Tandy Portable Disk Drive 2

So following along from getting my REX installed and playing with it, the next addition for my little M100 kit was a Tandy Portable Disk Drive 2:

As the name suggests, its a portable 3.5" disk drive that goes with the Model 100, can run on AA batteries or 6V DC and reminds me very much of a top loading VCR we owned a long time ago.

The drive itself appeared in fantastic cosmetic condition when it arrived - however it did not come with the serial cable to connect it to the M100 nor any disks.  I didn't think the missing cable would be a huge deal - but as it turns out I should have asked the question before purchasing the drive.  The cable is not just a straight serial cable, and has to adjust some of the voltage levels between the M100 and the drive to get things to work.  I started looking online at the documentation people have produced around making your own cable.  It was at this point someone very kindly offered me a spare cable that they had excess to their needs and posted it to me.  To that individual - thank you!

Once I had that cable I was ready to give the drive a good clean and service.  I had also ordered a replacement drive belt and some double sided, double density disks in the meantime too - which had also arrived.  The drive will only read one side of the disk, and only format it to 200K, but they work.  The drive only requires a few screws be removed for the plastic case to come off:

With the top, bottom and front plastic casing removed, the drive came out as a single unit.  It was at this point that I gave all of the plastics a good clean.  Removing a few more screws allowed the shielding to come off and the main PCB was revealed:

Removing one more screw allowed the PCB to be separated from the drive:

As you can see in the photos the drive was very clean inside, which was a nice change.  At this point I replaced the drive belt:

You can see how stretched the old one was compared to the new one.  I also lubed up all of the mechanical parts in the drive.  I then turned my attention to the small power supply PCB:

The six capacitors all actually looked pretty good - but I replaced them anyways:

As a last step I gave the drive head a good clean with some isopropyl alcohol and reassembled the drive.  I then grabbed the serial cable and plugged the drive into my M100:

I then turned on my M100, went into TS-DOS, hit F4 to bring up the disk menu and after a brief read of the disk, it showed the disk in the drive as unformatted:

So I formatted the disk - which worked first go:

I then saved a file to the disk, and read it back from the disk.  All worked as expected:

I now own a vintage portable storage solution for my M100!

M100 REX

My last post was about the SuperROM that I received with one of the M100's I purchased.  Now that my M100 was fully functional I started to look at what little extra bits might be fun to play with.  One of the major bits was the REX.  The summary of the REX taken directly from the wiki:

• REX allows for storage and quick, easy switching between OPTION ROM images. Once the binary software images are loaded into REX, the user can easily jump back and forth between different applications.
• REX provides the ability to backup and swap working RAM images. At the press of a key, your current RAM contents are saved in REX. Furthermore, you can reload any saved RAM image for use. This creates a library of RAM images, which has a number of uses. This offers an easy way to quickly backup all RAM to flash, or switch between multiple snapshots of RAM. It is like having multiple laptops in the same case!
• REX includes an interface to TPDD devices (like TPDD, NADSbox, LaddieCon etc) for loading and saving binary images to external storage.
• REX modifies they way MENU displays the date, effectively fixing the Y2K 'bug'.

I didn't realise how awesome the REX was until I got one:

As stated above it adds both different OptionROMs which itself is pretty awesome as the M100 community has developed some pretty awesome custom OptionROMs for the M100.  The extra tools and updates/bug fixes in some of the OptionROMs blew me away.  The REX also adds some flash storage to backup and restore the flash contents of the M100.  Remembering the M100 has no persistent storage - if the main batteries and backup battery all go flat you lose all your data.  This is super handy.  I plugged it in and loaded it up.  The new menu looks pretty cool (with the correct date thanks to the Y2K fix):

It's super easy thanks to the built in menu of the REX to change OptionROMs or save/restore multiple flash contents.  This little guy will come in super handy playing around with my M100 - thanks to all that worked to make the REX a reality!

PCSG SuperROM

As mentioned briefly in my last post - I ended up with  Portable Computer Support Group (PCSG) SuperROM.  This guy is a ROM addon for the Model 100 that includes four additional applications:

• Lucid
• Write Rom
• Thought
• Lucid Data

I found the scanned manual for this guy where I have found most of the scanned manuals I need - the Club 100 Library page.  It's a pretty basic install and setup.  Power the 100 off (not the memory power switch - just the main switch), flip the device over and open the expansion bay:

The top is the system bus, the bottom is the expansion ROM slot where the SuperROM goes - simply push it in:

From there flip the unit back over and power it on.  At this stage you shouldn't see any difference in the display - it should just be the menu you are used to:

If this worked you are good, if it didn't maybe try reseating the ROM and try again.  From here to tell the unit the ROM is installed, open the Basic prompt and type:

call 63012

This should open the SuperROM menu:

From here you can open any of the included apps, or jump back to the main (normal) menu by hitting F8.  When you do though you will have an additional menu option "super" which will jump you back to the SuperROM menu:

This stays there as long as the unit doesn't lose complete power (the RAM battery backup).  Pretty handy really.  I'll give the apps more of a test - but they all opened and appeared to run as they should.  #winning

Portable retro!

