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Old 14 November 2019, 10:33   #21
solarmon
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Many thanks for confirming what I was hoping was the case (I'm not fully across how ICs are built, but figured tolerances wouldn't be THAT particular). Either way, I can't see how the CIA could cause a green screen as it isn't involved in the POST memory check sequence.

Cheers,

Tom
Well, in another thread (A500 memory issues), but for an A500, the Odd CIA was put in backwards and that caused the system not to boot...
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Old 14 November 2019, 11:30   #22
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Hmmmm. Food for thought! Though checking... the CIA is both the right way around, and never been de-soldered (the SMD solder is still pristine). Won't discount it though...
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Old 14 November 2019, 12:06   #23
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Hmmmm. Food for thought! Though checking... the CIA is both the right way around, and never been de-soldered (the SMD solder is still pristine). Won't discount it though...
I just meant that I would not expect for a CIA to be put the wrong way - effectively not powered and 'not there' - and still stop the Amiga from booting. I don't understand exactly why that scenario would be an issue.
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Old 14 November 2019, 12:55   #24
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In the case of the A500, the green screen was being caused by a power fluctuation on the 5V rail, although a multimeter showed 5V, the oscilloscope showed the 5V was actually oscillating rapidly between 3.3 and 5.3V which prevented the RAM from initializing properly. Replacing the caps on the 5V rail sorted that out and got rid of the green screen. The CIA backwards caused it's own problems
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Old 15 November 2019, 10:57   #25
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In the case of the A500, the green screen was being caused by a power fluctuation on the 5V rail, although a multimeter showed 5V, the oscilloscope showed the 5V was actually oscillating rapidly between 3.3 and 5.3V which prevented the RAM from initializing properly. Replacing the caps on the 5V rail sorted that out and got rid of the green screen. The CIA backwards caused it's own problems
Ahah. So I am getting a lower than expected reading on the 5V feed - 4.8V. I would have expected removing the caps to get around any erratic feed issue however... maybe not so?

I do have fresh caps, maybe I’ll pop them on and see?!?
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Old 15 November 2019, 11:17   #26
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Ahah. So I am getting a lower than expected reading on the 5V feed - 4.8V. I would have expected removing the caps to get around any erratic feed issue however... maybe not so?

I do have fresh caps, maybe I’ll pop them on and see?!?
4.8V is fine/acceptable if it is stable. The issue with Vypr's A500 was that it was fluctuating, and going out of acceptable limits.

But a re-cap is good overall, especially if you have the caps already.
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Old 16 November 2019, 14:14   #27
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Well, the recap didn't fix it... but I *did* find a dud trace coming out from C321 whilst working on it. Was hoping this would fix the issue but: Nope. It's no doubt fixed something, so hopefully once I get to the bottom of this green screen, the thing will work a treat.

Just gotta wait for the DiagROM now I guess...

Cheers,

Tom
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