Cracking Open the Tandy Model 100

Here's the back of the unit. There are four screws on the corners to be removed.

The serial number of the unit. The computer was made in Japan by Kyocera for Radio Shack.

Here's the FCC rating. The Tandy Model 100 was an FCC Class B machine meaning it could be sold in homes as well as businesses because it didn't give off much radio interference.

The battery door removed revealing the holder for the 4AA batteries that powered the unit.

The Optional ROM sockets. Here you'd add programs to the Model 100 that were packaged in preprogrammed ROMs.

This is the switch that controls the onboard CMOS battery. It's used to store data in the unit if the 4 AA batteries are removed or go dead. When the unit is being used, this switch is ON. For storage purposes, you turn it OFF.

The patient is ready to be opened.

The unit separates into two halves, butterflied open as you see here. The main system board is in the bottom part of the unit (on the left) the screen and keyboard are in the top (on the right).

Here's the main system board of the Model 100.

Here you see the display and keyboard circuit boards.

The video connector is separated here. Below that you can see the connector for the speaker (two wire white and read). The two connectors for the keyboard are at the bottom.

The right side detached from the unit.

This is the backside of the keyboard. Nothing to see here.

Ah... but wait! There is. There's an ALPS logo, showing who made the keyboard.

Here's the front of the keyboard.

Removing the keytops reveal actual switches beneath the keys. Modern keyboards usually just have dimpled rubberized contacts. These switches give the Model 100 it's solid typing feel.

Here you can see the chips on the back side of the LCD. The large chips are HD44102CH LCD driver chips.

To the left you can see the speaker connector wire and the wide LCD ribbon cable.

More of the HD44102CH LCD driver chips.

To remove the LCD, you must disconnect the speaker that's beneath the panel.

The LCD panel removed.

The lone LED on the left of the LCD panel is for displaying Low Battery status.

This is the top shell of the Model 100 with the LCD and Keyboard removed.

The blue circle is the speaker.

Close up of the Tandy Model 100 speaker.

The system board of the Model 100.

The upper right hand corner of the system board. You can see the underside of the battery compartment.

A close up of the LCD contrast dial. Beneath it, you can see the on/off switch.

The colored wires connect the DC adapter to the system board.

The lower right hand corner of the system board.

The Toshiba TC40H138P chips are multiplexer chips used by the keyboard.

Next to it is a large Sharp LH535618 ROM chip. This contains BASIC and the menu information for the Model 100.

Here's the only real identifying information on the system board - PLX100CH1X.

This code identifies this Model 100 as being an early model unit.

Here you can see the backside of the ROM upgrade sockets on that were on the underside of the unit. The SHARP ROM is o the right.

On the left on the gray/purple card are the RAM chips for the unit. This unit has a total of 8K RAM.

Next to the installed soldered 8K RAM, you see 3 more empty RAM sockets. The unit was expandable to 32Kb RAM by filling these sockets.

Here's the Model 100 CPU. It's an 80C85. The 80C85 is a CMOS low-power version of the Intel 8085.

The 80C85 is an 8 bit CPU running at 2.5Mhz

These two large chips sit in the center of the board next to the CPU.

The D3-6402-9 chip is a UART chip that drives the Model 100's RS232 port.

The MC81C85RS chip next to it is an I/O controller that drives the keyboard, parallel printer, speaker, clock, and LCD.

Here's where the onboard 300bps modem is. You can see the relays and transformers used to make rotary dial calls.

To the left you can see the switch that controls whether you're using a direct connect cable or a set of acoustic couplers.

Here you can see the Reset switch at the top right.

The round brown unit in the center is the backup battery for the Model 100.

The Tandy Model 100 completely cracked open.