Dmitry Brant – Dmitry Brant

Brain dump, October 2024

Macintosh PowerBook 100

Restored another vintage laptop! This time, the patient is a Macintosh PowerBook 100, which came from a dear friend of mine who allowed me to restore it after recovering the data from its hard drive. The PowerBook 100 was clearly intended to be a “lower-end” model (even though it still had a price tag of $2,500 when it was launched in 1991), with a very minimal design, cheaper-feeling plastic, small monochrome 640×400 LCD display, and no built-in floppy drive. The upshot is that the inexpensive no-nonsense construction allowed for a fairly easy restoration!

When I attempted to power up the laptop as-is, it just made a few crackling noises through the speaker, and not much else. Otherwise it appeared dead. Time to open it up!

The top and bottom halves of the plastic casing are held together by three screws (!), and once these are removed, the entire thing pops open effortlessly.

Looking closely at the humble motherboard, I see the potential culprit right away: failed capacitors that have leaked and corroded. Hopefully the extent of the corrosion is minimal and didn’t affect any of the chips or other components besides the capacitors themselves. I’m hoping this could be as easy as re-capping the board, i.e. replacing the capacitors.

I proceeded to remove all the capacitors that had the slightest indication of corrosion, that is, any capacitor whose solder joints didn’t look totally pristine and shiny. And after removing each one, I cleaned the surface of any residue with alcohol, and then installed a new capacitor with the same value. In all, I replaced 10 bad caps, all of which were a small surface-mount variety, and were either 10µF/16V or 1µF/50V. My new caps are a bit longer than the old ones, so I oriented them horizontally on the board:

And, after reconnecting the display and keyboard back onto the motherboard, let’s try applying power again:

Hey presto, it’s alive!
A bit more cleaning of dust under the keyboard, removing the gunk from inside the trackball mechanism, and a general wipe-down of the exterior, and we’re ready to reassemble!

And there we have it, a lovingly restored PowerBook 100, with 2 MB of RAM, running System 7.0.1. The only unusual thing about it is the hard drive, which is a whopping 1 GB! This was clearly an upgrade from whatever hard drive it had originally (probably something like 40 MB), which must have been installed many years after it was purchased. This implies that the user of this laptop got quite a lot of mileage out of it, probably well into the late 1990s or even 2000s, which makes me happy.

Finally, to round out this restoration, let’s remove this hard drive and replace it with a CompactFlash card, preloaded with tons of vintage games and apps for the Macintosh.

The hard drive interface on the laptop is technically SCSI, so the original hard drive must have been a SCSI drive. The newer 1GB drive is an IDE drive, and came with an adapter board that fits underneath the drive, which translates between SCSI and IDE. This is quite convenient, since we can now plug in a cheap IDE-to-CF adapter, with a generously large CF card that will become our new hard drive. At last, let the retro gaming commence.

MC-3020-Extra tapes!

Recovered data from several MC-3020-Extra and QIC-3020 tapes. These “Extra” tapes have the same front-facing “interface” as their smaller QIC-3020 cousin, except these are larger length-wise, allowing for larger spools inside the cartridge, and therefore a higher data capacity. Of course these cartridges have the same fatal flaw as all other QIC tapes, which is the flimsy tension belt inside the cartridge that drives the motion of the spools. This belt is virtually guaranteed to fail over a long enough time, and since these “Extra” cartridges have even more moving parts inside, they are even more prone to failure.

This batch of tapes was in particularly rough shape: the tension belt in each tape was broken, and was also adhered to the surface of the tape medium. This was likely because the tapes were stored under excessive heat or humidity, which will cause the belt to break down and react with the tape itself. This required pretty extensive cleaning of all the gunk and pieces of belt that were stuck onto the tape.

Fortunately the tapes had been rewound properly, and the damaged portions of the tape were at a spot that was “beyond” the data area of the tape. After throwing on a fresh tension belt, and using one of my trusty Iomega Ditto drives (compatible with a wide range of this family of cartridges), I was able to dump and decode 100% of the data from them.

