On 23 Jan, 14:49, "Jimmie D" wrote:
"art" wrote in oglegroups.com...




snipurs did you have on this projector at failure? Part of
engineering a design is lifetime expectancy, judging by the projectors
I've seen over the past few years a three CRT projector has exceeded
it's expected lifetime.Doubt if it was a fault in engineering. If the engineers had their way it
would probably be a dale heatsinked to the chassis.Often one engineering
team designs it and another goes through to find out how they can cut
corners.- Hide quoted text -- Show quoted text -

Jimmy it is rare to use two resisters instead of one because a board
becomes bigger
and introduces cost. When you get to power resisters it is not unusual
to place two
in parallel and accept the cost. In this case a cost improver would
try to make the case
for one single resister instead of four since a Dale with heatsink
would be
comparitively prohibative. The engineers calculation for wattage may
well have
been correct without being side blinded by the fact of some square
form resisters.
Art

"art" wrote in message
oups.com...


On 23 Jan, 14:49, "Jimmie D" wrote:
"art" wrote in
oglegroups.com...




snipurs did you have on this projector at failure? Part of
engineering a design is lifetime expectancy, judging by the projectors
I've seen over the past few years a three CRT projector has exceeded
it's expected lifetime.Doubt if it was a fault in engineering. If the
engineers had their way it
would probably be a dale heatsinked to the chassis.Often one engineering
team designs it and another goes through to find out how they can cut
corners.- Hide quoted text -- Show quoted text -

Jimmy it is rare to use two resisters instead of one because a board
becomes bigger
and introduces cost. When you get to power resisters it is not unusual
to place two
in parallel and accept the cost. In this case a cost improver would
try to make the case
for one single resister instead of four since a Dale with heatsink
would be
comparitively prohibative. The engineers calculation for wattage may
well have
been correct without being side blinded by the fact of some square
form resisters.
Art


Depends on the cost of the resistors. Prices seem to increase somewhat
expotentially with wattage so the two smaller ones may have been cheaper
than one larger. In this case the cost improver would have went for the
multiple resistors.

art wrote:

On 23 Jan, 14:49, "Jimmie D" wrote:
"art" wrote in oglegroups.com...

...Part of
engineering a design is lifetime expectancy...
...Doubt if it was a fault in engineering. If the engineers had their way it
would probably be a dale heatsinked to the chassis.Often one engineering
team designs it and another goes through to find out how they can cut
corners.

Jimmy it is rare to use two resisters instead of one because a board
becomes bigger
and introduces cost.

If they used one resistor in another place or places it's could have
been easier to use multiples in series/parallel where they could rather
than purchase and stock another value at the factory. I worked at a
place where we used 5532 op amps in many audio circuits and in one place
as a flip flop so we wouldn't have to stock a 74xx or 40xx just for that
one use. It was easier on the assemblers to have one bin of chips,
better quantity pricing, no sweating running out of one part kept in
smaller quantity, (insert more bean counter stuff...)

On 23 Jan, 18:14, gwatts wrote:
art wrote:

On 23 Jan, 14:49, "Jimmie D" wrote:
"art" wrote in oglegroups.com...

...Part of
snip where we used 5532 op amps in many audio circuits and in one place
as a flip flop so we wouldn't have to stock a 74xx or 40xx just for that
one use. It was easier on the assemblers to have one bin of chips,
better quantity pricing, no sweating running out of one part kept in
smaller quantity, (insert more bean counter stuff...)

Very interesting if you are refering to power resisters used in a
non switching power supply. In my case I have had no experience
of seeing power supplies with excess resisters or with the use of dale
prescision resisters or resisters mounted on a heat sink which
is fortunate for me otherwise I would never have resolved my
particular problem It would appear that I retired just in time
before engineering studies became out of fashion
Happy trails
Art

art wrote:

On 23 Jan, 18:14, gwatts wrote:

art wrote:


On 23 Jan, 14:49, "Jimmie D" wrote:

"art" wrote in oglegroups.com...

...Part of

snip where we used 5532 op amps in many audio circuits and in one place

as a flip flop so we wouldn't have to stock a 74xx or 40xx just for that
one use. It was easier on the assemblers to have one bin of chips,
better quantity pricing, no sweating running out of one part kept in
smaller quantity, (insert more bean counter stuff...)


Very interesting if you are refering to power resisters used in a
non switching power supply.

