Digital DEC VT420 Terminal

Some pictures from inside a DEC VT420 from 1994. Wikipedia has some info on it here It is a 14'' device with 800x400 pixel, can handle up to 38.400 Baud.

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Monochrome tube with HV transformer.

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Closer look on main pcb. Below the shielded area I suspect the digital part of the device.

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Again HV section

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And again, now from the top

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Other side of main pcb

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There is some dust, but not too much.

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A Philips tube

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Model 32EBY114WRB, date code week 17, 1994

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From the left: serial connectors, a standard 25 pin serial connector, power plug.

Connecting the Terminal to a Linux Notebook

You need a real RS232<->USB level converter. Many USB<->RS232 converters create around 5 volts only, and that is not enough for the terminal. It requires a signal compliant to RS232 spec, and this is +12 volts (for a 0) and -12 volts (for a 1). I tried it with a simple one, that failed. Then with a good one ( Digitus USB to serial converter, offers 2 RS232 ports - nice) which fulfills the spec and works with the terminal. I also needed some gender changer, but this may be a problem due to my cables.

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The cheap, not working RS232 to USB adapter. It only creates 0 to +5V output voltage on serial linesRS232 to USB adapter.

In the following image, the voltage can be seen (value BY-AY), 4.92 volts only. (click to view larger version)  

The Digitus RS232 to USB adapter, fulfilling the RS232 spec, and it even has two outputs and some leds showing activity on the lines.

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In the following image the voltage created by this converter can be seen, its value BY-AY and its exactly 12.00 volts. (click to view larger version)  

After that, a terminal session can be started from Linux on the USBTTY port, e.g. on /dev/ttyUSB0.

There is a little issue with the keys, so there is no ESC key and also other important keys seem to be missing at first.

Further Reading