3 Jan
2007
3 Jan
'07
1:33 p.m.
Anyone know where D-shell connectors first appeared on equipment?
Interesting thread going on in a local group at the moment about why SCART [1]
sockets are so horrible and nasty (prone to breaking pins, difficult to line
up, prone to falling out etc.) and why something better, like a D-shell
connector, wasn't chosen instead.
Thing is, SCART was apparently first used in consumer A/V equipment in 1977,
which probably means it was thought up in the mid-70's. Edge connectors and/or
circular DIN connectors were probably more common on computer equipment of
that time, but were D-shell types around by then too?
[1] For the non-Europeans, SCART is common on all A/V equipment in Europe and
provides component RGB (as well as composite) interconnect between devices,
along with stereo audio channels, sync lines, remote device standby control etc.
cheers
Jules
3 Jan
3 Jan
2:08 p.m.
On 3/1/07 21:33, "Jules Richardson" <julesrichardsonuk at yahoo.co.uk>
wrote:
Anyone know where D-shell connectors first appeared on equipment?
Interesting thread going on in a local group at the moment about why SCART [1]
sockets are so horrible and nasty (prone to breaking pins, difficult to line
up, prone to falling out etc.) and why something better, like a D-shell
connector, wasn't chosen instead.
SCART was originally known as PERITEL and originated in France.
Make of that what you will :)
--
Adrian/Witchy
Binary Dinosaurs creator/curator
Www.binarydinosaurs.co.uk - the UK's biggest private home computer
collection?
3:07 p.m.
Adrian Graham wrote:
On 3/1/07 21:33, "Jules Richardson"
<julesrichardsonuk at yahoo.co.uk> wrote:
To be honest, it's a great idea - and much better than non-European countries
where the typical connectivity is via RF only.
Going source->modulator->tuner->display never did seem like a good idea when
you could just go source->display via separate shielded RGB signals. (The
picture quality I've seen on the typical US setup is piss-poor compared to the
UK, jokes about NTSC aside)
It's just a shame that the connector they picked for the standard is so lousy.
Having looked at some old pricelists, SCART connectors weren't much cheaper
than D-shells - and given that they were typically used on expensive equipment
which only contained a couple of them, the difference couldn't have been
significant at all.
The only thing I can think of (other than it being some odd political
decision) is that you know SCART is SCART; if using D-shells there would have
been a few idiots trying to plug any old computer cable into their equipment.
That hardly seems justification to enforce a nasty connector choice, though.
Assuming that D-shell connectors were around, of course - but if Chuck's right
then they should have been readily available in the mid-70's. Pin spacing is
wider on SCART, so presumably they suffer less from interference - but we all
know that D-shells are perfectly good for video (particularly at TV rates).
cheers
Jules
Anyone know where D-shell connectors first
appeared on equipment?
Interesting thread going on in a local group at the moment about why SCART [1]
sockets are so horrible and nasty (prone to breaking pins, difficult to line
up, prone to falling out etc.) and why something better, like a D-shell
connector, wasn't chosen instead.
SCART was originally known as PERITEL and originated in France.
Make of that what you will :) 
3:45 p.m.
Wikipedia claims they were invented by ITT Canon, but doesn't give a year.
<http://en.wikipedia.org/wiki/DB-25>
--
"The Direct3D Graphics Pipeline" -- DirectX 9 draft available for download
<http://www.xmission.com/~legalize/book/download/index.html>
Legalize Adulthood! <http://blogs.xmission.com/legalize/>
3:52 p.m.
On 3/1/07 23:07, "Jules Richardson" <julesrichardsonuk at yahoo.co.uk>
wrote:
UK, jokes about NTSC aside)
Never The Same Colour? :)
The only thing I can think of (other than it being
some odd political
decision) is that you know SCART is SCART; if using D-shells there would have
Yes the connector is the same, but the wiring suffers the same faults as
D(b)25, you can't pick up a SCART and assume it'll do what you want, also
you can't even assume that because there's a thick cable between connectors
then there's a full set of connections in each plug....
--
Adrian/Witchy
Binary Dinosaurs creator/curator
Www.binarydinosaurs.co.uk - the UK's biggest private home computer
collection?
4 Jan
4 Jan
3:56 p.m.
To be honest, it's a great idea - and much better
than non-European countries
where the typical connectivity is via RF only.
Going source->modulator->tuner->display never did seem like a good idea when
you could just go source->display via separate shielded RGB signals. (The
picture quality I've seen on the typical US setup is piss-poor compared to the
UK, jokes about NTSC aside)
One reason for this, I susepct, is that before the common usage of SMPSUs
in TV sets, almost all TVs were live-chassis, with all the internal
circuitry directly connected to the mains. Very few UK/European sets had
an isoalting mains transdormer.
