It's amazing what you can get away with
 

Thirty-two years ago I made a little unit that switched a couple of CCTV
feeds and a floodlight. It was controlled by a 'normally on' 12V feed
from a sensor which controlled a 12V relay that in turn controlled three
timer relays. Two switched the video, which went to a monitor. The third
switched a floodlight. At the time I was surprised that ordinary relays
could pass baseband video with no apparent ill effects. But anyway, last
week, after all those years, it was decided that a manual over-ride of
the floodlight switching would be useful. The diecast box was opened for
the first time since installation and I peered inside. All the external
connections were via a long 'choc block' strip, and just above that was
a card with the connection details on it. These details were obscured by
the cables, so I gently bent one cable with the tip of a screwdriver. At
this the relays clicked and the timing sequences started. I drew back my
screwdriver in surprise. It turned out that the screw in the choc block
for one of the two sensor leads had never been tightened, and contact
was hit and miss. This piece of kit has functioned faultlessly since 1982.

Bill

It's amazing what you can get away with
 

Bill Wright wrote:

These details were obscured by the cables, so I gently bent one cable
with the tip of a screwdriver. At this the relays clicked and the timing
sequences started. I drew back my screwdriver in surprise. It turned out
that the screw in the choc block for one of the two sensor leads had
never been tightened, and contact was hit and miss. This piece of kit has
functioned faultlessly since 1982.

Hi Bill

I had a very similar experience with one of our first machines built in
1991. It had worked faultlessly up until last year. There was no obvious
failure so I removed a terminal box lid and a wire fell out! Amazingly
there was no sign of overheating or arcing even though the wire was
carrying 230v at up to 5A. Judging from the depth of dust and cobwebs I
discounted 'fiddling'.

Barry

It's amazing what you can get away with
 

Bill, it shows that even when a screw is bad it's still pretty good!

"Bill Wright" wrote in message
...
screwdriver in surprise. It turned out that the screw in the choc block
for one of the two sensor leads had never been tightened, and contact was
hit and miss. This piece of kit has functioned faultlessly since 1982.

Bill



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It's amazing what you can get away with
 

Yes, I built a dark sensor on a bit of blob board back in the 70s as a
temporary job, I put it into a box using double sided tape, and it was there
from 76 to 2011, with no issues. The light sensor was an ORP12 a devider
network on the front of a simple Schmidt trigetr using out of spec
transistors withe an old relay and the psu was also built very simply.
The only thing that was really wrong with it when I took it down was dried
out electrolytics causing dodgy switching due to hum on the supply.

a friend could have fixed it. Oh and some creature had set up home inside,
looked like a spider.

Its that old adage once again. If it aint broke, don't fix it.
Of course I could not have built it now. I was amazed that the douuble
sided tape and the way I'd blobbed it all together survived all that time.
One might call it early surface mount.. grin.
Brian

--
From the Sofa of Brian Gaff Reply address is active
"Bill Wright" wrote in message
...
Thirty-two years ago I made a little unit that switched a couple of CCTV
feeds and a floodlight. It was controlled by a 'normally on' 12V feed from
a sensor which controlled a 12V relay that in turn controlled three timer
relays. Two switched the video, which went to a monitor. The third
switched a floodlight. At the time I was surprised that ordinary relays
could pass baseband video with no apparent ill effects. But anyway, last
week, after all those years, it was decided that a manual over-ride of the
floodlight switching would be useful. The diecast box was opened for the
first time since installation and I peered inside. All the external
connections were via a long 'choc block' strip, and just above that was a
card with the connection details on it. These details were obscured by the
cables, so I gently bent one cable with the tip of a screwdriver. At this
the relays clicked and the timing sequences started. I drew back my
screwdriver in surprise. It turned out that the screw in the choc block
for one of the two sensor leads had never been tightened, and contact was
hit and miss. This piece of kit has functioned faultlessly since 1982.

Bill

It's amazing what you can get away with
 

I blame the vibrations...

Brian

--
From the Sofa of Brian Gaff Reply address is active
"Y Dangle" wrote in message
...
Bill, it shows that even when a screw is bad it's still pretty good!

"Bill Wright" wrote in message
...
screwdriver in surprise. It turned out that the screw in the choc block
for one of the two sensor leads had never been tightened, and contact was
hit and miss. This piece of kit has functioned faultlessly since 1982.

