TECH: Data East CPU board

[John Bennett]

[ukvac] TECH: Data East CPU board
Hi all

I started this collecting lark just after Christmas and have realised
that I
actually enjoy fixing stuff rather than playing with it. As such I
seem to
have gone mad buying "not working" stuff. So far have fixed 3 games
and a
monitor.

I was chuffed to bits when I got hold of a Data East Bad Dudes as I
spent a
fortune playing this as a kid. The games play fine apart from an
annoying
graphics fault on one of the layers. It's almost as if the wrong
background
data is being picked up from one of the ROMs. The image isn't
corrupt, just
wrong. For example, on the title screen, the tall skyscraper on the
left
hand side of the screen is present, but has bits of windows etc from
other
skyscrapers.

I've waffled a bit much now so I'll get to the point. Stimulating
pin 6 of
the 6116 at A10 on the CPU board seems to affect the 'wrong' areas on
screen. Tracing this back leads me to the custom IC at A7. The IC is
labelled as:

L7A0072
DATA EAST
BAC 06
CAE8702

What is this IC and is it replaceable?

Thanks for listening to my rambling.

Pete



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DATA Imported from archives: originally posted by (pete_foster@hotmail.com)

 

[MrMish]

Re: [ukvac] TECH: Data East CPU board
> the 6116 at A10 on the CPU board seems to affect the 'wrong' areas on
> screen. Tracing this back leads me to the custom IC at A7. The IC is
> labelled as:
>
> L7A0072
> DATA EAST
> BAC 06
> CAE8702
>
> What is this IC and is it replaceable?
It is a tilemap generator (there are 3 on Bad Dudes). It is replaceable
as it's common on other boards from this period, but if some of the
skyscraper works then this chip is probably fine. Instead it's likely
to be tilemap RAM (used by this chip to index what graphics to draw) or
the graphics roms themselves having some bad address lines (very
unlikely again). So.. Check the RAM chips near the BAC06 chips.

Bryan



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[system11]

Re: [ukvac] TECH: Data East CPU board
Actually it's pretty unlikely that the 6116 (a SRAM) is causing
incorrect tiles - you'd expect to see corrupt (in some regular way)
tiles if it was that.

I'd be tempted to look at the mame source and work out which roms are
used for background tiles (hint: src/drivers directory), and check that
the address lines of the roms are functioning properly. Verifying them
in a rom reader would definitely be a good idea too. You'll be looking
for constantly stuck, floating, or dead address lines, and if you don't
already have one, you'll be needing one of those cheapy 10 quid logic
probes.

james

On Wed, 2003-02-12 at 16:31, wozzyfozzy wrote:
> Hi all
>
> I was chuffed to bits when I got hold of a Data East Bad Dudes as I
> spent a
> fortune playing this as a kid. The games play fine apart from an
> annoying
> graphics fault on one of the layers. It's almost as if the wrong
> background
> data is being picked up from one of the ROMs. The image isn't
> corrupt, just
> wrong. For example, on the title screen, the tall skyscraper on the
> left
> hand side of the screen is present, but has bits of windows etc from
> other
> skyscrapers.
>
> I've waffled a bit much now so I'll get to the point. Stimulating
> pin 6 of
> the 6116 at A10 on the CPU board seems to affect the 'wrong' areas on
> screen. Tracing this back leads me to the custom IC at A7. The IC is
> labelled as:
>
> L7A0072
> DATA EAST
> BAC 06
> CAE8702
>
> What is this IC and is it replaceable?
>
> Thanks for listening to my rambling.
>
> Pete
>
>
>
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
--
James Greenhalgh <jlist@bloodflowers.org>



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[John Bennett]

[ukvac] Re: TECH: Data East CPU board
> I'd be tempted to look at the mame source and work out which roms
are
> used for background tiles (hint: src/drivers directory), and check
that
> the address lines of the roms are functioning properly. Verifying
them

My first though was address lines on a ROM. I went for the old 'pull
a rom and see what changes' method. I THINK I've found the 2 ROMs
that contain the background data. The address lines on these seem
ok. Strange thing is though, pulsing them seems to make no
difference whatsoever.

> in a rom reader would definitely be a good idea too. You'll be
looking

Duff ROM sprung to mind also. Unable to check this until I've got my
burner built (no way I'm buying one, seen the prices?!). I bought a
Robocop PCB just to see if it was the CPU or ROM board that had the
problem. Guess what? When it was delivered it was a sodding
bootleg!!

> for constantly stuck, floating, or dead address lines, and if you
don't
> already have one, you'll be needing one of those cheapy 10 quid
logic
> probes.

A new probe/pulser was the first thing I bought when I started this
hobby. ;o) It was responsible for my first repair, a Tecmo World
Cup '90 with a duff 4464 DRAM.

>
> james
>



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DATA Imported from archives: originally posted by (pete_foster@hotmail.com)

 

[MrMish]

Re: [ukvac] TECH: Data East CPU board
> Actually it's pretty unlikely that the 6116 (a SRAM) is causing
> incorrect tiles - you'd expect to see corrupt (in some regular way)
> tiles if it was that.
No, I still think that is most likely The tilemap is made up of 16
bit words, with the top 4 being colour and the other 12 the tile. Eg,
if the top bit of the tile (bit 12) was stuck low, then any tiles with
an index above 0x7ff would appear wrong, which is what he's seeing
(occasional but consistent wrong tiles). In fact you could check this
in the Mame debugger by examining the tilemap memory (eg, on the title
screen with the skyscrapers) and seeing what bits are set on the tiles
that appear corrupt on your board.

If the address or data lines to the roms were bad then I would expect to
see corruption inside each tile, rather than correct/complete but
mis-indexed tiles.

Bryan



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[John Bennett]

[ukvac] Re: TECH: Data East CPU board


DATA Imported from archives: originally posted by (pete_foster@hotmail.com)

 

[Alpha1]

Re: [ukvac] Re: TECH: Data East CPU board
Hi,

I have had 2 Bad Dudes boards with similiar faults.

To cut to the chase/get to the point your problem lies in the the boards
connecting to each other.

Totally shit.

You will have to reflow all the joints on those connectors and also reseat
the boards with each other.

oll