Trying to fix Mikro's wrecked TT board

[dml]

Excellent progress, Doug! Glad to see my poor PCB alive and kicking!

:D

The reflow attempt was just some rune-casting as I was out of ideas for the day and I didn't see anything really wrong with it except looking a bit dull and crusty brown stuff around the caps, which might have just been old flux. But suspiciously, only in that area at the front, nowhere else.

It was only when I realised the solder refused to melt and flux wasn't really helping - there was a problem worth digging into. Maybe a battery leaked nearby and just got to it? A ranged attack from a dying PC :p

[dml]

Didn't take a pic before, but here's after. The PGA pins were partly reflowed but the caps I didn't touch yet. A few of the reflowed pins wouldn't stick to the thru-holes and just separated completely, took a few passes to join them to the board again.

The solder at those caps is corroded to the point it crumbles instead of melting - they look not too bad here because i already scrubbed the area with IPA but there was grey/white and yellow stuff around each pad. A few rows back and the solder joints seem ok. There may have been a chemical source (or leaky battery) nearby where it was stored.


Anyway, time to think about an upper shell on this thing and then onto other problems - like puzzling out how to fit the memory board on top of that CPU board with the VME ribbon cables in between.

crusty.jpg

[dml]

To avoid starting a new and very short lived thread, adding this here...

This is another machine I had to work on - Falcon with a dead COMBEL (& dead GAL, dead DAC - somehow VIDEL survived), lifted pads and torn tracks under the COMBEL, damage to the PCB upper layers exposing inner layer in a couple of places, some other related problems... This one very nearly didn't come back, narrowly escaped a parts bin.

combel-rework.jpg

[exxos]

So when can I send my Milan to be fixed :P

[dml]

So when can I send my Milan to be fixed :P

You have a dead Milan? :hide:

[exxos]

You have a dead Milan? :hide:

Yep :(. Previous owner had it working fine, then he dropped a screwdriver somewhere on it and its never worked since. I changed a broken simm socket, and fitted the wrong angled one, then that's as far as it went. Just never have time to look at the thing :( I pretty much assume one of the PLDs is dead :( I think the files are available online I just need to get around to testing the chips :roll: I think I tried a different CPU, but it was like 20 years ago now :lol: :roll:

I'm going to send some graphics cards to @PhilC at some point soon, pretty sure 2 of them work but they all mixed up now. No use trying to troubleshoot a system if there's no working graphics card :P would be great to get it up and running again but as always, too many projects are not enough time...

IMG_3388.JPG

[dml]

Jokes aside :hide: I don't mind taking a look at it as a slow burn background thing (which is the case for all of my repair attempts usually) - if it's a physical fault or anything but the PLDs I might find it. But would need a way to confirm life without a video card (I don't know anything about Milan machines really). I have some ISA video cards here but no idea if any would work in that thing so a lot of guessing involved. If it reports to serial at boot, that might be enough.

If one of the PLDs is gone - not much I could do though :) even if to replace the chip, I don't know that I could re-flash it.

Are there even schematics for Milan?

[alexh]

The PLX PCI switch bridge in the middle was *designed here*. Long before my time.

[exxos]

....
If one of the PLDs is gone - not much I could do though :) even if to replace the chip, I don't know that I could re-flash it.

Are there even schematics for Milan?

Looks so on https://docs.dev-docs.org/

Some other bits on the Milan site also

https://www.uweschneider.de/en/downloads.php

Milan_040_Schematic.pdf

Yeah, verifying the PLD is even working will be the first step , but I don't believe the files wherever released, so its a bit of a nonstarter really :(

I think finding suitable replacement chips will be a pain, but I would probably just send the board off to a professional fab house to swap them all out anyway.

I was talking to Uwe briefly about it years ago because I was asking if he could take a look at it he didn't respond to the question. I guess I could ask if the files were released somewhere..


:threadjacked:

[dml]

The PLX PCI switch in the middle was *designed here*. Long before my time.

Oh - does it happen to be the same PLX IC used on the CTPCI?

[EDIT]

...ok apparently not quite the same IC. PCI9080 vs PCI9054