Space Firebird

[Adrian Purser]

I had a Space Firebird board that had a blank screen and had a sound effect constantly playing. The star field was only displayed when the board was held in reset.

The cpu seemed to be running so I put a logic analyser on the address bus to try and see how far it was getting. I ran the game in mame with the debugger and I was able to trace it to a point where it read the inputs. It did a test of the input "TEST TP-8" and if it was active then it jumped to code at address 0x3800. I could see by looking at the data bus that the real board was reading 0x40 from the port but mame was reading 0. I checked the output of the 74LS240 at 1L and it was stuck when the device was enabled, so it was probably the input of the chip at fault. I replaced the IC and the board sprang into life. The code was no longer jumping to 0x3800 and continued to boot into the game.

 

[mozie]

Well done, these boards seem to die often, I have one here at the moment that works fine but the shot sound is missing, all other sounds are present, any idea where to look?

 

[Ronnie Dent]

I too have piles of these boards with various faults from dead to bad graphics, I made a test rig to work on them but it's beyond me!

I did send them to a repairer but most came back with the same faults I sent them off with!

 

[Adrian Purser]

Well done, these boards seem to die often, I have one here at the moment that works fine but the shot sound is missing, all other sounds are present, any idea where to look?

This is the first time that I've worked on a space firebird and I didn't look at the sound board but I'll have a look at the schematics when I get 5 minutes.

 

[patzik]

I recently worked on 3 space firebird boards, biggest problem was the ram ic's, I ended up with 12 faulty ones in total and haven't found a good place for affordable replacements. i tried 5101 ic's but they are not fast enough. Anyhow I also had some sound problems which I fixed. I remember one of the boards had strange sound for fire, this ended up being a bad capacitor. The sound board has some LM324 amps, if sound is completely missing this is where I would look first. Also check the 555 timer, if I remember correctly this generates the vibration for the shooting sound.

 

[Macro]

Did you ever find a good substitute for the video ram chips ?

I think I'm going to need some ... (once I find some way to test them, trying a script on ABI 4000, but if that fails then I may just plug them into a galaxian PCB and use the Fluke on them)