### RE: Cross-talk square-wave?

> The impedance of free space is supposed to be 277 Ohms 377 ohms but you are right about the max impedance. I forgot about that. > Yes, you can. The capacitance of typical cables is about 35 pF per foot. > Given a couple feet of cable and essentially infinite resistive load, it > would be

### Re: Cross-talk square-wave?

On 03/29/2017 08:48 PM, W2HX via cctalk wrote: I am still not convinced it is coupling at all. You would expect the affected line to show a signal like dV/dt , no? I just don't think you can get square waves from square waves. Yes, you can. The capacitance of typical cables is about 35 pF

### Re: Cross-talk square-wave?

> From: Eugene (W2HX) > I am still not convinced it is coupling at all. ... I just don't think > you can get square waves from square waves. ... > it is even harder to believe one could successfully couple a square > wave onto such a transmission line unless the signal is

### RE: Cross-talk square-wave?

I am still not convinced it is coupling at all. You would expect the affected line to show a signal like dV/dt , no? I just don't think you can get square waves from square waves. That's not to say the input of some logic somewhere isn't getting triggered by unintended coupling and then getting

### Re: Cross-talk square-wave?

270K is not a transmission line load. As I recall ribbon cable is around 100-150 ohms impedance some place. The signal does look nice and square. I doubt is is inductive coupling, with that high a load, I'd say it was capacitive. inductive coupling requires current flowing. Dwight

### RE: Model 28 Teletypes in Edmonton, Alberta

On Wed, 29 Mar 2017, W2HX wrote: I might have missed it, but did you offer this on the greenkeys list (or would you like me to forward it?) they are tty enthusiasts. Eugene No, I have never been a member of the green keys list and there is no point in joining now. Punt the message to the

### RE: Model 28 Teletypes in Edmonton, Alberta

I might have missed it, but did you offer this on the greenkeys list (or would you like me to forward it?) they are tty enthusiasts. Eugene -Original Message- From: cctalk [mailto:cctalk-boun...@classiccmp.org] On Behalf Of Richard Loken via cctalk Sent: Wednesday, March 29, 2017 6:42

### Model 28 Teletypes in Edmonton, Alberta

So, my ex-wife sent my Model 28 RO and Model 28 ASR (along with a Conn vacuum tube electronic organ) to the landfill yesterday. I am told by my son that they went to the Eco Station Reuse Area at either the Ambleside or kennedale Eco Station. So, in the unlikely event that somebody wanting a 28

### Re: Cross-talk square-wave?

On 3/29/17 2:14 PM, David Bridgham via cctalk wrote: > And I think this picture is the smoking gun. > > http://pdp10.froghouse.org/qsic/pic_24_2.gif > > Again, the bottom trace is the CS signal in question and the upper trace > is now one of the QBUS DAL lines (after the bus transceiver and

### Re: Cross-talk square-wave?

And I think this picture is the smoking gun. http://pdp10.froghouse.org/qsic/pic_24_2.gif Again, the bottom trace is the CS signal in question and the upper trace is now one of the QBUS DAL lines (after the bus transceiver and level converter) that's running across the ribbon cable near the CS

### Re: Cross-talk square-wave?

> There are few things that come to mind here. The op seemed to indicate the > lines are terminated. If they are not terminated in the characteristic > impedance of the source and the transmission line, it is very unlikely he > would be seeing nice square waves at either end. The reflections

### Re: Apple 1, Commodore 65, Enigma Machine, Inventor of C++

On Wed, Mar 29, 2017 at 1:29 AM, Christian Corti via cctalk < cctalk@classiccmp.org> wrote: > On Tue, 28 Mar 2017, Evan Koblentz wrote: > >> "What do an Apple 1, Commodore 65, Enigma Machine, and the inventor of >> C++ all have in common?" >> > > They're just overestimated pieces of junk ;-)

### Re: Cross-talk square-wave?

> On Mar 29, 2017, at 1:25 PM, Paul Koning via cctalk > wrote: > > ... > SD cards are not SPI, they are a variation of MMC. Sorry about that, it turns out I was working from obsolete memories. That used to be true, isn't any longer. In any case, you're dealing with

