Does anyone know what the Comparex 7/71 was?

[Chris Patti via cctalk]

http://imgur.com/a/guJlD

I just learned of its existence from this set of images of hardware
rescued from a nuclear power plant.

Is it a dumb terminal? Industrial control gear? Something else?

Thanks,
-Chris

-- 
Christopher Patti - Geek At Large | GTalk: cpa...@gmail.com | AIM:
chrisfeohpatti | P: (260) 54PATTI
"Technology challenges art, art inspires technology." - John Lasseter, Pixar

RE: DECstation 220 - Out of Ideas?

[Rob Jarratt via cctalk]

> -Original Message-
> From: cctalk [mailto:cctalk-boun...@classiccmp.org] On Behalf Of Rob Jarratt
> via cctalk
> Sent: 28 June 2017 19:12
> To: 'shad' ; 'General Discussion: On-Topic and Off-
> Topic Posts' 
> Subject: RE: DECstation 220 - Out of Ideas?
> 
> I was thinking of trying with the chip removed, so I think I will do that. I 
> have a
> multimeter of course, which is how I have been tracing already. The scanner
> idea is a good one too, and if nothing else at least it gives me an idea of 
> where
> to probe without too much flipping of the board.
> 

With the 74LS125 removed I found the ROM output enable was still not going low 
enough to enable the ROM output. Doing a bit more tracing I reached a 74LS243 
quad transceiver.

Now here I think there *is* something odd going on. I noticed that the two 
inputs GAB and GBA are both at about 1.95V. I am not sure, from my reading of 
the datasheet whether that counts as low or high, it seems to be right on the 
borderline if I am reading the datasheet correctly. The ROM OE signal is going 
to the A4 pin (pin 6) of the transceiver, so I put the scope on the B4 pin and 
it is a steady 1.4V. That behaviour does not seem to correspond to GAB and GBA 
both being high or both being low, unless what is happening is that it is 
considering GAB and GBA to be both high and it is trying to send the B signal 
to the A side, in which case two signals are sourcing to the same line and 
possibly not letting the ROM OE signal drop. Perhaps the next step would be to 
remove this transceiver (or lift A4 or B4) and see if the signal does start to 
drop correctly. At which point it is either the transceiver that is bad, or 
more likely something is telling it to do the wrong thing.

Does that seem a reasonable analysis?

Regards

Rob

Re: Help identifying UNIBUS PDP-11 CPU upgrade

[Jerry Weiss via cctalk]

> On Jun 28, 2017, at 2:35 PM, Josh Dersch via cctalk  
> wrote:
> 
> On Wed, Jun 28, 2017 at 11:02 AM, Noel Chiappa via cctalk <
> cctalk@classiccmp.org> wrote:
> 
>>> From: Josh Dersch
>> 
>>> I pulled the ... bootstrap boards from slot 3 ... The BOOT button
>>> causes the RUN light to momentarily flash, but that's about it.
>> 
>> That's not too surprising. The way booting works with the M9301 boot card
>> (not
>> sure if you know this already; if you do, apologies, and ignore) is that
>> the
>> 'BOOT' button simulates a power-fail/restart - i.e. it toggles the 'power
>> OK'
>> line (forget whether it's ACOK or DCOK). When the CPU 'powers up', and
>> tries
>> to fetch the power fail restart vector from 024/6, the M9301 steps on the
>> bus
>> address lines and modified the address to 773024/6, which is in the ROM on
>> the
>> M9301. The new PS/PC retrieved at that point then sends the CPU into the
>> ROM.
>> So, with no M9301 plugged in, it's not too surprising it doesn't do much.
>> 
> 
> Yeah, I'm aware (or at least was somewhat aware at one point...) of how
> this works.  I'm just surprised the CPU upgrade board doesn't do something
> similar to provide bootstraps, etc.
> (Or maybe it can -- there are a lot of jumpers and dip switches…)

You certainly have a nice find and congrats on getting it functional.  Is that 
an FPJ11 chip on the board as well?
It would be interesting to boot RT11 and see what the SHOW CONFIG says.   

I never came across this product in my travels.  A quick look at addresses 
north of 17773000 as you flip
the dip switches or jumpers should reveal all.  Just don’t forget were you 
parked..

Jerry 

Re: Help identifying UNIBUS PDP-11 CPU upgrade

[Josh Dersch via cctalk]

On Wed, Jun 28, 2017 at 11:02 AM, Noel Chiappa via cctalk <
cctalk@classiccmp.org> wrote:

> > From: Josh Dersch
>
> > I pulled the ... bootstrap boards from slot 3 ... The BOOT button
> > causes the RUN light to momentarily flash, but that's about it.
>
> That's not too surprising. The way booting works with the M9301 boot card
> (not
> sure if you know this already; if you do, apologies, and ignore) is that
> the
> 'BOOT' button simulates a power-fail/restart - i.e. it toggles the 'power
> OK'
> line (forget whether it's ACOK or DCOK). When the CPU 'powers up', and
> tries
> to fetch the power fail restart vector from 024/6, the M9301 steps on the
> bus
> address lines and modified the address to 773024/6, which is in the ROM on
> the
> M9301. The new PS/PC retrieved at that point then sends the CPU into the
> ROM.
> So, with no M9301 plugged in, it's not too surprising it doesn't do much.
>

Yeah, I'm aware (or at least was somewhat aware at one point...) of how
this works.  I'm just surprised the CPU upgrade board doesn't do something
similar to provide bootstraps, etc.
(Or maybe it can -- there are a lot of jumpers and dip switches...)


>
> The DEC QBUS processor cards (not sure about the chips themselves) can be
> jumpered on power-up to i) halt, or ii) fetch a PS/PC from 024/6, or iii)
> jump
> to ROM. I've no idea if this board set has something similar (and if so,
> what
> it's set to do).
>
> > Ran the front panel cable to the connector on the CPU board and
> powered
> > it up.
>
> Now I'm confused. There is no cable from the front panel to the CPU in a
> standard 11/34? (There's one from the front panel to the backplane; another
> from the front panel to the M9301; and another from the programmer's front
> panel [if present] to the programmer's front panel board, the M7859; but
> that's it, that I know of.)
>

Front panel to the CPU upgrade, not the original CPU.  If you look at the
pictures I posted, there's a pair of connectors on the CPU board that look
suspiciously like those on the M7859.  There doesn't appear to be an analog
for the M9301 cabling, however.

- Josh



>
> Did you mean the console serial line cable?
>
> Noel
>

RE: DECstation 220 - Out of Ideas?

[shadoooo via cctalk]

Hello,
now you could try to check the voltages again, just to be sure the fault is
not on the 245.

Following the traces is of course obviously difficult, but if the board is
really only two-sided (no internal signal layers), components are not too
high, and you have a flatbed scanner, you could scan both sides, then
colorize top in green and bottom in red, flip bottom and do a properly
aligned overlay with a graphic editor like GIMP.
It's a matter of few minutes, but could improve the work.
When you are unsure, try with the multimeter.

Andrea