It;s is a lot easier to isolate a VHF or UHF signal (a couple of special
capacitors will do it) than baseband video/audio (which would involve
spectial transformers or opto-isolators at least). I've seen a few
top-end (B&) and the like) valved TVs (live chassis, of ocurse) which had
a special audio transformer to provide an isolated (from the mains) audio
output from the set to feed into a tape recorder or whatever. But it
wasn't common at all.
-tony
12:36 p.m.
It;s is a lot easier to isolate a VHF or UHF signal (a couple of special
capacitors will do it) than baseband video/audio (which would involve
spectial transformers or opto-isolators at least). I've seen a few
top-end (B&) and the like) valved TVs (live chassis, of ocurse) which had
a special audio transformer to provide an isolated (from the mains) audio
output from the set to feed into a tape recorder or whatever. But it
wasn't common at all.
-tony
Very common here also (chassis live) till mid 1990's then changed to
isolation via the flyback transformer, partial hot chassis till
flyback transformer. Then SMPS for isolation. Some do double
isolation via SMPS then flyback transformer.
Still, certain area of chassis (just a one board now) even on SMPS is
hot.
Isolation transformer is a MUST when servicing any even brand new
set. No buts or ifs.
Cheers, Wizard
5 Jan
5 Jan
11:12 a.m.
Very common here also (chassis live) till mid
1990's then changed to
isolation via the flyback transformer, partial hot chassis till
Interesting. There were sets over here (made by a company called Salora,
I think) that had what was commanly known as the IPSALO circuit. That was
an acronym for 'Integrated Power Supply and Line Output' (Line Output
being what we call the Horizontal Output stage). IIRC, the horizontal
yoke was on the live side of the power supply, the vertical yoke (and in
fact the entire vertical deflection circuit) was on the isolated side. Hmmm..
flyback transformer. Then SMPS for isolation. Some
do double
isolation via SMPS then flyback transformer.
Never seen that,
Still, certain area of chassis (just a one board now) even on SMPS is
hot.
Sure.
Isolation transformer is a MUST when servicing any even brand new
set. No buts or ifs.
And, indeed, for working on any SMPSU (which are common in classic
computers, and therefore on-topic).
I think I've mentioend the origianl Tandy Model 1 monitor before, but
it's worth doing so again. it was based (as is well-known) on an RCA
protable TV, the tuner and IF boards were removed and the latter replaced
by a composite video input board. That TV was live chassis. US versions
have a on opto-isolater on the video input board (that's the reason for
the 5V power output on the model 1's video DIN socket, to power the input
side of the opto-isolator circuit), every thing else inide the monitor is
live!. European models have a step-down _isolating_ transformer inside
the case (since the TV chassis was designed for 115V mains input only),
the video input board is then little more than a transistor buffer stage.
Of course with that version almost all the circuitry inside the monitor
is isolated from the power line.
But be _very_ careful if you work on the US version!
-tony
3 Jan
3 Jan
2:14 p.m.
On 3 Jan 2007 at 15:33, Jules Richardson wrote:
Thing is, SCART was apparently first used in consumer
A/V equipment in 1977,
which probably means it was thought up in the mid-70's. Edge connectors and/or
circular DIN connectors were probably more common on computer equipment of
that time, but were D-shell types around by then too?
If my memory isn't too faulty, DB25's (used to be called "Cannon
connectors") go back at least to the early 60s. Ma Bell used them on
her datacomm equipment, complete with the chunky bakelite hoods.
Cheers,
Chuck
2:56 p.m.
Anyone know where D-shell connectors first appeared on equipment?
Earlier than you might think. I would guess 1950's/early 1960s. I've got
bits of navigational equipment, stuffed full of valves, and they have D
connectors on the modules.
They were certainly around long before the horrible SCART plug!
Interesting thread going on in a local group at the moment about why SCART [1]
sockets are so horrible and nasty (prone to breaking pins, difficult to line
up, prone to falling out etc.) and why something better, like a D-shell
connector, wasn't chosen instead.
Well, the D connector is not really an RF connector (yes, there are
versions with coaxial connector inserts, when did those come out?). Mind
you, the SCART connecotr is not exactly constnat impedance either!
Thing is, SCART was apparently first used in consumer A/V equipment in 1977,
which probably means it was thought up in the mid-70's. Edge connectors and/or
circular DIN connectors were probably more common on computer equipment of
that time, but were D-shell types around by then too?
Well, for home comuputers, maybe (the DIN connector [1], another horrible
thing, beaten only by the mini-DIN IMHO, was not at all common on larger
machines . But the DB25 was already well-established for RS232 serial
connections at that point.
[1] I don't know the date of that either, but Philips had DIN connectors
on tape recoerders in the mid 1960s.
[An aside. Am I the only person here to rememebr the IEC record player
connector? It's a flat thing with 5 flat pins on 0.2" (IIRC) centres, no
overal shroud round the pins like a DIN plug. The pins are arranged
something like :
-- -- | -- |
Every other pin is ground, the other 2 are left and right audio inputs.
