Fixing a ZZ9000 - Trace cutting

I am the proud owner of a Vintage Amiga 3000 that I rebuilt/fixed recently, on which I added a wonderful mnt ZZ9000 add-on card that provides USB, Ethernet and RTG graphics, and who-knows-what since the card is highly customizable thanks to its FPGA + dual core arm processor addressable from the Amiga side.

All was well until I got a mail describing a bug on the pcb. A trace is sending 3.3V into a 1.8V line into the FPGA card. Can't blame MNT, the design was checked and documentation not clear about that pin.

This is causing overheating of the FPGA, and of course is plain bad ...

So there are two options to correct the issue : either drill a hole through the PCB, or cut a trace near the connector between the card that plugs in the amiga and the FPGA daughter card.

I chose to cut the trace, I fortunately have good eyesight :-)

Get the tools

So I happened to have this set of scalpel like cutters. Never thought I'd use them to fix a computer :-) . It worked perfectly well ...

Preparing the card & identifying where to cut

Here is the normal ZZ900 card with FPGA plugged-in :

Remove the FPGA daughter board :

You will have to cut there :

Cut trace next to 24th pin from the left, lower row, U12 :

Cut !!

Should get you something like that (just after cutting, still not cleaned) :

Checking that it worked

Now that you feel like a hardware butcher, check that it worked ...

get a multimeter in continuity mode
put the FPGA daughter card back in place
check continuity between C53 lower pin and C55 lower pin
you should get NO continuity anymore !!

Did it work ? Wanna be sure ? Check on your machine !

Confirmation via the machine itself

MNT got the ZZtop tool out ! Best name for a tool in a while ! This tool will allow you to get the FPGA temperature and voltages, so you'll be able to confirm it worked

In order to run ZZtop, you need to upgrade your firmware to 1.7b2 . Drivers 1.6 work fine with that firmware.

On my machine (open case), before doing the cut, after ~20 minutes of usage I used to have :

More than 75° Celsius, and 3V Aux voltage.

Now, after 2 hours uptime :

Around 14° Celsius less ! Not bad, and you can see the correct 1.8V now ! Success !! ... Gimme All Your Loving ... (I have had this song in loop in my mind for the last 20 minutes, thanks MNT !)