Falcon doesn't initialize blank screen

[sdisla]

Besides your suggestion above do you think at this point is worth to replace them?

See below pictures, this is what I can get with my scope.
CH1 ROM4
CH2 ROM3

Also, I noticed the screen characters looks improved even is just garbage hence U62 is not plug.
Lastly, I can hear a crack noise on the speaker once the reset button is press.
Observations are all new after U62 is not in the picture.

Thank you for your assistance.[/b]

Well that's good (despite the terrible sample rate on your scope! I assume you sampled at long baseline then zoomed in?).

Perhaps you can get something out of the diagnositc cartridge now.

If you have a source for a replacement GAL I would say it's probably worth trying it now. You've shown code is being executed if you're able to get the ROM4 line to activate. Very good.

My only slight hesitation in blaming that GAL immediately for everything is that it's not directly connected to any address lines that I can see and I'm struggling to work out how it may be causing the problems you've seen -- perhaps it's dragging one of the SIZE lines down to zero?

Anyway, I believe the GAL equations are on dev-docs.org and it should be possbile to make a new one.

BW

@Badwolf

This is correct, I will try to get ROM4 probe again on a different scope just to see if I can see these 7 pulses. Back to the GAL let me check if I can get a few blank ones and try to burn one. Diagnostic cartridge doesn’t work yet.

Thank you.

[frank.lukas]

The sources are in my archive too but I don't know if they work ...?

F030_GALs.zip

(9.8 KiB) Downloaded 45 times

[Badwolf]

@Badwolf
This is correct, I will try to get ROM4 probe again on a different scope just to see if I can see these 7 pulses.

No need. Two pulses is correct.

BW

[sdisla]

The sources are in my archive too but I don't know if they work ...?


F030_GALs.zip

Thank you!

[sdisla]

@Badwolf
This is correct, I will try to get ROM4 probe again on a different scope just to see if I can see these 7 pulses.

No need. Two pulses is correct.

BW

Got it.

[Badwolf]

If you're waiting for a GAL, don't forget that we had that problem with the top ROM data line. Worth re-running the data line test (all data lines alongside AS) for those first four cycles now?

BW

[sdisla]

If you're waiting for a GAL, don't forget that we had that problem with the top ROM data line. Worth re-running the data line test (all data lines alongside AS) for those first four cycles now?

BW

@Badwolf

I will check them in a few.

Just to make sure no U62 inserted.

I will repeat ROM (all data lines alongside AS) no RAM for easy access to the ROM pins with the scope probe?

Or is ok to check with RAM accessing them over the 30-pin connector?

Furthermore, has anyone ever tried to re program one of this GAL ICs?

Maybe it could be corrupted and re program (erase and write) sometimes can fix the problem if the IC is no bad.

Still waiting for blank ones and it will take a while.

Thank you.

[Badwolf]

If you're waiting for a GAL, don't forget that we had that problem with the top ROM data line. Worth re-running the data line test (all data lines alongside AS) for those first four cycles now?

BW

@Badwolf

I will check them in a few.

You can probably safely use the expansion connector (or the cart slot) this time. Remember we were expecting 602E for the first read (one AS cycle low), but were getting E02E.

BW

[sdisla]

@Badwolf

I will check them in a few.

You can probably safely use the expansion connector (or the cart slot) this time. Remember we were expecting 602E for the first read (one AS cycle low), but were getting E02E.

BW

@Badwolf

Data lines alongside AS

My interpretation:

D0 1000
D1 1100
D2 1110
D3 1100
D4 1000
D5 1101
D6 1001
D7 1001
D8 1000
D9 1000
D10 1010
D11 1000
D12 1000
D13 1100
D14 1100
D15 1000

Thank You

[Badwolf]

@Badwolf

Data lines alongside AS

My interpretation:

I think you need to work on interpreting these.

Remember, you're looking at the voltage at the end of the AS cycle (ie. the point it goes high).

I haven't gone through and done the analysis yet, but perhaps have another go and then try to convert them to hex. This will help you with debugging further if the GAL isn't the answer, so it's worth practicing.

BW

NB. There are nothing wrong with your images, it's just the translating them to binary I'm suggesting you try again.