Thank! 
As soon as I've solved the damn problem with the crossed serial cable (thanks again to Gary), I'll be able to start running the first scripts. If you like, and if you have time, I'll be happy to keep you updated (in addition, I'll be sure to seek your advice and suggestions).




(Southern Italy is a place that truly contains so much beauty layered over centuries of history)

Get a cheap heat sensor from aliexpress
It really helps with finding bad caps

Btw may that be issue with capacitors, exceptionally since i already trashed original psu because of this and this thing surely wasn't powered on for like 15 years minimum

Yes. Check for swollen (and possibly leaking) capacitors too.

"In the meantime, you can very closely inspect the mobo (top and bottom) looking for any signs
of overheating or other possible damage to the myriad of tiny electronic components and traces."

And now, before I really go to bed... while you're inside the thing, also please photograph the white
label on the mobo like this one below:



It looks like this one has a label pasted over a label. I've also another similar one to photograph here as well.

Btw may that be issue with capacitors, exceptionally since i already trashed original psu because of this and this thing surely wasn't powered on for like 15 years minimum

Searched your serial number @ https://appleserialnumberinfo.com/Desktop/index.php and came up with this:



Then searched same with EveryMac.com and it returned this info:

     

And for more detailed info on your MDD (like RAM specs, basic OS, etc.) check out:
https://everymac.com/systems/apple/powermac_g4/specs/powermac_g4_1.25_dp_mdd.html

And which RAM slot do you have the single 512 mb stick in? If it is not in J20, try also in other slots.
You might even try other RAM sticks in other slots, leaving the J20 slot empty. For more info see:
https://macos9lives.com/smforum/index.php?topic=7637.msg59231#msg59231

Or read that entire topic, beginning here:
https://macos9lives.com/smforum/index.php?topic=7637.msg59178#msg59178

Sure you might have a failing CPU or a damaged mobo but for the machine to only allow one stick of RAM,
well maybe you have the J20 slot problem too? If the single stick works in J21, J22 and J23, leave the J20
slot open and then test (one at a time) two other sticks along with the known working stick to see if it might
work with two or three sticks, total. (With the J20 slot left open.)

And maybe you’ve got mixed & matched RAM? PC2100 DDR and PC2700 DDR?

[I’m now going to bed!]

If you photograph the CPU, do please also photograph the entire open view of the mobo too.

AND I’ve sent you a PM. (In case you have not noticed it). Check “Messages” at top of opening page.

Cheers!

Quote from: aBc on September 20, 2025, 09:25:01 PM

The ONLY thing that I might even remotely question is the “3-4 users” estimate of those “heavily into gaming and or animation”. Thinking that there are far more gamers around here now than we might suspect.

Sorry… I meant the 3 or 4 into heavy animation using an MDD as we're discussing here. There are quite clearly a lot of vintage gamers playing with vintage Macs of all kinds.

My apologies Gary. Was just needling you a bit and I should have included a smiley there.
Actually referring to an excellent post by you, adding so much more insight to the topic.
Thanks!

I think you have arrived at the most likely conclusion.

The lesson here is that BU drives are sacred devices that should be labeled and securely stored unless/until you are absolutely certain you will never need anything they contain. If you reuse one, initialize it first.

I can afford any measures apart from replacing motherboard and daughterboard as in my country i am never finding replacement parts due to low amount of mdd sold there

Also when i replaced gpu with mx 2 400 with dead vram chip it had same symptoms apar from dvi thing

Tommorow i can remove paste and send pic of cpu