Amiga 1200 - Looking for some help

Tandrews-ny · 02 March 2021, 05:38

Hello fellow Amigans!

I have a customer's 1200 that I could use some guidance on troubleshooting.

Here is what I know:
Using diagrom, nothing coming through on console
Tried using an accelerator, no change.
I have video sync
Reset is high as it should be
Have 14mhz clock
ROMs are being read for a short period, then activity stops
No CPU halt, but even no roms results in no HALT
I have followed the initial steps of Gayle with another tech and we're seeing activity.
We're seeing RAS and CAS signals. Seeing RGA signals.

What I can't figure out, is why the system just kind of stops. I'm looking for "next steps". Any guidance would be appreciated.

Hopefully I answered any primary questions.

Tandrews-ny · 03 March 2021, 17:11

Solved on my own. Looking at CCK on other chips outside alice, I found it was trash. Traced the circuit to a 27 ohm resistor and found it was reading 11Mohm. Replaced it with a 22ohm (close enough right?)...booted right up to diagrom. System boots kickstart now too.

02 March 2021, 05:38	#1
Tandrews-ny Registered User Join Date: Feb 2020 Location: Rochester Posts: 44	Amiga 1200 - Looking for some help Hello fellow Amigans! I have a customer's 1200 that I could use some guidance on troubleshooting. Here is what I know: Using diagrom, nothing coming through on console Tried using an accelerator, no change. I have video sync Reset is high as it should be Have 14mhz clock ROMs are being read for a short period, then activity stops No CPU halt, but even no roms results in no HALT I have followed the initial steps of Gayle with another tech and we're seeing activity. We're seeing RAS and CAS signals. Seeing RGA signals. What I can't figure out, is why the system just kind of stops. I'm looking for "next steps". Any guidance would be appreciated. Hopefully I answered any primary questions.

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03 March 2021, 17:11	#2
Tandrews-ny Registered User Join Date: Feb 2020 Location: Rochester Posts: 44	Solved on my own. Looking at CCK on other chips outside alice, I found it was trash. Traced the circuit to a 27 ohm resistor and found it was reading 11Mohm. Replaced it with a 22ohm (close enough right?)...booted right up to diagrom. System boots kickstart now too.

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