### RE: Cross-talk square-wave?

There are few things that come to mind here. The op seemed to indicate the lines are terminated. If they are not terminated in the characteristic impedance of the source and the transmission line, it is very unlikely he would be seeing nice square waves at either end. The reflections would

### Re: Cross-talk square-wave?

> 270k seems like a rather strange value, it certainly can't be a termination > and it isn't a plausible pulldown either. The SD spec should explain what is > expected; I knew it at one time but forgot by now. I'll agree that 270k is a strange value. The idea is that the SD card contains an

### Re: Cross-talk square-wave?

> 1v across 270K represents 3.7 microamps, which isn't much, particularly > at 25MHz. (I assume that you're using SPI to access the card, but the > observation still holds). Yup, I'm planning to use the SD card in SPI mode (at least for now). And this line is the CS/CD line, so it's not even

### Re: Cross-talk square-wave?

On Mar 29, 2017, at 9:40 AM, Noel Chiappa via cctalk wrote: > Hi, a question about generic analog stuff. > > In the process of getting SD cards to work, Dave is seeing square-wave noise > on a line. (1V of square wave, with pulses about 400ns long, running at > 375kHz.)

### Re: Scrounging - was Floating point routines for the 6809

On 3/28/2017 9:58 AM, Mike Stein via cctalk wrote: - Original Message - From: "Liam Proven via cctalk" To: "General Discussion: On-Topic and Off-Topic Posts" Sent: Tuesday, March 28, 2017 11:23 AM Subject: Re: Floating point routines for

### Re: Scrounging - was Floating point routines for the 6809

> On Mar 29, 2017, at 2:18 PM, Fred Cisin via cctalk > wrote: > >>> It's amazing how isolated pockets of our cultures can be from each >>> other! "Multiple peoples divided by a common language" > > On Wed, 29 Mar 2017, Chuck Guzis via cctalk wrote: > ... >> Or the time

### RE: Cross-talk square-wave?

I should mention that this is a pre-prototype; the final thing won't have a cable at all; so this isn't a fundamental issue with the design (if it is cross-talk). And the SD card isn't even plugged in when we see this - if it is cross-talk, it has to be some other signal carried in the cable.

### Re: Scrounging - was Floating point routines for the 6809

It's amazing how isolated pockets of our cultures can be from each other! "Multiple peoples divided by a common language" On Wed, 29 Mar 2017, Chuck Guzis via cctalk wrote: This is something that continually delights me, from the time that I was ridiculed by the downstate Hoosier farmers' sons

### Re: Cross-talk square-wave?

> On Mar 29, 2017, at 1:17 PM, Chuck Guzis via cctalk > wrote: > > On 03/29/2017 07:08 AM, Noel Chiappa via cctalk wrote: >>> From: Dwight Kelvey >> >>> Is there any load resistance at the end of the line? >> >> Yes, 270K to ground (i.e. pretty large). How does that

### Re: Cross-talk square-wave?

On 03/29/2017 07:08 AM, Noel Chiappa via cctalk wrote: >> From: Dwight Kelvey > >> Is there any load resistance at the end of the line? > > Yes, 270K to ground (i.e. pretty large). How does that have an effect > on whether cross-talk can create a square wave? Sorry, I'm not > understanding. 1v

### Re: Scrounging - was Floating point routines for the 6809

On Wed, Mar 29, 2017 at 6:01 PM, Chuck Guzis via cctalk wrote: > Or the time an English co-worker related the story surrounding her > initial job interval in the US. She described the stunned look on the > face of the desk clerk at the local Holiday Inn when she asked to

### Re: Scrounging - was Floating point routines for the 6809

On 03/29/2017 09:05 AM, Fred Cisin via cctalk wrote: > It's amazing how isolated pockets of our cultures can be from each > other! "Multiple peoples divided by a common language" This is something that continually delights me, from the time that I was ridiculed by the downstate Hoosier farmers'

### Re: PSU protection with resettable polyfuse

On Wed, Mar 29, 2017 at 9:24 AM, Systems Glitch via cctalk < cctalk@classiccmp.org> wrote: > > Any downsides to resettable polyfuses? > > If you hit them hard enough, they'll sometimes permanently open, which is > desirable anyway but does require rework. I don't remember how they stack > up

