[TUHS] Re: AT&T UNIX PC (7300) Teardown and Restoration

[Warner Losh <imp@bsdimp.com>]

[-- Attachment #1: Type: text/plain, Size: 4260 bytes --]

On Tue, Jan 3, 2023, 5:30 PM segaloco via TUHS <tuhs@tuhs.org> wrote:

> I'd love to get my hands on a 3B2 someday, this'll be cool if I can get it
> going but that'd be a much more robust machine.
>
> I'm starting to suspect if there isn't any sort of boot ROM that spits out
> commentary on the UART and that doesn't get flexed until UNIX is up, I may
> not be able to get very far. I referred to
> http://bitsavers.trailing-edge.com/pdf/att/3b1/999-809-010IS_UNIX_PC_Remote_Access_1986.pdf
> for the serial settings and it appears:
>
> 9600 baud, 1 stop bit, no parity, 8 data bits
>
> And the relevant pins
>
> Pin 1 - GND
> Pin 2 - RX
> Pin 3 - TX
> Pin 4 - RTS
> Pin 5 - CTS
> Pin 6 - DSR
> Pin 7 - GND
> Pin 8 - DCD
> Pin 20 - DTR
>
> So I've plugged my USB-TTY GND/RX/TX into the relevant pins and setup the
> necessary tty settings. The manual then suggests if running null modem mode
> to short pin 4 to 5 and then pins 6, 8, and 20 together, presumably
> omitting any need for modem signalling from the remote machine, doing basic
> serial RX/TX. Unfortunately even with all of this bypassing I get nothing
> out of the RS-232 port. What I don't know is if I could even expect
> something or if this is unlikely to bear fruit whether the hardware works
> or not. In any case, if I do get this thing running I'll have a writeup for
> folks afterwards. If not, then hopefully I can figure out something useful
> to do with this thing rather than junking it.
>

Silly question... did you level shift to RS 232 levels? You likely did...
but if not...

Warner

- Matt G.
> ------- Original Message -------
> On Tuesday, January 3rd, 2023 at 3:53 PM, rob@atvetsystems.com <
> rob@atvetsystems.com> wrote:
>
> Hello Matt,
>
> I’ve got one of these in my garage. I bought it about twenty years ago as
> a working system but when I got it home I noticed that the hard disk wasn’t
> connected but at some point I’d like to get it and my 3b2/300 working.
>
> Regards, Rob.
>
> On 3 Jan 2023, at 23:27, segaloco via TUHS <tuhs@tuhs.org> wrote:
>
> And here are some pictures of the guts.
>
> https://imgur.com/a/E1ioxZl
>
> Various bits inside date this to late 1985. The good news is it at least
> turns on, but that's about as far as I've gotten with it. The display never
> turns on, nor do I hear any sounds indicating it tries to start the CRT.
> The fans kick on and there it stays until I turn it off. I plugged in a
> USB-TTY to pins 2, 3, and 7 (RX/TX/GND) and listened at 9600 baud 8 bit 1
> stop no parity and got nothing. Swapped the RX/TX, still nothing. Of
> course, that's all predicated on the assumption there's something there to
> even interact with. I have little faith that whatever UNIX install was on
> this is extant. Additionally, it didn't come with a keyboard, so if there
> was some futzing with key combos that would trigger some sort of UART over
> those lines, I can't do that. I wonder if there are some contacts inside I
> can just poll for activity with this serial connector, not sure how safe
> that is...
>
> Anywho, the CPU has a bit of corrosion on the surface, not sure how that
> bodes for the innards, but this is in kinda rough shape either way. I hope
> I can salvage it but if not, I'm going to at least do some study on the CRT
> particulars and see if I can extract and keep the monitor from it, been
> wanting a smaller CRT to have around for a while.
>
> - Matt G.
> ------- Original Message -------
> On Tuesday, January 3rd, 2023 at 12:20 PM, segaloco via TUHS <
> tuhs@tuhs.org> wrote:
>
> Good day everyone, just starting a thread for yet another project I'll be
> tinkering on over time. Picked up a (presumably broken/untested) 7300 off
> eBay to at the very least tear down and get some good pictures of and, with
> some luck, perhaps get working again.
>
> https://imgur.com/a/CExzebl
>
> Here are some pictures of the exterior for starters. I'll update this
> thread when I've got pictures of the guts and also with any info I can
> glean regarding whether this might be salvageable. The rust on the back is
> pretty nasty but I've seen older/worse start up just fine.
>
> - Matt G.
>
>
>
>
>

[-- Attachment #2: Type: text/html, Size: 7870 bytes --]