Oh yes, the pins are called P, Q, R, S, T for some totally unknown reason.
A couple of my old Philps tape recorders have such a socket on them for
the record player input (wired in parallel with a DIN socket,
thankfully!). I have also found _one_ plug in my overstocked junk box. No
idea where you'd get more of them now. ]
-tony
3:24 p.m.
Tony Duell wrote:
I was struggling to think of any - but then most of the systems we have are
either 50's / 60's (and tend to use all manner of oddball connectors), or are
late-70's onwards (and so post-date SCART). There seems to be a real blank
spot when it comes to early 70's systems, for some reason. (I'm not at all
clued up on our DEC stuff though, so some of that may well qualify)
Well, the D connector is not really an RF connector
(yes, there are
versions with coaxial connector inserts, when did those come out?). Mind
you, the SCART connecotr is not exactly constnat impedance either!
Indeed; I can't see why a D-type would be any worse, and it would have
eliminated a lot of the problems with SCART types.
Thing is,
SCART was apparently first used in consumer A/V equipment in 1977,
which probably means it was thought up in the mid-70's. Edge connectors and/or
circular DIN connectors were probably more common on computer equipment of
that time, but were D-shell types around by then too?
Well, for home comuputers, maybe (the DIN connector [1], another horrible
thing, beaten only by the mini-DIN IMHO, was not at all common on larger
machines . But the DB25 was already well-established for RS232 serial
connections at that point. [An aside. Am I the only person here to rememebr the
IEC record player
connector? It's a flat thing with 5 flat pins on 0.2" (IIRC) centres, no
overal shroud round the pins like a DIN plug. The pins are arranged
something like :
-- -- | -- |
Every other pin is ground, the other 2 are left and right audio inputs.
Hmm, I've seen those about - I think I've still got one in the junk box
somewhere, although I don't recall what gadget it came from.
cheers
Jules
3:47 p.m.
On 3/1/07 22:56, "Tony Duell" <ard at p850ug1.demon.co.uk> wrote:
A couple of my old Philps tape recorders have such a
socket on them for
the record player input (wired in parallel with a DIN socket,
thankfully!). I have also found _one_ plug in my overstocked junk box. No
idea where you'd get more of them now. ]
I remember my parents having a Sharp amp plus Garrard record deck back in
the 70s that had similar connections for the speakers, but that's a bit OT
:)
As an aside I was there over xmas and they still have the same setup in a
box somewhere, bits of me are thinking I should keep it for the
forseeable....
--
Adrian/Witchy
Binary Dinosaurs creator/curator
Www.binarydinosaurs.co.uk - the UK's biggest private home computer
collection?
4 Jan
4 Jan
4:04 p.m.
I remember my parents having a Sharp amp plus Garrard
record deck back in
the 70s that had similar connections for the speakers, but that's a bit OT
:)
Are you sure you're not thinking of the 2 pin DIN speaker connector which
has one flat pin in the centre of the (cylinderical) plug and a round pin
alongside it? Very common...
I believe, BTW, there's also a 2 pin DIN plug of the normal type (overall
cylindtical mertal chell, all round pins). It has a plastic
switch-operating peg too. It was used on a frw portable tape recorders
for ecternal; PSU/removte control.
-tony
6:55 p.m.
At one time, I owned a Roberts/Akai reel-to-reel tape deck
(valve/tube model) in the 60's with a 5-pin DIN input connector. It
was years before I figured out what it was, as it wasn't labeled.
"Regular" input was via quarter-inch mono phone jacks.
Cheers,
Chuck
5 Jan
5 Jan
12:47 a.m.
On 5/1/07 00:04, "Tony Duell" <ard at p850ug1.demon.co.uk> wrote:
Ah, that's the one....
--
Adrian/Witchy
Binary Dinosaurs creator/curator
Www.binarydinosaurs.co.uk - the UK's biggest private home computer
collection?
I remember my
parents having a Sharp amp plus Garrard record deck back in
the 70s that had similar connections for the speakers, but that's a bit OT
:)
Are you sure you're not thinking of the 2 pin DIN speaker connector which
has one flat pin in the centre of the (cylinderical) plug and a round pin
alongside it? Very common... 
3 Jan
3 Jan
5:01 p.m.
On Wed, 3 Jan 2007, Tony Duell wrote:
Well, for home comuputers, maybe (the DIN connector
[1], another horrible
thing, beaten only by the mini-DIN IMHO, was not at all common on larger
machines . But the DB25 was already well-established for RS232 serial
connections at that point.
[1] I don't know the date of that either, but Philips had DIN connectors
on tape recoerders in the mid 1960s.
My father had a Telefunken "High Fi" from the 50s that had some DINs.
--
Grumpy Ol' Fred cisin at xenosoft.com
6565
days inactive
6567
days old
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