GBA1000 rev4 Build Log

[storhemulen]

RGB via the 23-pin D do you mean? (Rather than the flicker fixer 8-pin DIN to VGA)

Precisely!

 

[storhemulen]

Starting to make a little progress with my build. Most of the "core" components are there, including almost all the "bird feed". Tried turning it on, but no luck yet, only a black screen.

Does anyone know if the FastRAM is necessary to get to the Kickstart image? Also, I have not programmed IC53-IC56 (GAL20V8-15) since they haven't arrived yet. The only GAL I have on the board right now is IC14.
All custom chips except Agnus have been tested in a working A500. Also, the CPU was tested working in a DKB Mongoose and the 28 MHz osc have also been tested successfully. The homebrew video hybrid works in the A500.
IC57 (ispLSI1024) was purchased programmed from piacc64 and has been tested by him.

So, any ideas on how to proceed or should I just be flogged for severe incompetence?

 

[cpiace64]

verify all jumper

i suppose need amber for video output

 

[storhemulen]

If I use the RGB output for video I won't need amber installed, right? I will check jumpers again.

 

[ajk]

Yep, Amber is not necessary for the native 15kHz video.

 

[Ordyne]

You will need the fast ram otherwise you will get a yellow screen IIRR



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[storhemulen]

Thanks Ordyne! Since my screen is black there must be something else wrong also. I would like to see something on the screen before I proceed with soldering the fast ram chips, if only just a colored screen.

I connected the keyboard and hit the caps lock key several times and the caps lock LED went on and off a couple of times until it froze. From what I gather, this means that after the keyboard RAM buffer is full the LED freezes since the CPU is not operating. Maybe I should check if there is a good clock signal fed to the CPU.

 

[Ordyne]

I'm only going from a vague memory but isn't there a few gals at the side of the lsi1024 that you have unpopulated?


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[storhemulen]

Correct. None of those GALs are mounted yet. It could be they are necessary to get a picture at all, I can't really tell. Hopefully I'll get those chips soon and program them.

 

[Ordyne]

Going from what I remember trying to fault find a friends GBA your going to need those GALs. On holiday with no schematics or I would try to be more help!


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[bootsie]

I'm having problems getting a decent picture from my flicker fixer - I've put up a thread https://www.amibay.com/showthread.php?86683-GBA1000-Flicker-Fixer-problem but so far no responses.

Is there anyone based in the UK who has a working GBA1000 flicker fixer and could test my Amber and DIN8->VGA adapter cable if I posted it to them? (or even better if you're somewhere close to NN13).

Please let me know if you can help.

 

[Ordyne]

If you're stuck I could do it


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[bootsie]

If you're stuck I could do it

Yes, I am a bit! I'll drop you a PM.

 

[bootsie]

Thanks to Ordyne for testing my Amber, Hybrids and cable. All working fine now.

 

[Ordyne]

No problem, what was it in the end?


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[bootsie]

Apparently nothing! Plugged it all back in, worked first time.
I guess something not seated properly.

 

[storhemulen]

Success! After finally getting some GAL20V8's and some time to program them, my GBA1000 works!
Will try to boot WB next and run some tests. Only chipmem installed yet, which I scavenged from a SIMM module.

Also, recapped the old A1000 PSU for good measure.

 

[storhemulen]

Does anyone know how much FastRAM must be installed to be detected? Would one "row" or one "column" of the 4x4 matrix do (i.e. 2MB)? Or must all of the 16 CY7C1049 be installed?
I would rather get a smaller amount working at a time.

 

[storhemulen]

A bit stuck again and could use some advice. All the FastRAM chips are soldered but no "other memory" is detected after booting WB2.0 from floppy (kickstart 3.1 installed).

Here's what I've done so far:

- Checked for shorts between pins of SRAM
- Checked that all pins are in contact with their pads
- IC53 programmed with IC53_15ns.jed or IC53_01_15ns.jed (both boot, but no fastram detected)
- Tried with both 40 and 50 MHz oscillator
- Early startup does not show any expansions

Please help me someone!

 

[bootsie]

Just a wild guess, but have you tried changing the position of jumper S5? I seem to remember having to fiddle with S5 and S7 to get my Fast RAM working, but that might have just been a 24-bit/32-bit mode thing.