(As always, get in touch if you have any kind of vintage tapes or other media that you’d like recovered.)

Brain dump, September 2024

Custom IDE adapter for CP-4021 drive

As part of a special data recovery project, I needed to read the contents of the hard drive from an ancient Compaq LTE 8086 laptop. This hard disk, which is a Conner CP-4021, is quite an oddball. It has an unusual form factor: it’s a 3.5″ drive, but it’s slimmer and shorter than a regular drive, as if it was specifically made to fit into the LTE laptop.

Perhaps most annoyingly, the IDE connector on the drive is a very nonstandard half-pitch connector, where the pins have a horizontal pitch of 1.27mm, and a vertical pitch of 2.54mm. Inside the LTE laptop, this connects to a twin ribbon cable that goes directly to the motherboard, which basically means I have no way of connecting this drive to a “standard” modern IDE controller. (And it’s definitely an IDE drive, since the connector has 44 pins, just like any other laptop hard drive, and it has the same missing “key” pin as a standard IDE connector.)

Time to build a custom connector! After a whole lot of searching, I found a blank 50-pin header on AliExpress that should match the pitch of the drive’s connector. The 50-pin header will overshoot the 44-pin connector by a few pins, but it should still fit without issues. In an ultimate test of my fine motor skills, I soldered a spare 44-pin ribbon cable onto this 50-pin header, checking painstakingly that each pin on the female end matches the corresponding pin on the male end. To secure the delicate soldering onto the header, I covered it with clear epoxy, and let it harden overnight. And just like that, I have an adapter for connecting this ancient drive to a modern PC:

I then connected the drive to my workstation PC, and was encouraged when the drive spun up, and the PC detected the drive successfully! However, the PC didn’t seem to be able to read any actual data from the drive. After a good bit of head-scratching, and double-checking the continuity of all the pins of my adapter, and trying to connect the drive to a few other PCs, I had a last-ditch idea to rule out stuck heads or a locked spindle, which were rather common problems with older drives. I removed the top cover of the drive, exposing the heads and platter, and as the drive was spinning up, I gently turned the spindle manually away from its resting position. And wouldn’t you know it — this caused the spindle to come alive, and the drive became fully functional!

I was able to acquire an image of the drive in Linux with minimal effort (not a single bad sector!), and I’ll be keeping my fancy custom adapter in case I come across another drive like this in the future. I did a few more random Frankenstein experiments with the drive, including booting another vintage laptop from it:

…and connecting that laptop to another laptop via INTERLNK.EXE, which allows the C: drive on the “server” laptop to map as the D: drive on the “client” laptop, with the goal of transferring files from one to the other, or even dumping the entire partition, which I did with the SAVEPART tool.

The connection between the two laptops is a serial cable that I cobbled together from whatever I had on hand, which turned out to be an annoyingly short cable and, thankfully, a null-modem adapter, necessary for communication between the two serial ports. This resulted in a rather slow connection between the laptops; a parallel connection would be significantly faster, but I don’t have the appropriate cable. The INTERLNK tool (bundled with MS-DOS) worked just fine, and automatically detected the connection over the COM port.

T48 chip programmer, finally

I splurged on a proper chip programmer, the T48 by XGecu. Even though there is already a newer model of their programmer (the T56), the extra cost didn’t justify the few additional chips and features it supports, at least for me.

Along with the T48, I purchased a batch of random EEPROM chips for some initial testing and verifying of the T48 itself, and possibly for actual use in future projects. These are Winbond W27C512 chips, which have a rather unusual erase voltage of 14V and programming voltage of 12V, which will be a good exercise for the chip programmer.