Your particular case sounds like they designed for one resistor and
designed very close to the function/failure edge, then rushed to
production only to discover the single resistor was too far over that
edge. Their solution was to quickly change the board design for four in
series-parallel but put them in the same space, since they already had
umpteen thousand resistors ordered or even in stock. It worked in test,
worked for a week or so running continuously... ship it!

... It would appear that I retired just in time
before engineering studies became out of fashion

Engineering studies aren't out of fashion, in fact they're more
intensive, involve a lot more computer modeling and help push the design
closer to the function/failure edge. Not out of fashion but a smaller
piece of the pie, now the design involves a lot more
design-for-manufacture including pick-and-place instead of a human
assembler, all SMT (see previous reason), least component count
possible, limited lifetime so you have to buy a new unit in a few years,
less 'robust design' and more 'economical,' higher profit and lower quality.

Don't blame the engineers, unless they went on to get an MBA after the
EE, ME, etc. I got out of private industry ten years ago for these
reasons, I was tired of design reviews where management pushed the 'you
can cut this out, it won't be so bad' line. Designs aren't for the
benefit of the customer, they are for the benefit of the stockholder and
the board of directors. What was 'The quality goes in before the name
goes on,' is now 'the profit is determined before the unit is produced.'
I'm not saying that profit isn't a good thing, just that it shouldn't
be the overwhelming thing.

73,
W8LNA

On Wed, 24 Jan 2007 12:40:32 GMT, gwatts
wrote:

I was tired of design reviews where management pushed the 'you
can cut this out, it won't be so bad' line.

Hi OM,

My very first EE professor (also an engineer at the HP division in
Colorado Springs) taught us the merits of designs meeting the
expectations of Mad Man Muntz.

Muntz was a car salesman who entered the nascent field of TV in the
late 40s and would wander the design lab with a pair of dikes in his
pocket. Looking over the shoulder of any designer he would snip out
components until they lost the picture, it would roll, or the sound
would go dead. Then he would suggest they put back in the last
snipped component.

He discovered his TVs didn't need synchronization circuits because his
market was in urban cities where the signal was so powerful as to
provide enough level to be self-syncing. I know, because I fixed many
of those TVs that eventually found their way into the Burbs, and were
forever rolling unless you found the sweet spot on the horizontal or
vertical adjustment (always in the back).

73's
Richard Clark, KB7QHC

Richard Clark wrote:
On Wed, 24 Jan 2007 12:40:32 GMT, gwatts
wrote:


I was tired of design reviews where management pushed the 'you
can cut this out, it won't be so bad' line.


Hi OM,

My very first EE professor (also an engineer at the HP division in
Colorado Springs) taught us the merits of designs meeting the
expectations of Mad Man Muntz...he would snip out
components until they lost the picture, it would roll, or the sound
would go dead. Then he would suggest they put back in the last
snipped component.

He discovered his TVs didn't need synchronization circuits because his
market was in urban cities where the signal was so powerful as to
provide enough level to be self-syncing. I know, because I fixed many
of those TVs that eventually found their way into the Burbs, and were
forever rolling unless you found the sweet spot on the horizontal or
vertical adjustment (always in the back).

Yes, I've heard the tales of M. M. Muntz, but apparently so had the head
designer at the audio mfr I worked at. They had a VCA circuit using a
well known VCA chip. The data sheet notes mentioned a small value
capacitor across two pins for stability. The designer discovered his
circuit would work just as well without the cap and thus left it out of
his design, so far out that there weren't even traces or pads to put the
cap in should it become necessary (you can see where this is going,
no?). The VCA vendor outsourced fabrication of the chip and all of a
sudden the noise level of the VCA circuit would jump about 70 dB as the
fader reached the bottom of travel, not desirable in an audio
application. I spent a little time perusing the data sheets and our
schematics, noticed the cap omission, soldered a cap across the pins of
an offending circuit and within the hour we had the assemblers tack
soldering caps we bought at a local electronics shop (not RS) onto
assembled modules. The designer's comment was 'Well, it worked for
quite a while...' Later we found customers with similar noise level
jumps using pre-outsourced VCAs. Yes, they saved a few pennies on each
module but lost about two dozen customers when they figured out what had
been left out of their very expensive audio equipment.

