I’ve heard of the whole Chinese relabeling industry, but in the past I have always been lucky with my eBay purchases. Until this last time.
I kept ordering a number of times from the same folks on eBay, but it seems that they ran out of genuine AMD 27C400-120s and decided to ship relabeled Toshiba -150 parts instead.
The large window of the flash parts that were actually delivered was immediately making me suspicious though, and luckily my GERMANY made fiber glass scratching pen found a good use as a detective in this case.
A few light rubs over the inscription reveals the Toshiba TC574200-150 nature of it all. Reached out to the seller for a refund.
Well actually it wasn’t escape that was broken on my nice click-a-dee-clack Amiga 4000 keyboard, but CAPS LOCK! And bit even the key itself, it was the LED that just wouldn’t show the status. No problem, let’s take it apart
At first I thought the LED might have died after my recent diode intermezzo on the Amiga board. But measuring with my multimeter I see that the LED is just not getting any power. Let’s look at the membrane.
There was a piece of the trace missing. It seems it had corroded away. The previous owner probably spilled Coke on it. My first approach was to scratch the green cover of the existing trace so I can connect to it.
Then I covered it with some of my copper foil. I wasn’t expecting it to work, really, but it was worth a try because I didn’t have a conductive pen, and certainly soldering is not an option, unless you want to buy a new membrane (these are the same as the A500 membranes and are available). But my better half is trying to make me frugal, and we the people are creating too much e-waste anyways. So I ordered a nickel conductive pen on Amazon. It arrived today.
I connected the two distinct pieces of the trace to each other with the pen, and after the ink dried, covered it with a piece of copper foil again, for no other reason than that it is shiny. Aaaaand……:
Putting the while thing together again.
While testing, I’m actually not using the keyboard on the Amiga, but in my PC with a little adapter that I built with a cheap Arduino Pro Micro clone and tkoecker’s amigakb.
I ordered the boards through PCBWay and they’re super easy to solder. I have 9 more, because I didn’t want to pay more for shipping than the PCBs. So if you want one, drop me a note.
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.
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.
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.
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.
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.
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.
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.
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.
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
To glue the pads on I used 2 component epoxy overcoat and let it dry over night.
I spent a lot of time with my multimeter and the A3640 schematics, measuring the continuity of the pads
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.