I've been looking at a Smith's revcounter from the '80s which has an
unusual (to me) PCB. The visible components are all standard - not surface
mount - but there are resistors and small caps which appear to be part of
the conductive layer. Not the usual surface mount stuff.

The actual board is some form of white plastic. There appear to be three
layers on the surface. Coloured light green, which covers most of the
board, a darker green which is the tracks and a deep green/black for the
resistors, etc.

Anyone throw some light on the technology? I'll put a link to a pic if
needed.

--
*The statement below is true.

Dave Plowman London SW
To e-mail, change noise into sound.

Dave Plowman (News) wrote:
I've been looking at a Smith's revcounter from the '80s which has an
unusual (to me) PCB. The visible components are all standard - not surface
mount - but there are resistors and small caps which appear to be part of
the conductive layer. Not the usual surface mount stuff.

The actual board is some form of white plastic. There appear to be three
layers on the surface. Coloured light green, which covers most of the
board, a darker green which is the tracks and a deep green/black for the
resistors, etc.

Anyone throw some light on the technology? I'll put a link to a pic if
needed.

Sounds a bit like thick film hybrid technology. Resistors were printed
with resistive ink and then if needed laser trimmed.

Bob

"Dave Plowman (News)" wrote in message
...
I've been looking at a Smith's revcounter from the '80s which has an
unusual (to me) PCB. The visible components are all standard - not
surface
mount - but there are resistors and small caps which appear to be
part of
the conductive layer. Not the usual surface mount stuff.

The actual board is some form of white plastic. There appear to be
three
layers on the surface. Coloured light green, which covers most of
the
board, a darker green which is the tracks and a deep green/black for
the
resistors, etc.

Anyone throw some light on the technology? I'll put a link to a pic
if
needed.

--
*The statement below is true.

Dave Plowman London SW
To e-mail, change noise into sound.

There were 'printed resistors' which were laid down with a silk
screen, so I suppose there could have been printed capacitors, but I
would imagine the values would be small.

AWEM

Dave Plowman (News) wrote:

I've been looking at a Smith's revcounter from the '80s which has an
unusual (to me) PCB. The visible components are all standard - not surface
mount - but there are resistors and small caps which appear to be part of
the conductive layer. Not the usual surface mount stuff.

Thick film hybrid circuits?

In article ,
Bob Minchin wrote:
Dave Plowman (News) wrote:
I've been looking at a Smith's revcounter from the '80s which has an
unusual (to me) PCB. The visible components are all standard - not
surface mount - but there are resistors and small caps which appear to
be part of the conductive layer. Not the usual surface mount stuff.

The actual board is some form of white plastic. There appear to be
three layers on the surface. Coloured light green, which covers most
of the board, a darker green which is the tracks and a deep
green/black for the resistors, etc.

Anyone throw some light on the technology? I'll put a link to a pic if
needed.

Sounds a bit like thick film hybrid technology. Resistors were printed
with resistive ink and then if needed laser trimmed.

Right - I've heard of that. Is it still used? And wonder why they chose
that - there is any amount of space inside the instrument, so it could
easily have been a conventional PCB.

--
*It doesn't take a genius to spot a goat in a flock of sheep *

Dave Plowman London SW
To e-mail, change noise into sound.

Dave Plowman (News) wrote:
In article ,
Bob Minchin wrote:
Dave Plowman (News) wrote:
I've been looking at a Smith's revcounter from the '80s which has an
unusual (to me) PCB. The visible components are all standard - not
surface mount - but there are resistors and small caps which appear to
be part of the conductive layer. Not the usual surface mount stuff.

The actual board is some form of white plastic. There appear to be
three layers on the surface. Coloured light green, which covers most
of the board, a darker green which is the tracks and a deep
green/black for the resistors, etc.

Light green is the protective varnish, looking darker where the copper
and carbon show through.

Anyone throw some light on the technology? I'll put a link to a pic if
needed.

Sounds a bit like thick film hybrid technology. Resistors were printed
with resistive ink and then if needed laser trimmed.

Right - I've heard of that. Is it still used? And wonder why they chose
that - there is any amount of space inside the instrument, so it could
easily have been a conventional PCB.

More reliable in high vibration applications, due to the lack of
soldered joints, and cheaper to make, if you're making thousands of
identical units.

--
Tciao for Now!

John.

Dave Plowman (News) wrote:
I've been looking at a Smith's revcounter from the '80s which has an
unusual (to me) PCB. The visible components are all standard - not surface
mount - but there are resistors and small caps which appear to be part of
the conductive layer. Not the usual surface mount stuff.

The actual board is some form of white plastic. There appear to be three
layers on the surface. Coloured light green, which covers most of the
board, a darker green which is the tracks and a deep green/black for the
resistors, etc.

Anyone throw some light on the technology? I'll put a link to a pic if
needed.

Thin film

I might just know where a few brand new mechanisms of those exist if it
is needful.