When I started at that place I was told not to make suggestions
regarding modifications of existing designs lest I offend the managing
'engineer'.

gwatts wrote:
Richard Clark wrote:
On Wed, 24 Jan 2007 12:40:32 GMT, gwatts
wrote:


I was tired of design reviews where management pushed the 'you can
cut this out, it won't be so bad' line.


Hi OM,

My very first EE professor (also an engineer at the HP division in
Colorado Springs) taught us the merits of designs meeting the
expectations of Mad Man Muntz...he would snip out
components until they lost the picture, it would roll, or the sound
would go dead. Then he would suggest they put back in the last
snipped component.

He discovered his TVs didn't need synchronization circuits because his
market was in urban cities where the signal was so powerful as to
provide enough level to be self-syncing. I know, because I fixed many
of those TVs that eventually found their way into the Burbs, and were
forever rolling unless you found the sweet spot on the horizontal or
vertical adjustment (always in the back).

Yes, I've heard the tales of M. M. Muntz, but apparently so had the head
designer at the audio mfr I worked at. They had a VCA circuit using a
well known VCA chip. The data sheet notes mentioned a small value
capacitor across two pins for stability. The designer discovered his
circuit would work just as well without the cap and thus left it out of
his design, so far out that there weren't even traces or pads to put the
cap in should it become necessary (you can see where this is going,
no?). The VCA vendor outsourced fabrication of the chip and all of a
sudden the noise level of the VCA circuit would jump about 70 dB as the
fader reached the bottom of travel, not desirable in an audio
application. I spent a little time perusing the data sheets and our
schematics, noticed the cap omission, soldered a cap across the pins of
an offending circuit and within the hour we had the assemblers tack
soldering caps we bought at a local electronics shop (not RS) onto
assembled modules. The designer's comment was 'Well, it worked for
quite a while...' Later we found customers with similar noise level
jumps using pre-outsourced VCAs. Yes, they saved a few pennies on each
module but lost about two dozen customers when they figured out what had
been left out of their very expensive audio equipment.

When I started at that place I was told not to make suggestions
regarding modifications of existing designs lest I offend the managing
'engineer'.


This reminds me of an old story about how you can become a hero in
Detroit. Save 1/2 cent each on 10 million washers. To become a bum in
Detroit, have those washers cause a 10 million car recall.

Dave N

On Wed, 24 Jan 2007 18:20:51 GMT, gwatts
wrote:

When I started at that place I was told not to make suggestions
regarding modifications of existing designs lest I offend the managing
'engineer'.

I feel your pain.

I followed one bum who couldn't figure out the gozinta from the
comesoutta on a linear IC. The design (heart monitor) went all the
way through to production, then testing, and they wondered why the
processor only produced a flat line for any patient. I also came to
the conclusion that the project engineer was brain dead too (design
review an exercise in swinging rubber stamps). I have forever after
examined the equipment of any hospital I had procedures in. There was
one trademark I didn't want to see.

Consulting can be a tough life of techno-whoring. Praise the idiots
(or repress the urge to strangle) and clean up their mess.

73's
Richard Clark, KB7QHC

"Richard Clark" wrote in message
...
On Wed, 24 Jan 2007 12:40:32 GMT, gwatts
wrote:

I was tired of design reviews where management pushed the 'you
can cut this out, it won't be so bad' line.

Hi OM,

My very first EE professor (also an engineer at the HP division in
Colorado Springs) taught us the merits of designs meeting the
expectations of Mad Man Muntz.

Muntz was a car salesman who entered the nascent field of TV in the
late 40s and would wander the design lab with a pair of dikes in his
pocket. Looking over the shoulder of any designer he would snip out
components until they lost the picture, it would roll, or the sound
would go dead. Then he would suggest they put back in the last
snipped component.

He discovered his TVs didn't need synchronization circuits because his
market was in urban cities where the signal was so powerful as to
provide enough level to be self-syncing. I know, because I fixed many
of those TVs that eventually found their way into the Burbs, and were
forever rolling unless you found the sweet spot on the horizontal or
vertical adjustment (always in the back).

73's
Richard Clark, KB7QHC

Oh, you reveal you age. I worked on a bunch of those until I just started
not letting them in the door. Seems a guy bought a bunch(100+) from a
motel(s) that had gotten new TVs and had sold the for about $30 a piece. I
think they had a 1 tube IF if I remember right. They wouldnt work at all in
our area unles you had a really good antenna on a tall tower. The only
places that had this was the shop I worked in and the local motels.

Jimmie