NEO AES palette RAM problem.

[omnedon]

I'm trying to bring back a green screening NEO AES board here (old style).

Green screen is palette ram, of course. The system does not have a UNI BIOS installed, but if it was likely worth the effort for troubleshooting I'd consider trying it.

Anyway, what I've already done is this:

Checked all pallette ram traces (Thanks to the Master JMKurtz with identification and location of the correct IC's). No broken traces.

Removed both palette ram chips (broke no traces) and installed sockets.

Pulled two known good palette ram IC's (same type) from a donor board. Popped them in the sockets. More green screen fun. Tried a couple IC combinations, even though the replacements were known to be tested and good. No go.

I've been over *everything that leads to and from these IC's with my magnifying glass. Nothing. No broken traces, no burns, nothing. Any ideas on what I should check next, before this board goes nto the donor pile?

I could install a BIOS socket, and pop one of raz's magic Uni BIOS 2.1's in there. Is it possible that that would give me more info? What sort of info could it give me? Could anyone help me interpret it? I get lost in memory addresses and hexidecimal numbers.

 

[DokToR]

did you take a look in your socket cartridge ? if any are missing or broken

 

[Razoola]

A unibios 2.1 will give you more information (like what you would see on a MVS). Note that the tests are done differently with a unibios though (don't simply power on with no game in).

To do the test with the unibios 2.1 simply power on the system with a game in while keeping buttons A+B+D held down. All going well you will see a screen with the actual error on it (ram location etc). This is of course providing that at least some of the palette RAM works enough to be able to set different colors to make the text visable.

Basically the unibios hardware test on AES will keep looping until you release the button code (if there is no error). Each time it loops the screen will flash white.

Its quite possible the actual problem with the AES is with the palette ram bank switch, maybe one bank works but the other bank dosent due to the switch not correctly working.

Raz