Bill



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It's amazing what you can get away with
 

On 5 Feb 2014 08:14:18 GMT, Barry wrote:

Bill Wright wrote:

These details were obscured by the cables, so I gently bent one cable
with the tip of a screwdriver. At this the relays clicked and the timing
sequences started. I drew back my screwdriver in surprise. It turned out
that the screw in the choc block for one of the two sensor leads had
never been tightened, and contact was hit and miss. This piece of kit has
functioned faultlessly since 1982.

Hi Bill

I had a very similar experience with one of our first machines built in
1991. It had worked faultlessly up until last year. There was no obvious
failure so I removed a terminal box lid and a wire fell out! Amazingly
there was no sign of overheating or arcing even though the wire was
carrying 230v at up to 5A. Judging from the depth of dust and cobwebs I
discounted 'fiddling'.

A little different but this reminds me one time an OR engineer came
out to look at an ADSL speed issue. He found a complete break in my
phone line, fixed it. Afterwards the ADSL speed was completely
unchanged.
--
(\__/) M.
(='.'=) If a man stands in a forest and no woman is around
(")_(") is he still wrong?

It's amazing what you can get away with
 

In article ,
Bill Wright writes:
It turned out that the screw in the choc block for one of the two
sensor leads had never been tightened, and contact was hit and
miss. This piece of kit has functioned faultlessly since 1982.

So it seems that the contact must have been almost entirely "hit". :)
--
John Hall "He crams with cans of poisoned meat
The subjects of the King,
And when they die by thousands G.K.Chesterton:
Why, he laughs like anything." from "Song Against Grocers"

It's amazing what you can get away with
 

If it was a two screw one, ie the other side has a screw as well, then it
might have been holding on via this until it was disturbed. Just as well
there are no earthquakes in the north of England, at least not until the
fracing has started.
Brian

--
From the Sofa of Brian Gaff Reply address is active
"John Hall" wrote in message
...
In article ,
Bill Wright writes:
It turned out that the screw in the choc block for one of the two
sensor leads had never been tightened, and contact was hit and
miss. This piece of kit has functioned faultlessly since 1982.

So it seems that the contact must have been almost entirely "hit". :)
--
John Hall "He crams with cans of poisoned meat
The subjects of the King,
And when they die by thousands G.K.Chesterton:
Why, he laughs like anything." from "Song Against Grocers"

It's amazing what you can get away with
 

Barry wrote:
Bill Wright wrote:

These details were obscured by the cables, so I gently bent one cable
with the tip of a screwdriver. At this the relays clicked and the timing
sequences started. I drew back my screwdriver in surprise. It turned out
that the screw in the choc block for one of the two sensor leads had
never been tightened, and contact was hit and miss. This piece of kit has
functioned faultlessly since 1982.

Hi Bill

I had a very similar experience with one of our first machines built in
1991. It had worked faultlessly up until last year. There was no obvious
failure so I removed a terminal box lid and a wire fell out! Amazingly
there was no sign of overheating or arcing even though the wire was
carrying 230v at up to 5A. Judging from the depth of dust and cobwebs I
discounted 'fiddling'.

Ha! By the way we are still selling those washers, 50 at a time!

Bill

It's amazing what you can get away with
 

Brian_Gaff wrote:
If it was a two screw one, ie the other side has a screw as well, then it
might have been holding on via this until it was disturbed. Just as well
there are no earthquakes in the north of England, at least not until the
fracing has started.
Brian

No the other screw wasn't involved. The bit of bare wire that came out
of the choc block had been folded to make it thicker but was very short.

Bill

It's amazing what you can get away with
 

On Wed, 05 Feb 2014 10:13:00 +0000, Mark
wrote:

A little different but this reminds me one time an OR engineer came
out to look at an ADSL speed issue. He found a complete break in my
phone line, fixed it. Afterwards the ADSL speed was completely
unchanged.

Implying there might be another break (or other fault) somewhere else...

It's amazing what you can get away with
 

Was it one of those posh blocks with the metal sprung strip inside to press
on the wire instead of the end of the screw?

Brian

--
From the Sofa of Brian Gaff Reply address is active
"Bill Wright" wrote in message
...
Brian_Gaff wrote:
If it was a two screw one, ie the other side has a screw as well, then it
might have been holding on via this until it was disturbed. Just as well
there are no earthquakes in the north of England, at least not until the
fracing has started.
Brian

No the other screw wasn't involved. The bit of bare wire that came out of
the choc block had been folded to make it thicker but was very short.

