On 2023-Jul-05, at 8:25 AM, Brad H via cctalk wrote:
> Seems to be RS-232 compatible, which in my experience is unusual for a
> terminal in the early half of the 1970s. It has little serial number
> stickers tucked around but they're all random numbers, nothing really lines
> up. A few of the boards have what appears to be serial numbers in the low
> hundreds.
>
> So tempting to just plug in and see what happens, but I'm concerned about the
> voltages on two pins that seem off.
What does 'seem off' mean?
One possibility is they are a floating supply for the CRT heater. Not unusual
in those days was just to have an independent 6.3 or 12.6 VAC secondary on the
PS transformer dedicated to the heater and it often wouldn't be grounded. You
could try checking between the two pins with multimeter ACV range.
This terminal (this specific unit) was mentioned on the list 2 years ago:
https://classiccmp.org/pipermail/cctalk/2021-February/thread.html#57808
2021-Feb-12
Mystery (unusual) 1973 terminal
Around a dozen messages. In one of those messages I list & ref some of the
more-significant ICs from the board photos.
