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View Full Version : Unmoddable neo ??



HPMAN
11-28-2000, 03:14 PM
Welll, I modded some neos with an arcade mod recently, and today I tried one more with no success... http://www.neo-geo.com/ubb/frown.gif

I use the double stack method, but when switching to the debug bios (I use a switch), the neo responds as if there was no bios at all http://www.neo-geo.com/ubb/frown.gif

Putting back the eprom to programmer, it seems erased ?!?!

Neo serial # is NEO-AEC #048284, mainboard is labelled NEO-AES3-4

Any idea ??

JMKurtz
11-28-2000, 03:59 PM
Are you sure the BIOS was programmed properly, or when you tried to read it in, all the pins were making good contact, especially the one that you pulled up for the switch?

Also, when you solder the chip to the pre-existing one, make sure to disable the old one properly and also make sure all your solder contacts are good and clean.

The Neo isn't capable of erasing an eprom -- UV Light is needed to do that.

Jeff

HPMAN
11-28-2000, 04:32 PM
Originally posted by JMKurtz:

The Neo isn't capable of erasing an eprom -- UV Light is needed to do that.


That's what seems strange to me... http://www.neo-geo.com/ubb/redface.gif

I'll do further tests today and reportresults a little bit later...

HPMAN
11-28-2000, 05:19 PM
Well, I tried the bios on a neo (NEO-AES3-5), works fine (I don't solder eprom directly, I use a eprom socket), put it on the other neo (NEO-AES3-4), neo acts as if there's no bios...

Putting back the bios on the other neo, it still works fine.

So the problem must be from the neo, I cheched soldering points, everything seems OK.

Any idea ?

HPMAN
12-03-2000, 06:25 PM
Just putting this tread on top in hope of some help... :/

JMKurtz
12-04-2000, 09:09 AM
You put the original BIOS back into this other Neo and it works.

You're not using an AMD chip, are you. I've see some AMD chips that worked in some systems, but not others.

Just an idea.
Jeff

HPMAN
12-04-2000, 03:06 PM
Well, yes, I tested with an AMD chip and it doesn't works. Same with a NEC chip.

Should I test all my AMD chips ?

Anyway, thanks for the help http://www.neo-geo.com/ubb/smile.gif

HPMAN
12-05-2000, 03:03 PM
Well, tested some different EPROMS with same result...

Even when putting an original neo bios, I got the same result... (blocky green picture, screen flickering, game doesn't boot...)

It's very strange since the original bios works, and when switching to the other, the neo won't boot...

JMKurtz
12-05-2000, 04:25 PM
You're getting garbage when the original bios is in?

If so, you better look to make sure you don't have a broken trace.

Jeff

JMKurtz
12-05-2000, 04:26 PM
How about scanning the board so that we can take a look to see if there is anything obvious that is different.

Jeff

HPMAN
12-05-2000, 04:31 PM
Well, I use (your) double stack method with the original bios and ANOTHER original bios putted on top of it, and I got garbage with the top bios, not the bottom one...

Yeah, I can try to scan the board, but I'm not shure of the result.

By the way, how can I post a picture here ? http://www.neo-geo.com/ubb/redface.gif

Or else it's jmkurtz@macola.com, isn't it ?

JMKurtz
12-05-2000, 04:36 PM
Send the pic to jmkurtz@macola.com if you can't post it here... If everything is done right, you should have no problems, especially with two original bios chips.

Of course, the best solution, put in a ZIF socket.

Jeff

HPMAN
12-05-2000, 06:28 PM
Yeah, I sent you the pic...
There's a ZIF socket on the bios...