Bill

It's amazing what you can get away with
 

Mark wrote:

A little different but this reminds me one time an OR engineer came
out to look at an ADSL speed issue. He found a complete break in my
phone line, fixed it. Afterwards the ADSL speed was completely
unchanged.

We at the BT research place expected ADSL to be rather fragile in the
face of line faults. Unexplained poor performance was often blamed on
things like aluminium conductors, a particular type of crimp, and other
"bonnet bees" of various types.

As time went by, one thing became clearer: ADSL is often more resilient
to line faults than the telephony service running on the same wires.
In particular, high resistance and disconnect faults often left the
ADSL working whilst the telephony was unbearably noisy or non-existent.
There's enough capacitance to allow the ADSL frequencies to be carried
even across a disconnect.

Having said that, ADSL doesn't seem at all happy with "battery-" or
"earth-contact" faults (which cause an audible mains hum on the line
due to unbalancing it. Unbalancing seems to have the biggest effect,
which is probably what you'd expect.

--
SteveT

It's amazing what you can get away with
 

"Steve Thackery" wrote in message
...
Mark wrote:

A little different but this reminds me one time an OR engineer came
out to look at an ADSL speed issue. He found a complete break in my
phone line, fixed it. Afterwards the ADSL speed was completely
unchanged.

We at the BT research place expected ADSL to be rather fragile in the
face of line faults. Unexplained poor performance was often blamed on
things like aluminium conductors, a particular type of crimp, and other
"bonnet bees" of various types.

As time went by, one thing became clearer: ADSL is often more resilient
to line faults than the telephony service running on the same wires.
In particular, high resistance and disconnect faults often left the
ADSL working whilst the telephony was unbearably noisy or non-existent.
There's enough capacitance to allow the ADSL frequencies to be carried
even across a disconnect.

Having said that, ADSL doesn't seem at all happy with "battery-" or
"earth-contact" faults (which cause an audible mains hum on the line
due to unbalancing it. Unbalancing seems to have the biggest effect,
which is probably what you'd expect.

--
SteveT

ADSL does amazingly well over miles of very thin, often corroded and / or
half submerged aluminium conductor, with connections that would make a
school boy cringe. Ten megabits+ per second with negligible BERR rates.

Then you pick up a copy some hi-brow hi-fi magazine that tells you that for
decent audio quality (~100kbps) you need solid silver cables with gold
plated connectors costing £££ to reliably transfer data just a meter or
so....

OTOH it could be humm from the mains...

From Hi-Fi Choice

Isol- 8 Powerline Axis Mains Filter- £499
Mains filtration removes high-frequency noise, but as Richard Black
discovers Isol-8's Powerline Axis goes the other way, removing direct
current



Fortunately my hi-fi has a big transformer (filtering out HF noise) and lots
of big capacitors in the power supply (smoothing out the LF noise), so it is
so quiet [with no input] that I sometimes forget to switch it off when I go
to bed...

It's amazing what you can get away with
 

"R. Mark Clayton" wrote in
message ...

"Steve Thackery" wrote in message
...
Mark wrote:

A little different but this reminds me one time an OR
engineer came
out to look at an ADSL speed issue. He found a complete
break in my
phone line, fixed it. Afterwards the ADSL speed was
completely
unchanged.

We at the BT research place expected ADSL to be rather
fragile in the
face of line faults. Unexplained poor performance was
often blamed on
things like aluminium conductors, a particular type of
crimp, and other
"bonnet bees" of various types.

As time went by, one thing became clearer: ADSL is often
more resilient
to line faults than the telephony service running on the
same wires.
In particular, high resistance and disconnect faults
often left the
ADSL working whilst the telephony was unbearably noisy or
non-existent.
There's enough capacitance to allow the ADSL frequencies
to be carried
even across a disconnect.

Having said that, ADSL doesn't seem at all happy with
"battery-" or
"earth-contact" faults (which cause an audible mains hum
on the line
due to unbalancing it. Unbalancing seems to have the
biggest effect,
which is probably what you'd expect.

--
SteveT

ADSL does amazingly well over miles of very thin, often
corroded and / or half submerged aluminium conductor, with
connections that would make a school boy cringe. Ten
megabits+ per second with negligible BERR rates.

Then you pick up a copy some hi-brow hi-fi magazine that
tells you that for decent audio quality (~100kbps) you
need solid silver cables with gold plated connectors
costing £££ to reliably transfer data just a meter or
so....

