Space Firebird Issues.

[conan]

Hi. Please can somebody give me some advice. Does this look like sync issues or graphics. I have got the boards from a blank screen to this and the game looks to be playing as the lines move around and then change colour and become static on the BEST 10 score page. I can almost see the ship warp up the screen in the demo mode too. But its all lines.
Any help would be appreciated.
Thanks

 

[DonkeyKongler]

does it play blind.........?

 

[conan]

I dont have any controls wired up yet. But its definately playing in demo mode.

 

[Lurch666]

Doesn't space firebird have a positive sync?

 

[conan]

Yes I was just reading that and with inverted RGB. That Happ Vision Pro is negative I think. Could that be the problem?

 

[conan]

Yes I was just reading that and with inverted RGB. That Happ Vision Pro is negative I think. Could that be the problem?

Just tested and its not sync

 

[philmurr]

Video needs to be inverted but -ve sync passes straight through

 

[Lurch666]

Do you have an oscilloscope you can use to show us the output of the sync pin of the PCB?

 

[conan]

Do you have an oscilloscope you can use to show us the output of the sync pin of the PCB?

Unfortunately not. Im thiniking of getting one but Im not there yet.

 

[Ronnie Dent]

It's handy having spare working boards to swap over and isolate the fault to either cpu or gpu board, where are you located?

 

[conan]

It's handy having spare working boards to swap over and isolate the fault to either cpu or gpu board, where are you located?

Im just outside of Harrogate, North Yorkshire.

 

[Ronnie Dent]

Im just outside of Harrogate, North Yorkshire.

Ah! far from Scotland lol, I know the chip sockets can be problematic! Worth a good look at those, these boards are known to be a pig to fix!

 

[conan]

What i am finding is that the chips just dissintegrate when you try and extract them and im proceeding carefully with a solder sucker and heat gun. They just fall apart.

 

[Lurch666]

Do you have the video GND from the monitor tied to GND? missing this can sometimes cause video issues.
Otherwise looking at the schematics the SYNC signals goes through a transistor (TR1) and some resistors so might be worth checking them.
The SYNC is generated by an LS55 at 1F. Have you checked that?

 

[conan]

Thanks for the help. Yes checked 1F LS55 and it comes up OK on my Xgpro I p[ulled it and scoketed it. I'll check TR1 and the resistors not looked at it yet tbf.

 

[conan]

Im suspicious its either both or one of the shift register MB455's, actually SN74198's in 6M & 5M (on video board) as I dont get much change having them plugged in or not. According to what I have read if I check pins 1 and 23 they should show activity and both of mine are held low. Pin 9 on 5H, 5I 7 6I (74LS174's) all show activity and they apparently send data to the 74198's. But Im really new to this so who knows. I have ordered some new chips so will wait and see.

 

[Lurch666]

No idea if pins 1 and 23 of the 74198s are supposed to be low but look for activity on the chips that feed those inputs.
There's the LS00 at 4M and another at 1D are fed from 1E and 3L.