In article ,
John Williamson wrote:
Right - I've heard of that. Is it still used? And wonder why they chose
that - there is any amount of space inside the instrument, so it could
easily have been a conventional PCB.

More reliable in high vibration applications, due to the lack of
soldered joints,

There are actually more soldered joints on this PCB than integrated
components. Vibration not really an issue.

and cheaper to make, if you're making thousands of
identical units.

Right. But all the other electronics in the car use 'conventional' PCBs -
including the Smiths OBC, which is a far more complicated device. But I
suppose the PCB in question could be used for all the various designs they
made.

--
*Why doesn't glue stick to the inside of the bottle?

Dave Plowman London SW
To e-mail, change noise into sound.

In article ,
The Natural Philosopher wrote:
Anyone throw some light on the technology? I'll put a link to a pic if
needed.

Thin film

I might just know where a few brand new mechanisms of those exist if it
is needful.

Can easily get a brand new one at low cost - it's on the SD1. But the one
I've stripped was for a 6 cylinder so no use for mine anyway - which still
works fine.

It's just one of these projects I so like. The original runs from the coil
negative. I'm looking at making new electronics so it works from much
lower level pulses. Like the tach output from an ECU driving COP etc.

--
*Can fat people go skinny-dipping?

Dave Plowman London SW
To e-mail, change noise into sound.

Dave Plowman (News) wrote:
In article ,
John Williamson wrote:
Right - I've heard of that. Is it still used? And wonder why they chose
that - there is any amount of space inside the instrument, so it could
easily have been a conventional PCB.

More reliable in high vibration applications, due to the lack of
soldered joints,

There are actually more soldered joints on this PCB than integrated
components. Vibration not really an issue.

and cheaper to make, if you're making thousands of
identical units.

Right. But all the other electronics in the car use 'conventional' PCBs -
including the Smiths OBC, which is a far more complicated device. But I
suppose the PCB in question could be used for all the various designs they
made.

they really only made one design!

IIRC it was a 10ma 270 degree meter..with a crappy pulse counter on it.

Dave Plowman (News) wrote:
In article ,
The Natural Philosopher wrote:
Anyone throw some light on the technology? I'll put a link to a pic if
needed.

Thin film

I might just know where a few brand new mechanisms of those exist if it
is needful.

Can easily get a brand new one at low cost - it's on the SD1. But the one
I've stripped was for a 6 cylinder so no use for mine anyway - which still
works fine.

It's just one of these projects I so like. The original runs from the coil
negative. I'm looking at making new electronics so it works from much
lower level pulses. Like the tach output from an ECU driving COP etc.

yeah. Mine became the 'analogue dial' in one of the firsts ever
digitally tuned radios..

we bought a few hundred...

In article ,
The Natural Philosopher wrote:
Right. But all the other electronics in the car use 'conventional'
PCBs - including the Smiths OBC, which is a far more complicated
device. But I suppose the PCB in question could be used for all the
various designs they made.

they really only made one design!

Not so - the first electronic Smiths tach (RV1? used two germanium
transistors. Mine has one IC. Which I suspect is just a 555 in drag.

IIRC it was a 10ma 270 degree meter..with a crappy pulse counter on it.

That was going to be another question - how to measure what the movement
is.

--
*Is there another word for synonym?

Dave Plowman London SW
To e-mail, change noise into sound.

On Wed, 03 Aug 2011 13:20:36 +0100, "Dave Plowman (News)"
wrote:

In article ,
The Natural Philosopher wrote:
Right. But all the other electronics in the car use 'conventional'
PCBs - including the Smiths OBC, which is a far more complicated
device. But I suppose the PCB in question could be used for all the
various designs they made.

they really only made one design!

Not so - the first electronic Smiths tach (RV1? used two germanium
transistors. Mine has one IC. Which I suspect is just a 555 in drag.

More than that, they also made the RVC which iirc was a single
transistor design.


--

On Aug 3, 9:20*am, "Dave Plowman (News)" wrote:
I've been looking at a Smith's revcounter from the '80s which has an
unusual (to me) PCB. The visible components are all standard - not surface
mount - but there are resistors and small caps which appear to be part of
the conductive layer. Not the usual surface mount stuff.

The actual board is some form of white plastic.

FR3


There appear to be three
layers on the surface. Coloured light green, which covers most of the
board, a darker green which is the tracks and a deep green/black for the
resistors, etc.

Anyone throw some light on the technology? I'll put a link to a pic if
needed.

Printed resistors are simple enough. Sounds like yours has gone one
step further with thick film circuitry to give embedded caps too.


NT

In article
,
NT wrote:
Printed resistors are simple enough. Sounds like yours has gone one
step further with thick film circuitry to give embedded caps too.

I'm not certain they are caps as I can't get any reading on my DVM.
Whereas I can on the resistors. There also appears to be some form of
transformer which feeds in the ignition pulses.

--
*Sticks and stones may break my bones but whips and chains excite me*

Dave Plowman London SW
To e-mail, change noise into sound.