OTOH it could be humm from the mains...

From Hi-Fi Choice

Isol- 8 Powerline Axis Mains Filter- £499
Mains filtration removes high-frequency noise, but as
Richard Black discovers Isol-8's Powerline Axis goes the
other way, removing direct current



Fortunately my hi-fi has a big transformer (filtering out
HF noise) and lots of big capacitors in the power supply
(smoothing out the LF noise), so it is so quiet [with no
input] that I sometimes forget to switch it off when I go
to bed...




Ah, you're not a disciple of Rip-off Russ then?


--
Woody

harrogate three at ntlworld dot com

It's amazing what you can get away with
 

Brian_Gaff wrote:
Was it one of those posh blocks with the metal sprung strip inside to press
on the wire instead of the end of the screw?

Brian

Could have been. I use those now, but dunno about 30-odd years ago.
They're good though, in my opinion.

Bill

It's amazing what you can get away with
 

Steve Thackery wrote:

As time went by, one thing became clearer: ADSL is often more resilient
to line faults than the telephony service running on the same wires.
In particular, high resistance and disconnect faults often left the
ADSL working whilst the telephony was unbearably noisy or non-existent.
There's enough capacitance to allow the ADSL frequencies to be carried
even across a disconnect.

This reminds me of the early days of UHF TV. With VHF a broken inner
core in the downlead would result in zero reception. With UHF (ch51
here) the signal level would drop dramatically, but usually there's
still be a picture and sound.

Bill

It's amazing what you can get away with
 

R. Mark Clayton wrote:

Fortunately my hi-fi has a big transformer (filtering out HF noise) and lots
of big capacitors in the power supply (smoothing out the LF noise), so it is
so quiet [with no input] that I sometimes forget to switch it off when I go
to bed...

I don't switch mine off!

Bill

It's amazing what you can get away with
 

Bill Wright wrote:

Ha! By the way we are still selling those washers, 50 at a time!

Well, just let me know when you need some more. They'll be laser cut this
time.

Best regards
Barry

It's amazing what you can get away with
 

Barry wrote:
Bill Wright wrote:

Ha! By the way we are still selling those washers, 50 at a time!

Well, just let me know when you need some more. They'll be laser cut this
time.

Best regards
Barry

Ah, that's good. They have been a invaluable. You should be pleased that
you have helped a whole lot of murderers, rapists, child molesters, and
terrorists to get good TV reception...

Bill

It's amazing what you can get away with
 

Yes they don't break off the wire as you tighten it.
Brian

--
From the Sofa of Brian Gaff Reply address is active
"Bill Wright" wrote in message
...
Brian_Gaff wrote:
Was it one of those posh blocks with the metal sprung strip inside to
press on the wire instead of the end of the screw?

Brian

Could have been. I use those now, but dunno about 30-odd years ago.
They're good though, in my opinion.

Bill

It's amazing what you can get away with
 

Brian_Gaff wrote:
Yes they don't break off the wire as you tighten it.
Brian


I had a batch of the ones without the metal 'tongue' and they cut the
wire even before you'd really tightened them. The screws had circular,
sharp, 'flash' around the bottom.

Quality, eh?

Bill

It's amazing what you can get away with
 

On Thu, 06 Feb 2014 11:44:03 +0000, Bill Wright
wrote:

Brian_Gaff wrote:
Yes they don't break off the wire as you tighten it.
Brian


I had a batch of the ones without the metal 'tongue' and they cut the
wire even before you'd really tightened them. The screws had circular,
sharp, 'flash' around the bottom.

Quality, eh?


I think the idea was to 'spread the effect' of cold welding. The big
flaw was that it was all too easy to overdo it (plus there was no
'spring applied pressure' that would maintain the contact pressure
through thermal cycling).
--
Regards, J B Good

It's amazing what you can get away with
 

Johny B Good wrote:

I think the idea was to 'spread the effect' of cold welding. The big
flaw was that it was all too easy to overdo it (plus there was no
'spring applied pressure' that would maintain the contact pressure
through thermal cycling).

These ones I had were unusable. Any reasonable tightening would start to
cut the wire, then if you moved it strands would pop out.

Bill

It's amazing what you can get away with
 

Johny B Good wrote:

I think the idea was to 'spread the effect' of cold welding.

Yes, I'm familiar with those, but I don't agree: you are being too
generous! I'm almost certain there was no "idea" to it, merely crap
manufacturing.

--
SteveT