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

[Warner Losh <imp@bsdimp.com>]

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https://www.amazon.com/NOYITO-Module-Conversion-Arduino-communicates/dp/B07BJJ1T5G

is my go-to for when I need a simple one, though something like

https://www.amazon.com/NOYITO-Module-Conversion-Arduino-communicates/dp/B07BJJ3TZR

might work better for your setup if you just have more of the TTL gear than
RS-232 gear (I have way too many old RS-232 cables because I never know
when I'll need them again...)

Warner

On Tue, Jan 3, 2023 at 5:46 PM segaloco <segaloco@protonmail.com> wrote:

> Nope, unfortunately I only know as much as is needed to plug into the GPIO
> RX/TX/GND working on single boards. I wouldn't be surprised if my
> assumption I just run these pins into the D-25 in the right holes is
> bunk...but that's how we learn sometimes. Once I move I should be able to
> setup a proper work bench where I can tinker on this sort of thing more
> intentionally rather than haphazardly. So perhaps a silly question for an
> expert but a valid one for me. I'll chase that angle and see if it bears
> fruit.
>
> - Matt G.
> ------- Original Message -------
> On Tuesday, January 3rd, 2023 at 4:40 PM, Warner Losh <imp@bsdimp.com>
> wrote:
>
>
>
> 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.
>>
>>
>>
>>
>>
>

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