Thursday, December 10, 2015

Is It Broken? Try Leaving It On

Recently, I’ve acquired a bunch of vintage computer hardware from various sources, whether donated to me personally or stumbled upon during scavenger hunts through crazy places that used to be companies whose owners have pretty much turned into hoarders.  It’s been quite a tedious process getting some of these things working, but surprisingly, there have been very few instances lately where my skills with a soldering iron or my cache of loose parts has actually come in handy to fix something.  In fact, most things have come back to life surprisingly by simply plugging them in and giving them some time.

Cases 1 & 2: Some Commodore 64 Computers


Last week, a kind fellow who was moving granted me three Commodore 64 computers belonging to him and his brothers.  They grew up with these machines, and had a large collection of games and utilities on floppy disk.  There were also accessories such as floppy disk drives, joysticks, plenty of power supplies & A/V cables, printers, and some original documentation.  On the first night I had them, I tested all three.  One wouldn’t even load BASIC.  The other two loaded BASIC just fine, but the keyboards were all messed up and I couldn’t type anything.  I assumed they needed to be cleaned, but went on to do something else that night before going to bed.

In following up with these machines the next day, I realized I’d left one of them plugged in overnight.  I would imagine it’s wise not to leave something plugged in that you don’t necessarily trust to be in good shape, but since I was still alive and the house hadn’t burned down, I tried turning it on.  Lo and behold, the keyboard worked flawlessly!  However, the second machine still exhibited many problems with its keyboard.  One most amusing issue was upon pressing the special Commodore “C” key, the text on screen would quickly oscillate between uppercase and lowercase, thus it was apparently random what case the letters would be in once you let up on the key.  I had an inkling of how to treat this one, and so the experiment commenced.

Sure enough, after the second Commodore 64 (a 64c to be specific) had been plugged in for some time, its keyboard also started working perfectly.  Without much effort at all, I suddenly had two working Commodore machines.  (The third one must have a more substantial problem; it never came back to life.)

In the end, I kept one of them (a standard 64 with a switch to choose between regular Commodore BASIC & JiffyDOS), and gave the other two away to members of the local Vintage Computer Club (these machines were a regular 64 and the 64c) along with some of the accessories.  (It’s good karma to give stuff to the Computer Club for free, because perhaps they’ll consider you later if you ask them for something.)

Case 3: An Amiga 500


Last month or so, the Computer Club was offered an Amiga 500 and a number of accessories and disks by someone looking to part with it.  I was the first one to respond to the listing, and also the pickup location was fairly convenient to my office, so it fell into my hands quite easily.  Never having really seen an Amiga prior to that point, I spent a while musing over the hardware and physical characteristics, not to mention trying to find a proper 23-pin RGB cable, before attempting to do anything with it.  (I finally gave up on the cable and am simply using a composite cable for a B&W picture at the time of this writing.)

To do anything with a stock Amiga 500, the chip that stores the initial program (the Kickstart) insists that you insert the Amiga Workbench OS disk.  After finding such a disk in the donated stash, I inserted it and BOOM, the whole system just shuts off.  This became a repeatable & invariant event, so I tried several other floppy drives in the system to no avail.  I even started to pick out floppy drives with long Eject buttons so that I might be able to poke them with the case on (the Eject button can’t be reached by hand on a standard drive if you just randomly put one in the case since it sits pretty far back).  After attempting and failing to modify a PC’s floppy disk drive to work on the Amiga (you have to modify the outputs of Pin 2 & 34 on the bus), and finding that the long-button drives I picked actually had the buttons in the wrong spot (dremel time, then, perhaps?) I took a step back and put the original drive in the system.

Mind you, I had just also cleaned the system with a can of compressed air, plus replaced the electrolytic capacitors that weren’t already Nichicon brand, but I don’t think the recapping actually helped anything.  Honestly, it was probably the light cleaning I did — even still, absolutely nothing technical went into restoring the system back to working order.

Actually, that’s a bit of a lie: the previous owner had, a long time ago, replaced the stock processor with a Motorola 68000 and modified the clock speed to run at 14MHz.  Since some of the wires had become brittle over time and had fallen out of place, I got to hunt for documentation as to how this modification worked and how to rebuild it for myself.  It required poring over really old forums and message boards and downloading files whose formats are foreign to modern computers anymore, but eventually I got the information I needed.  It is now happily running Amiga Workbench 1.3.2.

Yay, at last, it loads Workbench!  Now if only I could Retr0bright this whole picture... :-P

On the Flip Side…


The one project of mine that’s actually gotten worse over time is the IBM 5150.  The keyboard port must need cleaning, since with any of the keyboards I have that are compatible, it only ever outputs gibberish anymore.  I also attempted to use its floppy disk drives for the first time in probably 20 years, after having purchased a floppy disk controller (and then found two more for free shortly thereafter).  The drives are in poor shape, despite having cleaned the heads with a Q-tip and 99% isopropyl alcohol.  It is likely that the belts need replacement too, and possible that it needs to be recalibrated (which should be a lot of “fun”…)  One of the drives had its closing mechanism fall apart because it couldn’t hang onto the little plastic rice-like “bolts” that keep the mechanism together.  I’ll probably need to cast or 3D-print new ones, since they must be worn down to the point where they no longer fit properly.

I also found a 5151 MDA monitor (Monochrome Display Adapter) and an MDA adapter card.  Unfortunately, either that monitor or the controller doesn’t work, because I don’t get a picture.  I suspect it’s the monitor because the computer would (should?) emit unusual beep codes if the card were faulty.


[Edit 12/12] As a follow-up, after leaving the IBM 5150 & 5151 plugged in for a couple days (the 5151 has a special power plug that plugs into the 5150 power supply), sure enough, now that monitor works too!  I fiddled with the brightness & contrast knobs after seeing a green trail of "ooze" after turning it off when attempting to test it.  You know (or maybe you've forgotten) the remnants of the video signal left on the monitor in the brief flash of time when the electron gun finds its resting position and powers down.  That little green flash indicated it was doing something, and so after playing with the knobs, I now have a working green-screen monitor.


Yes it works now, but that doesn't fix the burn-in... :-(  But hey, can't really complain when it cost $0!