Cracking Open the Radio Shack TRS-80 Model 4P
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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.
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.
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.
Finally some insides
After removing the plastic and the back plate we actually start to see some electronics.
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.
The power connection at the top of this image looks very similar to what is used today.
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.
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.
More power management
There is another side panel dealing with power.
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.
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.