The software for the T48 is for Windows only (there is an open-source alternative that supports an earlier model of this programmer (the TL866II), but it still has very limited support for the T48). And because the software is for Windows only, and especially because it requires a special driver which can only be installed with elevated privileges, I prefer to run it in a virtual machine, for reasons that I hope are obvious. Fortunately this is done very easily in VirtualBox, which supports USB passthrough effortlessly. Here it is, running in a Windows 7 (32-bit) VM, and communicating with the T48:

Since my batch of Winbond chips was suspiciously cheap, I assumed they were not “new”, but rather pulled from existing boards. And I was not mistaken: reading the chips, which worked absolutely fine, revealed that they already had contents in them:

And then, erasing and reprogramming the chips also turned out to be a breeze, which gives the T48 programmer a thumbs-up from me. As a special bonus, I removed the firmware chip from the Conner CP-4021 drive (mentioned above!) and was able to read the firmware, using one of the myriad adapters that were included with the T48 programmer.

The above chip is a Microchip 27C256 (32KB), in a PLCC-32 socket. Again, the T48 was able to read this 35-year-old chip without any issues, which makes me look forward to reading and programming many vintage and newer chips in the future.

Brain dump, August 2024

Compaq LTE Lite 4/25

Restored another vintage laptop: a Compaq LTE Lite 4/25! I got it practically for free from Craigslist, since it was in rather rough shape: the screen hinges were completely loose and no longer attached to the body. The laptop has clearly been dropped on one of the corners in the past, but miraculously the display ribbon cable was still intact.

Annoyingly, the LTE series of laptops doesn’t have a built-in BIOS setup utility, and requires a bootable “diagnostics disk” to set up the BIOS parameters. This took a bit of searching on the web, but I finally found the appropriate floppy disk image, and wrote it to a disk using my trusty Greaseweazle attached to an old floppy drive.

Now that I’m able to set up the BIOS, I can configure it to use a CompactFlash adapter as the hard drive, which is preloaded with all kinds of retro apps and games! But there’s a slight problem: the diagnostics program doesn’t allow us to set up a “custom” hard drive, and instead requires us to select one of the predefined hard drive types defined by Compaq. Bizarrely, the “custom” drive types appear in the list, but are not allowed to be selected! Fortunately there is a standard drive type #61 that is “close enough” to the size of my CF card (512MB), and uses the correct number of heads and sectors.

Selecting this drive type allowed the laptop to boot into the CF card and access its contents:

QIC tapes from TC2000 supercomputer

I got a request to recover the data from several QIC cartridges that came from a 1980s-era supercomputer: the TC2000, from a company called BBN.

This computer used a scalable RISC architecture that could be expanded to 128 CPUs. The “base model” of this computer had a sticker price of $350,000, which buys you things like a 25 MHz CPU, 16 KB of L1 cache, and 16 MB of RAM. It still boggles the mind that, today, a $1 SOC can blow these specs out of the water.

The QIC tapes are DC 600A cartridges (60 MB), which were read without any issues using my trusty Tandberg TDC-3660 drive. The tapes include the installation of the operating system for this computer (called “nX”, based on Unix 4.3 BSD), as well as some other programs and tools like Fortran and Lisp. Even though the tapes were exceptionally well preserved, they still needed the usual reconditioning steps of replacing the tension belt, and cleaning the debris left behind by the previous belt.

Unfortunately it looks like these tapes contain mostly binary files, intended to run on the architecture of the TC2000, so it’s highly unlikely they’d be runnable on any other system or emulator that I’m aware of. Still, an interesting bit of archaeology worth preserving.

Homeowner’s log, July 2024

I installed a soft-start unit in our air conditioning condenser. There have been a couple of annoyances with our AC system that I was hoping a soft-starter would solve:

The condenser makes a loud noise when starting up. This is due to the high inrush current that is supposed to kickstart the compressor. In reality, the compressor doesn’t necessarily need that much current to start, which is why a soft-start unit does the job of “ramping up” the current until it detects that the compressor has started.
When the condenser starts, the lights in the house flicker momentarily. This is also due to the high inrush current, but the root of this problem extends beyond our house. I believe this is caused by the power transformer that serves our entire street of houses; the transformer is improperly sized, and its capacity is too low to handle these spikes of current. This is also evidenced by the fact that our lights flicker just a bit when our neighbors’ AC unit starts.

After much research, I decided to go with the MicroAir Easy Start Flex. It’s a little pricey, but it’s intended to handle most types of condensers, regardless of its “tonnage”, referring to its BTU output (our condenser is a 5-ton unit, which translates to 60,000 BTUs.