So I have always loved small portable electronics - and retro is no exception.  There is a portable retro machine I have always love the look of - so about six months ago I started searching for one that wasn't going to require me to take a loan.  I found one that was listed as non-working/parts only but great cosmetic condition, going cheap and so I took a punt:

The computer that Bill Gates himself last wrote software for, the Radio Shack TRS-80 Model 100:

It showed no sign of anything when given power and turned on - as stated in the ad.  I left it plugged in for a while, as all the documentation around this guy says the internal battery needs a decent charge for the display to function 100%.  This didn't make a different though (not suprising when you see below).  This thing was cosmetically almost perfect.  No yellowing or scratches - thats a good start.  Better yet it came with this guy:

A "SuperROM" expansion rom (more on this in a future blog post).  Unfortunately this is were the good news finishes.  I opened it up to see what I was dealing with:

I was greeted with a pretty acidic smell and corrosion pretty much everywhere!  I haven't seen something this bad in person before.  Take a look at the ribbon cable connector for the LCD:

Most of the electrolytic capacitors had let go too:

I removed all of capacitors that had let go:

I then cleaned up the board as best I could:

And replaced all of the capacitors.  Unfortunately it made no difference.  No sign of life on the display.  I used the troubleshooting guide (and stopped taking pictures - sorry!), which said start with metering the various voltages put out by the power supply.  None of these were right!  I cheated and instead of trying to diagnose any supply issues, I used my bench supply to provide the various required voltages - unfortunately this too made no difference either.  Every different output i tried to measure, from just checking voltages supplied to chips, to reset lines, data lines and everything in between.  Nothing.

This was just before Christmas.  I left all of this to sit on the bench for a bit while I enjoyed some time with family and friends away from screens of any sort.  At the start of January I had another crack at the board - but couldn't get it to show any signs of life anywhere.  So while I continued to play, I kept looking online to see if I could find another unit that might have a better chance of being brought back to life.  I was lucky enough to find exactly what I was looking for - a unit in "average" cosmetic condition, but in working condition going for a lot less than these things commonly go for - and so I bought it.

This is the first time I have "given up" and not been able to fix something.  This annoyed me a little - but is also a risk you take buying 30+ year old electronics online.  I waited for the second unit to arrive, and got straight to work when it did:

It was quite yellow (more so than shows in the picture above), it had a rattle when I moved it and it also wasn't screwed shut.  However - it worked!  The display wasn't great but I could see what I was supposed to when I powered this guy up - thats a good start!  I took a breath and opened it up to see what this unit might hold.  I wasn't super excited when I took the four case screws out and one of the four was obviously a replacement - and a poor one at that:

The board looked pretty good (I guess anything wold compared to the last unit):

I then discovered what the rattle was, and why the case didn't seem to be screwed shut despite having all four case screws done up tight - two of the stand offs on the bottom of the top half of the case had snapped off and were rolling around inside the case (bottom two corners):

This is what I found rolling around inside:

Looking around for signs of corrosion I didn't see much at all.  The battery looked like it had just started to let go - lucky!  So out it came:

There was a small amount of corrosion on the board - but nothing that didn't clean right off with some isopropyl alcohol:

I put a new battery in, and then had a look at the capacitors.  I couldn't see much - but thought for the small cost of recapping why not rip them out - I'm glad I did:

Most of the ones I pulled out showed signs of letting go like those above.  Again I think i got super lucky and caught these ones just in time!  There are a couple of larger capacitors I didn't have replacements for - so I will come back and replace them in the near future.  From here I decided to take a look around the board more generally.  The DB25 RS232 port on this guy was pretty gross - I don't know what the previous owner had done to it.  The installed RAM expansions also stood out a little:

So since I now have a spare - I thought why not switch them out?  So that's what I did.  I removed the DB25 and soldered RAM from the non-working unit:

I had to remove the DB25 from the working unit, the RAM expansions though are socketed - so just needed to be removed (no de-soldering required).  Once that was done I installed the replacement parts and put the board back in the case from the non-working unit (that was in fantastic condition):

I swapped the LCD from the working unit into the non-working units case (given the corrosion you saw on the connector alone above) and took the keyboard out and gave it a good once over.  At that point I put the whole thing together.  Low and behold - my new working 32K TRS-80 Model 100 computer:

I've got a few things to try with this guy now that it's working - but that will be the topic of another blog post some time soon I hope.