TRS-80 Gebruikers Vereniging

Actief sinds 1 oktober 1978

De TRS-80 Gebruikersvereniging bestaat sinds 1978 en is de belangrijkste informatiebron voor de Tandy TRS-80 Model 1, Model 3 en Model 4 en aanverwante modellen. Het is de enige en belangrijkste bron in Nederland.

​A Portable TRS-80 Model-1


A Portable TRS-80 Model-1 is built into a plywood enclosure of about 42 x 36 x 7 cm (W x D x H), consisting of a keyboard, a do-it-yourself power supply, an Extension board and a 7" TFT-monitor.

Left side view, closed lid:

This TRS-80 Model-1 Level II has lower case, 256k RAM, Selector (to address the RAM and to switch to CP/M mode) and 3x speed-up (real 5.3 MHz, no wait states or anything like that). A Reset button (NMI) and a Switch to select low (1.77MHz) or high speed (5.3MHz) are mounted on the back of the keyboard. The ribbon cable between Keyboard and Extension board can be seen on the left side.

The Extension board provides a CF-Card/IDE hard disk interface, USB mass storage (two USB ports), a bidirectional 8-bit parallel port, and an interrupt driven 25 ms (40 Hz) heartbeat. These two USB ports and the bidirectional parallel port are exposed on the left side of the enclosure.

The USB ports can be used for FAT-16 or FAT-32 formatted mass storage devices, like memory sticks. A file copy program is written in Basic (listing available). If proper drivers are used, other USB- devices might be connected, such as USB-mice or any other (slave) (serial) USB-device.

The bidirectional 8-bit parallel port can be used as a standard TRS-80 printer port. In addition it may be used in full duplex mode with 8-bits output and input with separate strobe and status. The 8-bits input are latched and may be used interrupt driven (software and/or driver not yet available). With a proper cross cable, the input side may be used to receive another computer’s printer output.

If a real TRS-80 Expansion Interface (EI) is connected, the bi-directional 8-bit parallel port and the heartbeat function can be disabled under software control to avoid conflicts with the heartbeat and printer port in the EI. Yet, even with a real EI connected, the computer can directly boot from the CF- card.

Right side view, closed lid:

The right side has a power on-off switch, a USB 2A 5V power outlet and a cooling plate.

The USB power outlet may be used to charge USB-devices like MP3-players (might be used as an alternative cassette player), (smart-)phones and so on. In addition, it may be used as a power supply for additional hardware.

The cooling plate consists of an aluminium angle profile, that is used to cool a 7805 (5V Extension board) and a 7812 (12V TFT-monitor) DC power stabilisation.

The power cord may be stowed away under the lid, winded around the 7"TFT-monitor.

In use, left and right side view:

In use, front view:

The hard disk volumes of this CF-card are configured as follows:

1) Newdos/80 (a bootable modified version of Newdos 2.5)

2) Several volumes with TRS-80 programs and games

3) LDOS 5.3

One might switch between Newdos and LDOS operating systems at will.

Newdos has a command “LDOS,” that switches to LDOS. LDOS has a command “Newdos,” that switches to Newdos.

The hard disk data volumes (with programs and games) are common to Newdos and LDOS.

Inside view:

The power supply (on the right) supplies power for the M1-keyboard, a TRS-80 Expansion Interface (if present), the Extension board, the 7" TFT (car rear view) Monitor, and a 5V, 2A USB-connector for additional hardware or to power or charge USB devices, like (smart-)phones, USB-fan, USB-lamp, or any other USB device that needs a power supply (2A max).

The Extension board supports an IDE-interface (any IDE mass storage device), a USB-interface (currently for mass storage devices), a bidirectional 8-bit parallel port and a 25 ms, 40 Hz heartbeat. As such, it replaces the Expansion Interface except for Floppy drives, 2nd cass. recorder and RS-232.

Inside view, close up:

On the left, the Extension board with (CF-card) IDE interface, parallel port, USB-interface and 25 ms heartbeat. A (standard) TRS-80 Model-1 Expansion Interface may be connected to the connector next to the ribbon cable.

In the center a single 2 x 6V, 4.16A, 50W transformer.

On the right the power supply with 2 diodes to get 5V DC from the center tapped 2 x 6V windings. A 7805 is used to stabilize the 5V for the Extension board and a DC-DC step-down buck converter is used for the 5V 2A external USB power connector. To get 12V DC, voltage doubling is obtained, using a bridge rectifier. A 7812 is used to stabilize the 12V for the 7" car rear view TFT monitor (150 mA).

Both the 7805 and the 7812 are mounted to the same aluminium angle profile for cooling (one part of this angle profile can be seen from the outside of the enclosure).

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