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From: Warner Losh <>
To: segaloco <>
Cc:, The Eunuchs Hysterical Society <>
Subject: [TUHS] Re: AT&T UNIX PC (7300) Teardown and Restoration
Date: Tue, 3 Jan 2023 17:40:22 -0700	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

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


- Matt G.
> ------- Original Message -------
> On Tuesday, January 3rd, 2023 at 3:53 PM, <
>> 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 <> wrote:
> And here are some pictures of the guts.
> 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 <
>> 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.
> 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.

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  reply	other threads:[~2023-01-04  0:41 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-01-03 20:20 [TUHS] " segaloco via TUHS
2023-01-03 23:27 ` [TUHS] " segaloco via TUHS
     [not found]   ` <>
2023-01-04  0:30     ` segaloco via TUHS
2023-01-04  0:40       ` Warner Losh [this message]
2023-01-04  0:46         ` segaloco via TUHS
2023-01-04  0:57           ` Warner Losh
2023-01-04 12:39             ` Ori Idan
2023-01-04 20:48             ` Clem Cole
2023-01-04 20:53               ` Clem Cole

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