While the Osborne 1 claims to be the word's first self-contained portable personal computer, the Radio Shack TRS-80 Model 4P can lay claim to being one of the next generation of portable computers. Eerily similar to the Osborne 1, the Model 4P made major strides in construction and usability. This TechRepublic Cracking Open Photo Gallery reveals how the TRS-80 Model 4P improved upon the initial luggable design to takes its place in the history of portable personal computers.
New and improved
The most obvious improvement with the TRS-80 Model 4P is the much larger video screen.
Getting into the keyboard just required the removal of a few screws.
As with the Osborne and other dinosaur PCs we have looked at, the old-fashioned mechanical keyboard and its tell-tale clacking sound is notable. They don't make like this much anymore.
I don't know why she swallowed a fly
I've seen crumbs in a keyboard but this is my first dead fly. I don't even want to guess how long that has been in there.
The Model 4P connects to the keyboard in a relatively conventional cable.
According to John Sheesley, Radio Shack used Fujitsu for all of the keyboards back in the early 1980s.
Voiding a warranty
Our TRS-80 had a warranty as late as 1987. But we have to void it to get inside -- oh well.
Getting the outside plastic case removed was slightly complicated by the unit's handle.
I can handle it
The screws attaching the handle to the case also attached the case to the interior chassis. It took me a few minutes to figure it out. From a portability point of view, it makes sense.
More to go
Removing the out case reveals an enclosed inner chassis -- not something I expected to see. The Model 4P is built to last.
Even the floppy disk drives are encased in some sheet metal.
The all metal back plate is very solid and gives the handle a good base to attach to -- portable indeed.
Finally some insides
After removing the plastic and the back plate we actually start to see some electronics.
Of course the first noticeable part we can see is the Cathode Ray Tube (CRT) for the video display.
The same image with the camera flash. Hey look a fan, that is something the Osborne 1 did not have.
The top of the interior case is where the power regulation takes place. Here we go with the warnings again. However, I did not that 250 Volt capacitor there -- I was very careful with this part.
Similar to the Osborne 1 there is an old-fashioned fuse in the TRS-80.
I get the distinct idea that there is some high voltage running through and or out of that transformer.
The power connection at the top of this image looks very similar to what is used today.
The main circuit board of the TRS-80 Model 4P.
These RAM chips are more compact then they were in the Osborne 1.
There are dozens of silicon chips om the motherboard. Just think how the function of many of these chips are reduced to a single chip now.
Here is our first look at the Z80 processor inside our TRS-80 Model 4P.
Now, that's Italian
Our version of the Z80 CPU is stamped as arriving from Italy. That is a new country of origin for our cracking open series as far as I can tell.
We have a Toshiba chip on the board.
We continue the international theme -- we see some chips from the Philippines and the Texas Instruments logo is prevalent. Of course, we can also see numerous chips from Motorola.
Okay, don't chastise me if I am wrong, but the chip with the label seems to me to be a ROM chip.
One of hazards of opening these really old PCs is that they are often dirty. I wonder how toxic that dust is?
One thing I like about Radio Shack is that the company appreciates the value of technical specifications. That PDF should give the engineers or just the curious plenty of technical information to wade through.
El Salvador is represented just as it was in Osborne 1.
This is the first SMC reference I remember seeing in these two old luggables. A floppy disk controller?
There is a familiar name -- Western Digital. But according to the technical specification reference sheet, this chip also plays an integral role in the video display of the TRS-80.
All cracked open
More power management
There is another side panel dealing with power.
A closer look
Here is a closer look at the CRT. There is a serious warning on the back of the housing here too.
The TRS-80 Model 4P saves some space by using 1/2 height floppy drives and packing them tightly together.
The glued piece shown here is hanging on -- but just barely.
A better look
A look at the CRT and the warning message with the flash on.
There are a couple of notes on the floppy drives indicating that they have been serviced.
A last look
One last look at the cracked open TRS-80 Model 4P.
Almost invariably when I do a cracking open I receive a comment about how I killed the object in question. This is proof that the TRS-80 Model 4P is alive and well after I put it back together.
Overall, I can say with confidence that this portable (luggable) is a better, more well-constructed, personal computer than the Osborne 1.
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By Mark Kaelin
Mark W. Kaelin has been writing and editing stories about the IT industry, gadgets, finance, accounting, and tech-life for more than 25 years. Most recently, he has been a regular contributor to BreakingModern.com, aNewDomain.net, and TechRepublic.