Deminsions

ntThe Tandy TRS-80 Model 100 measured 11.8 inches wide by 8.5 inches tall by 2 inches thick. It weighed just over 3 lbs. (with four AA batteries).

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ntPhoto by: Bill Detwiler
ntCaption by: Bill Detwiler

Made in Japan

ntThis TRS-80 Model 100 was manufactured in Japan by Kyocera for Tandy/Radio Shack.

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ntPhoto by: Bill Detwiler
ntCaption by: Bill Detwiler

FCC sticker

ntPhoto by: Bill Detwiler
ntCaption by: Bill Detwiler

Memory Power switch

ntThe Model 100 has a Memory Power switch. If the 4 AA batteries ever go dead or are removed, the switch let’s you use the CMOS battery to power the memory and store data.

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ntPhoto by: Bill Detwiler
ntCaption by: Bill Detwiler

TRS-80 Model 100 and 2010 MacBook Pro

ntThis photo shows the Tandy TRS-80 Model 100 next to a 2010 MacBook Pro. It’s interesting to see how much thinner today’s machines are.

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ntPhoto by: Bill Detwiler
ntCaption by: Bill Detwiler

Optional ROM sockets

ntYou could add programs to the TRS-80 Model 100 through preprogrammed ROMs, which could be installed here.

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ntPhoto by: Bill Detwiler
ntCaption by: Bill Detwiler

External case screws

ntUnlike many of today’s portable computers which use special tamper-resistant screws, the TRS-80 Model 100 uses standard Phillips screws. There are four external screws that need to be removed.

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ntPhoto by: Bill Detwiler
ntCaption by: Bill Detwiler

Opening the case

ntWith the four external screws removed, you can lifting the top half of the case away from the bottom. There are several cables that connect the two halves, so lift up from the machine’s left side (where the bar code reader port is).

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ntPhoto by: Bill Detwiler
ntCaption by: Bill Detwiler

Two halves still connected

ntLuckily, the internal cables on the TRS-80 Model 100 are long enough to lay both halves next to each other.

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ntThe motherboard and ports remain in the lower half of the case, while the display, keyboard, and internal speaker are attached to the top.

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ntPhoto by: Bill Detwiler
ntCaption by: Bill Detwiler

Disconnecting the internal cables

ntYou’ll need to disconnect the cables for the display, speaker, and keyboard before separating the two halves of the TRS-80 Model 100.

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ntPhoto by: Bill Detwiler
ntCaption by: Bill Detwiler

Display, keyboard, and speaker still attached

ntThe display, keyboard, and speaker are attached to the top half of the the TRS-80 Model 100’s case.

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ntPhoto by: Bill Detwiler
ntCaption by: Bill Detwiler

Motherboard, memory, and ports still attached

Removing the keyboard screws

ntFive Phillips screws hold the TRS-80 Model 100’s keyboard in place.

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ntPhoto by: Bill Detwiler
ntCaption by: Bill Detwiler

Disconnecting the speaker wire

ntThe TRS-80 Model 100’s internal speaker is connected to the display’s PCB with a thin wire. You’ll need to disconnect this wire before removing the display assembly.

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ntPhoto by: Bill Detwiler
ntCaption by: Bill Detwiler

Removing the LCD display assembly screws

ntFour Phillips screws hold the TRS-80 Model 100’s LCD display assembly to the upper half of the case.

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ntPhoto by: Bill Detwiler
ntCaption by: Bill Detwiler

LCD display assembly removed

ntWith the screws removed, you can lift the Model 100’s display screen and PCB away from the case.

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ntPhoto by: Bill Detwiler
ntCaption by: Bill Detwiler

Monochrome LCD display screen

ntThe TRS-80 Model 100’s monochrome LCD display provides a resolution of 240 x 64 pixels and can show eight lines of text. The screen was not backlit.

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ntPhoto by: Bill Detwiler
ntCaption by: Bill Detwiler

Hitachi HD44102 Dot Matrix LCD Column Driver Chip

ntThere are several large Hitachi HD44102 Dot Matrix Liquid Crystal Graphic Display Column Driver chips mounted to the back of the display’s PCB.

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ntPhoto by: Bill Detwiler
ntCaption by: Bill Detwiler

Hitachi HD44103 Dot Matrix LCD Common Driver Chip

ntAlong with the HD44102 chips, there are two Hitachi HD44103 Dot Matrix Liquid Crystal Graphic Display Common Driver chips mounted to the display’s PCB.

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ntAccording to documentation on Alldatasheet.com, the smaller HD44103 chips generate the timing signals required for display with their internal oscillator and supply them to the HD44102 column driver to control the display.

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ntPhoto by: Bill Detwiler
ntCaption by: Bill Detwiler

Hitachi HA17902 Quad Operational Amplifier

ntA single Hitachi HA17902 Quad Operational Amplifier is also mounted on the display’s PCB.