Installing it was an absolute breeze, and took less than one hour. Afterwards, there was an enormous improvement in the startup noise, and the lights no longer flicker at all. I also made a video of the installation, with before- and after recordings of the startup noise:

If you’re considering installing one of these units in your AC system (which you should), make sure you’re completely comfortable working with household electrical wiring, completely familiar with the wiring of your AC unit, and take all the necessary safety precautions. If you are unsure about anything, please contact an HVAC professional.

Programming a chip programmer with another chip programmer

Recently I had a need to program a few Atmel ATtiny chips for a project, which I haven’t done in years. I rummaged through my drawers and found the necessary programming device, which is a USBasp device:

When I tried using it to program an ATtiny chip using the standard programming software (avrdude), it showed an error suggesting that I need to update the firmware on the programmer device.

$ avrdude -cusbasp -pt45
avrdude error: cannot set sck period; please check for usbasp firmware update
avrdude error: program enable: target does not answer (0x01)
avrdude error: initialization failed, rc=-1
        - double check the connections and try again
        - use -B to set lower the bit clock frequency, e.g. -B 125kHz
        - use -F to override this check

But the programmer device itself uses an Atmel chip (ATmega8a) that is only programmable using another chip programmer. What to do? Rummaging further in my drawers, I discover this contraption:

It’s an extremely cheap CH341A programmer (~$2 on AliExpress) that I’ve used in the past to dump the contents of BIOS chips on motherboards and video cards. However, perhaps it can be useful here? Looking on the back of it, we can see that it can definitely do SPI (it has MOSI and MISO pins, although the latter is misspelled “MIOS”!). Could it be that this other programmer is also supported by avrdude?

$ avrdude -c\?
Valid programmers are:
...
  c2n232i            = serial port banging, reset=dtr sck=!rts sdo=!txd sdi=!cts
  ch341a             = ch341a programmer (AVR must have minimum F_CPU of 6.8 MHz)
  dasa               = serial port banging, reset=rts sck=dtr sdo=txd sdi=cts
...

How fortunate! So, what if we just connect all the relevant pins from this programmer to our target programmer that is receiving the update:

I connected the GND, +5V, MISO, MOSI, CLK (which goes to SCK), and CS (which goes to RESET) pins from the programmer to the target, remembering also to put a jumper on JP2 to enable self-programming. I also obtained the latest firmware to be loaded onto the chip. And here we go:

$ avrdude -cch341a -pm8 -b19200 -U flash:w:usbasp.atmega8.2011-05-28.hex
avrdude error: initialization failed, rc=-2
        the programmer ISP clock is too fast for the target
        - use -B to set lower the bit clock frequency, e.g. -B 125kHz
        - use -F to override this check

Hmm, something about the ISP clock being too fast… but it suggests that we can use -F to override this check. OK, let’s try that:

$ avrdude -cch341a -pm8 -F -U flash:w:usbasp.atmega8.2011-05-28.hex
avrdude: AVR device initialized and ready to accept instructions
avrdude: device signature = 0x1e9307 (probably m8)
avrdude: Note: flash memory has been specified, an erase cycle will be performed.
         To disable this feature, specify the -D option.
avrdude: erasing chip
avrdude: processing -U flash:w:usbasp.atmega8.2011-05-28.hex:i
avrdude: reading input file usbasp.atmega8.2011-05-28.hex for flash
         with 4700 bytes in 1 section within [0, 0x125b]
         using 74 pages and 36 pad bytes
avrdude: writing 4700 bytes flash ...
Writing | ################################################## | 100% 1.25 s 
avrdude: 4700 bytes of flash written
avrdude: verifying flash memory against usbasp.atmega8.2011-05-28.hex
Reading | ################################################## | 100% 0.79 s 
avrdude: 4700 bytes of flash verified
avrdude done.  Thank you.

Wait, what? It worked! This is much easier than I thought it would be. Thanks, avrdude and cheapo CH341A programmer! I can now program ATtiny chips quickly and easily.