Re: 485 Cordwrap Feet

Jim Ford

Funny you should mention those IEC power connectors, Dennis, as I just received a new wired router (opting for security, reliability, and speed for my 3 computers that stay in one place) today, and what do you know, it did not have an IEC connector on it. Instead, the power cable had a "3 merged circles" (kind of like 3/5 of the Olympics symbol) connector.
Not sure why.

Now, my Tek 5103N/D10 and 7603 scopes have attached power cables, and every other piece of gear (most of it Tek or HP) I own except for the HP 400E AC voltmeter (pre-1970, no doubt) has a detachable cord with an IEC connector on it. No, wait, that's not true. I noticed some time ago that the 3 power supplies I own, an HP 6111A, an Elenco Precision XP-581, and a Trygon TL8-3, all have attached cords. I wonder why that is...

Another oddball is my Tek TLA711 mainframe. While it has an IEC male connector on the back of it, there is an extra rib below the GND pin, so a normal IEC female will not mate with it. Until you chop a groove into it with a utility knife, that is. I don't know why Tek did that. Maybe if you fill up the chassis with a thousand channels worth of logic analysis it draws so much current you need an extra beefy power cable (with a special notched IEC connector) hooked up to a 100 A circuit?

Speaking of extra beefy power cords, I have one I got from Mercury Transformers at the L.A. Guitar Amp Show some years ago. They were giving away these slick, fat, red cables. I'm not going to hook that up to just anything; no, that one is being saved for something special!
Seems like I have dozens of normal ones, though. The ones with the right angle IEC connectors come in handy when using a deep piece of equipment like a 7904 up close to the wall. But they always seem to point the wrong way, as do GPIB connectors. ;)

Rambling again - sorry.

Jim Ford

------ Original Message ------
From: "Dennis Tillman W7pF" <@Dennis_Tillman_W7pF>
Sent: 7/22/2020 11:39:48 AM
Subject: Re: [TekScopes] 485 Cordwrap Feet

Hi Jeff,
It was not unusual for the design engineers at Tek to pay attention to
product details (known as Human Factors Engineering in those days) just like
this one. This was one of the things that distinguished Tek from many other
companies. The 485 was a portable scope which meant things like a power cord
had to have a secure place to be while it was being moved from one place to
another. The logical way to carry the scope was by the handle with the scope
in an upright position so there would need to be feet on the rear of the
scope. Why not kill two birds with one stone and design a foot that would
also secure the power cord?

There are some things that the mechanical engineers at Tek never seem to be
satisfied with and cord wraps are one of them. The cord wrap evolved
constantly. It was almost as if the mechanical engineers saw each new
portable scope as an opportunity to improve on the design of the previous
instrument. My 453 (the 454 and 453 were the original portables Tek designed
to meet the needs of the IBM Field Engineers) had fairly simple rear feet
which the power cord could be wrapped around. I think there was a chance the
power cord could become undone from around the rear feet while travelling
with the 453 scope. By the time the 485 appeared the cord wrap foot was just
about optimal: It holds the power cord securely, and it communicates to the
user, by its unusual shape, what its intended purpose is, without the need
for any further explanation.

In other words its unusual shape tells you what it does. Donald Norman in
his book "The Psychology of Everyday Things" coined the term "affordances"
for the properties of objects which show users the actions they can take.
Users should be able to perceive affordances without having to consider how
to use the items. A simple example we all encounter every day is the handle
on a door leading into or out of a store. The shape of the handle should
communicate to you whether you should push or pull it to open the door.
Instead most of them are so poorly designed that it is necessary to include
a sign saying "Push" or "Pull".

With the advent of the IEC power connector standard in 1970 many instruments
gradually started using power cords that could be unplugged from the
instrument which created a totally different problem of what to do with the
proliferation of these power cords now that they are everywhere. Somehow we
all end up with more of them than we can possibly use.

Dennis Tillman W7pF

-----Original Message-----
From: [] On Behalf Of Jeff
Sent: Tuesday, July 21, 2020 12:30 PM
Subject: [TekScopes] 485 Cordwrap Feet

I had a customer approach me about developing a replacement cord wrap foot
for the Tektronix 485. He sent me one of his that was mostly intact - but it
led to some questions that I'm now posing to the group.

The 485 service manual shows that the cord wrap looks a lot like the cord
wraps on a 2465, i.e. two assemblies, one right side and one left side, that
extend from the bottom to the top, and the cord wraps around the two of

On the other hand, what my customer sent to me looked more like a foot from
a 465, i.e. 4 pieces, one on each corner, with flanges to hold the cord. The
cord wraps around the four pieces located at each corner.

Did early and later versions of the 485 have different cord wraps? If so,
are they interchangeable? I can only find one version of the service manual,
and it shows the 2465-like cord wraps.

Would greatly appreciate anyone who could shed light on this mystery.

Jeff / N0DY

Dennis Tillman W7pF
TekScopes Moderator

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