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ntPhoto by: Bill Detwiler
ntCaption by: Bill Detwiler

Removing the internal speaker

ntThe TRS-80 Model 100’s internal speaker is held to the frame with clear, plastic screws. I used a #00 Phillips screw driver bit to remove them.

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ntPhoto by: Bill Detwiler
ntCaption by: Bill Detwiler

Internal speaker removed

ntPhoto by: Bill Detwiler
ntCaption by: Bill Detwiler

Disassembling the lower half

ntWith the upper case completely disassembled, let’s turn out attention back to the lower half of the TRS-80 Model 100.

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ntPhoto by: Bill Detwiler
ntCaption by: Bill Detwiler

Disconnecting the green ground wire

ntThe first step in removing the TRS-80 Model 100’s motherboard from the lower half of the case is to disconnect the green ground wire.

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ntPhoto by: Bill Detwiler
ntCaption by: Bill Detwiler

Removing the power connector

ntAfter disconneting the ground wire, you can lift the power connecter away from its slot in the case. You do not need to disconnect its wires from the motherboard.

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ntPhoto by: Bill Detwiler
ntCaption by: Bill Detwiler

Removing the serial and printer port cover

ntAlthough it’s not necessary to remove the plastic bar that covers the serial and printer ports, I went ahead and did so.

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ntPhoto by: Bill Detwiler
ntCaption by: Bill Detwiler

Lifting the motherboard away from the case

ntWith the screws removed, you can lift the TRS-80 Model 100’s motherboard away from the lower half of the case.

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ntPhoto by: Bill Detwiler
ntCaption by: Bill Detwiler

Lower half of the case - Empty

ntThere’s nothing left in the case but a thin metal shield and attached ground wire.

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ntPhoto by: Bill Detwiler
ntCaption by: Bill Detwiler

OKI Processor and Toshiba RAM

ntThe main points of interest in this corner of the motherboard are the OKI MSM80C85ARS processor (upper left), D3-6402-9 UART chip (upper right), and Toshiba TC5518BF-25 RAM (lower right).

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ntPhoto by: Bill Detwiler
ntCaption by: Bill Detwiler

2.4MHz 80C85 processor (MSM80C85ARS)

ntThis Model 100’s Intel 2.4MHz 80C85 CPU was manufactured by OKI and has markings MSM80C85ARS.

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ntPhoto by: Bill Detwiler
ntCaption by: Bill Detwiler

Toshiba TC5518BF-25 RAM

ntToshiba TC5518BF-25 RAM

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ntThis unit has 8Kb of RAM.

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ntPhoto by: Bill Detwiler
ntCaption by: Bill Detwiler

D3-6402-9 UART chip

ntThis D3-6402-9 UART chip drives the TRS-80 Model 100’s RS232 serial port.

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ntPhoto by: Bill Detwiler
ntCaption by: Bill Detwiler

MC81C85RS I/O controller chip

ntThis MC81C85RS I/O controller chip drives the keyboard, parallel printer, speaker, clock, and LCD.

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ntPhoto by: Bill Detwiler
ntCaption by: Bill Detwiler

Option ROM socket solder points

ntBelow the serial connector and I/O controller chips and to the right of the RAM chip, there are solder points for the option ROM sockets, which are mounted on the underside of the motherboard.

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ntPhoto by: Bill Detwiler
ntCaption by: Bill Detwiler

Sharp LH535618 ROM

ntThis Sharp LH535618 ROM chip contains the TRS-80 Model 100’s built-in software, such as BASIC.

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ntPhoto by: Bill Detwiler
ntCaption by: Bill Detwiler

Toshiba TC40H chips

ntThere are many different Toshiba TC40H chips mounted around the motherboard, which are used for the keyboard.

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ntPhoto by: Bill Detwiler
ntCaption by: Bill Detwiler

CMOS battery

ntAs noted eariier, this 3.6V rechargeable battery would power the information stored in memory if the four AA batteries were removed or went dead.

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ntPhoto by: Bill Detwiler
ntCaption by: Bill Detwiler

PLX100CH1X motherboard marking

ntThe motherboard on this TRS-80 Model 100 has the marking PLX100CH1X.

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ntPhoto by: Bill Detwiler
ntCaption by: Bill Detwiler

Complete disassembled

ntThanks to TRS-80 Model 100’s standard Phillips screws and sturdy construction, cracking it open was an simple and enjoyable process. It’s also interesting to see how the internal components of notebook computers have change in 28 years.

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ntYou can find out more about the Tandy TRS-80 Model 100 with the following links:

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• nttModel 100 Technical Reference Manual

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• nttTandy Model 100 Service Manual

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ntPhoto by: Bill Detwiler
ntCaption by: Bill Detwiler