Thank you! I couldn't remember if I'd posted it here before, I've been off
the list for a while.
Because I don't know really anything about it, I'd been operating on the
belief the power sent from the PSU was DC. So maybe that's my issue. There
is a single 10 pin connector from the PSU to the motherboard. I tested for
DC and found the following:
Brown - +5V
Red - +5V
Orange - +5V
Yellow - -16V
Green - +16V
Blue - -0.8V
Purple - GND
Grey - GND
White - GND
Black - -2.4V
I'm not sure if the +16 and -16v need to be adjusted, or if they are that
high because they don't have a load during my testing. The -16V is directly
connected to the VEE on a nearby 1488, and I think the max voltage there
should be -15V.
The blue and black are the ones that didn't seem right. But, if they're not
DC then maybe that's my issue. Also last night I found more cold solder
joints, so maybe one or both are affected by that. I will test with my DMM
as AC instead of DC and see if I get something there instead. Barring that,
I'm working on a schematic of the PSU to try and figure out what it's
supposed to be delivering.
Like I said, very tempting to plug in, I suspect it may be just fine.. but..
there's a lot of chips to blow up here if I'm wrong.
-----Original Message-----
From: Brent Hilpert via cctalk <cctalk@classiccmp.org>
Sent: Wednesday, July 5, 2023 9:11 AM
To: General Discussion: On-Topic and Off-Topic Posts <cctalk@classiccmp.org>
Cc: Brent Hilpert <bhilp...@shaw.ca>
Subject: [cctalk] Re: 1974 No Name Terminal
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.
