Repairing a VT240.

Chris Zach cz at
Sun May 1 12:53:04 CDT 2022

> I find it rather annoying that with that much processor power there is
> no way to run a user program on the VT240. Maybe there is, but I can
> find nothing about doing that in the manuals.

"Power" is relative. If I recall the T11 was basically the four (five) 
Western Digital chips in one container that had the power of the mighty 
pdp11/03. Enough for a lot of basic stuff, but not so much a general 
purpose computer.

That said, it looks like the design and interfaces are pretty well 
documented and it does have access to the serial port so you might be 
able to build a ROM that includes RT11 or some kind of ODT. I think the 
printer port is also accessible so if you were seriously.... driven you 
might be able to get it to boot off a TU58.

> It's very like the Rainbow colour graphics board. There are a couple
> of programmed PALs in the memory update logic and I seem to remember
> that the ones in the VT240 and those in the 'bow are either identical
> or at least very similar.

Thought so. I just sold the Rainbow here, but I could see that the NEC 
graphics chip and a lot of the layout looked similar to the graphics on 
the Rainbow. I wonder if the Professional 380 AVO option used the same 
basic chipset.


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