Just a small upgrade

Lots of things happening at work, so it’s good to do a little meditation by soldering in the evening. Guillaume sent me a Greaseweazle kit but the STM32 still looks like the next level of soldering to me. It makes 0805 components look large. I’m missing a 74F257 that was lost in the mail, so the 060 adapter has to wait for a while. But there are other ways to treat an A3640 rev 3.1.

First, a socket for the oscillator will make it easier to test a little overclocking.

The 68040@25MHz worked nicely with a 60MHz oscillator, pushing it up to 30MHz.

Since the A3640 provides the clock for the Amiga mainboard, the chipset and memory will get a tad faster, too. This hack is super easy and will cost you 2 bucks for a socket and an oscillator.

The next and a little more involved one is an upgrade of the v3.1 card to v3.2. Gladly this is a simple GAL update, but unfortunately the GALs are not socketed. This leads to a brief intermezzo with my favorite tool ever, the hot air rework station.

The kapton tape job was a bit sloppy and over eager

I had left the temperature at 245 degrees C from a previous experiment. Not good enough to take the part off. Let’s up it to 275 Celsius again (530 F) and the GAL slides off smoothly.

Be careful, this process does not need any force whatsoever. If the pads are slightly corroded or have been messed up before, they might lift off if you’re not careful. That makes for tedious repairs, don’t do it.

Phew, all went well. Let’s clean up

Cleaning up the pads with solder wick and isopropyl alcohol is essential before working on them again. Small unevenness can rip the pads off when cleaning.

I got a cheap adapter off eBay

The Conitec Galep 5 is a beautiful device to program everything from GALs to EPROMs to microcontrollers. I’m glad I still have mine from the beginning of coreboot times, but a TL866 is a more cost sensitive solution.

The best way to put the GAL back is with hot air

I’m using low melting point solder paste and the hot air rework station to put the GAL back on. I’m not happy with the 28 pin sockets I have, so I don’t bother putting one on.

With a little more time I can also apply the speedgeek Wait State mod, but that will require reprogramming another five unsocketed chips.

For now this is the end result:

And it still works and is stable:

Recap of a revised recap

When I got my A4000 late last year, I could not have been a happier kid. I fleas surprised to get it for a fabulous price and it arrived just in time before the holidays.

The A3640 was a good first victim. Notice the through hole caps that ripped off the pads

That joy lasted until I noticed that there was no mouse, a Super Buster r6 (WTH) and a semiprofessionally done replacement of all the capacitors on the board. Unfortunately through hole caps were used in the recap process.

You will find enough discussion about this on the internet, and people will suggest all sorts of craziness, like twisting off old caps or putting through hole caps on SMD pads. These are all terrible ideas. Don’t do it. If you have an Amiga (or any 30yr old computer), do it right or pay somebody to do it right. Recap services are not expensive and are definitely worth it.

One of the tricky parts is that the silk screen on the A3640 is incorrectly showing the direction of three capacitors. Make sure to consult the schematics.

Ruined! It is ruined! Or is it?

When I reached out to the southern California Amiga repair wizard Acill (Paul Rezendes), he suggested that I check out this video on repairing pads. I had to watch the whole thing twice, because it’s mind blowing. But hey, nothing that can’t be done, so here we go

This one is even worse. The pads are gone and the vias look corroded.
Got some copper foil in the mail, 1.4mil

It took me a while to get these right. I bought a cheap scalpel on Amazon
A cheap microscope is worth gold

To glue the pads on I used 2 component epoxy overcoat and let it dry over night.

It’s really tricky to keep this orderly awhile trying to connect the vias to the pads.

I spent a lot of time with my multimeter and the A3640 schematics, measuring the continuity of the pads

But the end result is pretty solid.
And we are online.

This one is certainly not winning a beauty contest. But for a first attempt in fixing a botched recap, I am proud to say that the card is now better than before I touched it.

Time to build a 68040 to 68060 adapter next!?