacements here if you want to go that route: Link

 

[Equites]

What kind of 0.6" pitch PROMs are these?

 

[david_orton_2000]

24 Pin B-Prom.

DaveL has emailed me recently, apparently this Prom can be read using a 2716 setting on an Eprom reader, so I will try that. He also has given me more to check, etc. I will update the thread on progress.

 

[Judder]

Ha - that's been on my reading list on my iPad for the last week

Here's how to read them as 2716's as far as I can tell and I'm building an adapter like this at the moment

http://forums.arcade-museum.com/showthread.php?t=257897

and to use 2716's in place of them you have to ground a couple of pins as per Bob Robert's again (*second time I've quoted him in 5 minutes

)

http://arcadecontrols.com/BBBB/decoder.html

The Harris 7641 datasheet with pinouts for reference is here

http://pdf.datasheetarchive.com/indexerfiles/Scans-004/Scans-0097024.pdf

and the 2716 for comparison

http://pdf.datasheetarchive.com/datasheetsmain/Databooks-5/Document241492.pdf

Hope that helps

 

[Judder]

So continuing my thoughts on this, I've been thinking of making a daughterboard that allows a programmed 2716 to be put in the top, and then plugged directly into the socket on the CPU board where the decoder ROM should be.

There's a 2532/2732 adapter that was published on Elektor a while ago which is _really_ simple so making a PCB layout for the 7641 to 2716 should be really easy.

"Many old pieces of equipment contain type 2532 EPROMs, which are currently difficult or impossible to obtain. If the software has to be modified or the EPROM fails, it is in principle possible to replace the EPROM with a modern 2732, but this has a different pinout. A handy hobbyist can of course make the necessary modifications to the circuit board, but it is more convenient to use an adapter board that can be fitted in place of the 2532. The main circuit board can then remain in its original state."

http://www.elektor.com/magazines/2000/december/2532-2732-eprom-adapter.56639.lynkx

Anyone got any experience of finding someone to manufacture a low volume run of a board if I made the PCB layout?

 

[Judder]

FYI this is the example of switching a 2532 with a 2732 and they're charging 12 Euros odd just for the PCB (gulp!)

http://be.eurocircuits.com/shop/Offtheshelf/product.aspx?&ano=004076-1&ad=9930&lang=en&r=elektor-pcb-service

 

[chadsarcade]

I thought the usual way was to program a 2832 or fast 2732 with 4 x images and add a couple of links to the solderside of the socket...?

ETA: Link is >here<
chadsarcade2013-09-25 13:16:54

 

[Judder]

I thought the usual way was to program a 2832 or fast 2732 with 4 x images and add a couple of links to the solderside of the socket...?

ETA: Link is >here<

Yes that is what Dave has on his site too, but I was trying to find a solution where you don't modify the motherboard, just either the chip or build an adapter between the two

 

[Judder]

...but I was trying to find a solution where you don't modify the motherboard, just either the chip or build an adapter between the two

To be clear for future references we are discussing two separate areas here in one topic

As Dave said in his original question

"(1) If it is possible to dump this ROM, and if so, how? Is a BProm or some other oddness?
(2) Any ideas on how to make a replacement. In Mame and later Defender CPU boards there are 2 Video Decoder Roms.."

So as regards 1. that's where we are all talking about either making a wiring harness or a PCB which makes the required pin connections to read a 7641 decoder PROM as a 2716 EEPROM, as lots of EPROM programmers can read 2716 EEPROMs, but very few can read 7641 PROMs.

As Chad says for 2 there is the ability to replace a 7641 decoder PROM by burning a 2716 EEPROM with 4 x the contents of a decoder ROM and then either re-route some wires on the chip, or via modifying the board, to allow the 2716 EEPROM to behave like a 7641 decoder PROM.

Dave Langley's site has all the possible permutations of Decoder ROMs (Rom 4 and Rom 6, Rom 2 and Rom 3 etc.) and also covers the early Defender boards which only have 1 Decoder ROM (Rom 1 or Rom 2 IIRC)

Hope that helps!

 

[Muppz]

You need to knock up something like this, a bit of veroboard, a zif socket and some pin strip. Reads as 2516 on my dataman S4.

Chad should recognise it, we used it when we dumped the defender decoders back in the late 90's when we were developing/re-engineered Williams replacement stuff like FRAM modules and single chip rom boards and sound boards.

 

[Mitchell Gant]

Chad should recognise it, we used it when we dumped the defender decoders back in the late 90's when we were developing/re-engineered Williams replacement stuff like FRAM modules and single chip rom boards and sound boards.

So, what are these single chip ROM and sound boards of which you speak?? Sounds interesting, would you care to describe in more detail?

 

[Muppz]

If memory serves it borrowed heavily from (sean riddle?) work that was circulating on the net at the time to make a defender romboard with a single rom and a CPLD to do everything else, it got as far as veroboard prototype that pretty much worked. I was also working on a replacement soundboard that played music during attract mode etc and was stereo. I think Chad had approached a musician to see if they were interested in the project and to write an original piece, again veroboard proto but I got fed up with VAC and sold up most of my stuff and buggered off to NZ. I've recently rediscovered lots of stuff in boxes that last saw the light of day 12 years ago...

I also had a full pacman design in FPGA minus z80. Now other folks seem to have done the same thing but a few years later.

Sorry for hijacking the thread btw, just answering the question