### Re: Scrounging - was Floating point routines for the 6809

On 29 March 2017 at 17:05, Toby Thain via cctalk wrote: But you must have overlooked the intransitive definition below: "to search about and turn up something needed from whatever source is available". I'm pretty sure that's the sense Jim was using (and it's certainly not

### Re: PSU protection with resettable polyfuse

On 29 March 2017 at 16:24, Systems Glitch wrote: > If you hit them hard enough, they'll sometimes permanently open, which is > desirable anyway but does require rework. I don't remember how they stack > up speed-wise, I'm sure it's in the datasheets. I don't mind

### Re: PSU protection with resettable polyfuse

> Any downsides to resettable polyfuses? If you hit them hard enough, they'll sometimes permanently open, which is desirable anyway but does require rework. I don't remember how they stack up speed-wise, I'm sure it's in the datasheets. Thanks, Jonathan

### Re: Scrounging - was Floating point routines for the 6809

On 29 March 2017 at 17:05, Toby Thain via cctalk wrote: > But you must have overlooked the intransitive definition below: "to search > about and turn up something needed from whatever source is available". > > I'm pretty sure that's the sense Jim was using (and it's

### PSU protection with resettable polyfuse

Hi folks, The PSU for my Executel 8085 system is an Astec AC8151-01 40W 5A unit that puts out +5/+12/-12V. A while back somone suggested using an ATX PSU in its place which TBH I'd forgotten about untl I saw a breakout board that you plug a 20 or 24 pin ATX supply into and it terminates each rail

### Re: Scrounging - was Floating point routines for the 6809

On 2017-03-29 10:50 AM, Liam Proven via cctalk wrote: On 28 March 2017 at 18:58, Mike Stein via cctalk wrote: Maybe it has a slightly different connotation on this side of the pond; I don't think it would mean "borderline theft" for most people. I did Google it first!

### Re: Scrounging - was Floating point routines for the 6809

On 28 March 2017 at 18:58, Mike Stein via cctalk wrote: > Maybe it has a slightly different connotation on this side of the pond; I > don't think it would mean "borderline theft" for most people. I did Google it first! :-) Note definition 1 here:

### Re: Cross-talk square-wave?

> From: Dwight Kelvey > Is there any load resistance at the end of the line? Yes, 270K to ground (i.e. pretty large). How does that have an effect on whether cross-talk can create a square wave? Sorry, I'm not understanding. Noel

### Re: Cross-talk square-wave?

Is there any load resistance at the end of the line? Dwight From: cctalk on behalf of Noel Chiappa via cctalk Sent: Wednesday, March 29, 2017 6:40:22 AM To: cctalk@classiccmp.org Cc:

### Cross-talk square-wave?

Hi, a question about generic analog stuff. In the process of getting SD cards to work, Dave is seeing square-wave noise on a line. (1V of square wave, with pulses about 400ns long, running at 375kHz.) The line runs through a flat cable of modest length, along with other signal-carrying lines.

### Re: Ann Arbor Ambassador XL / Re: pile of gear for sale (DEC, Sun, PC, ephemera, v.35 cables, etc etc)

I'm definitely interested in the Ann Arbor terminal - I have sent you a couple of messages but haven't heard back - I'm not sure if I have the right address? Let me know. Thanks! -Ian On Wed, Mar 29, 2017 at 1:35 AM, Andrew K. Bressen via cctalk wrote: > >> On Tue, Mar

### Re: QIX game on PDP-11

On Tue, 28 Mar 2017, Systems Glitch wrote: Looks similar to a Mentec KDJ11-B workalike, I don't remember their designation. Onboard RAM and DLV11-J from what I remember... The board says SBC J11-8, so that should give a hint. Christian

### Re: Apple 1, Commodore 65, Enigma Machine, Inventor of C++

On Tue, 28 Mar 2017, Evan Koblentz wrote: "What do an Apple 1, Commodore 65, Enigma Machine, and the inventor of C++ all have in common?" They're just overestimated pieces of junk ;-) (and C++, not its inventor) [duck...] Christian