exxos's Atari, Amiga & retro forum

amigaricc wrote: 29 Mar 2025 14:51 Does Diagrom need any 74 Logics to run? For example U103 or U540 /U541

Nope. It needs U303 to be not asserting BGACK (i.e. it should be high). Thats all i think. It doesnt need most of the chipset. It just needs ROMEN low at boot.

ROMEN at U500 (12) is oscillating as well as on Gary (21).
Can I put ROMEN low by shortening it to ground so we can get some kind of output on serial console. (did that and there is some garbled output on serial for a bit and then it repeats)

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this is what is displayed on serial when shortening ROMEN to ground

amigaricc wrote: 29 Mar 2025 14:08 OVL Line form CIA (2) to Gary (30) tested fine

I do not want to "butt" in but:
Did you actually test the CIA and the OVL pin?
Did you swap the CIA's?
Did you measure what the OVL line does during startup or after a reset?

Are you using the original PSU?
Can you send us a high res picture of the PCB?, especially near the CPU?

Maximilian wrote: 29 Mar 2025 17:33

amigaricc wrote: 29 Mar 2025 14:08 OVL Line form CIA (2) to Gary (30) tested fine

I do not want to "butt" in but:
Did you actually test the CIA and the OVL pin?
Did you swap the CIA's?
Did you measure what the OVL line does during startup or after a reset?

Are you using the original PSU?
Can you send us a high res picture of the PCB?, especially near the CPU?

You do not butt in any help is welcomed.

I tested both CIA's on a rev 6.4 Board and they are fine
I did test Pins and sockets for OVL Line and they are fine.
Tested board with 2 different PSU's and same behavior.

I disconnected all the Data and Address lines on the CPU in hopes to get some kind of output on the serial connection but nothing.

amigaricc wrote: 29 Mar 2025 18:34 I disconnected all the Data and Address lines on the CPU in hopes to get some kind of output on the serial connection but nothing.20250329_133218[1].jpg

I dont follow this logic. The CPU needs to actually address the serial port and send it data. Without data and address lines nothing will happen in the system.

Was checking if the CPU would come out of HLT state

amigaricc wrote: 30 Mar 2025 02:34 Was checking if the CPU would come out of HLT state

"When the processor has stopped executing instructions (in the case of a double bus
fault condition, for example), the HALT line is driven by the processor to indicate the
condition to external devices."

So it would need to be executing garbage instructions for a bit to hit that

That looks like a nice board!

Again, are you using an original A2000 PSU?
You checked all voltages (different chips) and clocks?
You can use an A500 repair manual for this for reference.
Did you check the PCB for scratches or any other damage?
You have no addons installed?

What do the address and data pins do after reset?(check multiple times)
Do you have a high/low setting on your multimeter?