Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems.

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
  #11   Report Post  
Old December 31st 15, 05:14 PM posted to sci.electronics.repair
external usenet poster
 
First recorded activity by DIYBanter: Jul 2007
Posts: 3,907
Default Diffferent techniques in troubleshooting

On Wed, 30 Dec 2015 16:10:40 -0800 (PST), John Heath
wrote:

I would like to know if others have found this to be true.


It's true, but only if you have a production line environment. During
the late 1960's, I worked for a company that did warranty service on
mostly consumer tape recorders. We would get the rejects and returns
from the distributor. We had 4 people working the line. One to unbox
and machine and organize the paperwork. One do to nothing but
diagnostics. Me to tear it apart and do parts replacement, more
testing, and reassembly. One more to do more paperwork, a final
check, and reboxing. Anything that couldn't be fixed in 10-15 mins
was put aside for later troubleshooting. Anything with more than 5
faults was deemed not worth repairing. It was quite efficient. As I
vaguely recall, we could do about 4 to 10 machines per hour.

What was interesting was the general lack of test equipment. As you
noted, it takes far too much time to setup and probe. For audio,
putting a finger on the base of a transistor and listening for hum
worked well. To make it quick an easy, we had cardboard templates,
with holes punched for all the common injection points with notes on
what to expect.

Head alignment and channel balancing was a different story. For that,
we had a separate test fixture near final check. It had an audio
generator and oscilloscope, but with a good ear, the scope wasn't
really necessary. Unfortunately, this doubled the cycle time adding
an additional 4 to 10 minutes.

After you've worked on several hundred of exactly the same model tape
recorder, you see patterns of failure. For example, if some component
was inserted backwards on the first 10 or so units, it's a fair guess
that the rest had the same problem. So, pre-emptive replacement was
possible and worked well.

Fast forward 30 years and I'm now doing marine radios and data
transceivers. Over about a 10 year period, I was either involved or
watched at least 5 different product test and QA systems. The one
that worked best was visual inspection. I brought some of the
assemblers into test to do the inspection. They couldn't read a
resistor color code, but they could spot anything that had changed
quite easily. The worst was a complex series of bench tests required
by the customer, which involved a large pile of test equipment. I did
a quick time-and-motion study and found that 30% of the test time was
in setup, changing setup, and teardown. This would have been a great
candidate for computer driven ATE (automagic test equipment) except
that the PC of fashion at the time was an Apple III and RS Model II.
We tried, and failed. So, we continued to use a pile of test
equipment for test and troubleshooting. After about 3 years of this,
some of the rotary switches on the HP equipment started to fail.

Somewhat later, I had changed company and now had a product with
sufficient quantity to justify ATE. The PC of fashion was the HP 9816
with an HP-IB(IEEE488) bus. It controlled a rack full of HP RF test
equipment. I don't have time to go into detail on the setup. When it
worked, it was great and could test, align(tune), print measurements,
print reports, and live test amazingly quickly. When it didn't work,
everything came to a grinding halt. I recall having 4 techs at idle
while someone furiously drove to Fry's to buy a replacement part. I
wanted to build a manually operated backup test line but management
vetoed the idea. Getting all the equipment calibrated at the same
time was tricky, but reduced downtime. ATE would have been a marginal
failure had I not been able to "borrow" test equipment from the
engineering dept.

However, that was production test, not troubleshooting. When the
manual or ATE test line declared something worthy of troubleshooting,
it was NOT done while there were units waiting to be tested. If the
products were cheap enough, they could just be "remanufactured" which
means tear them apart down to the board level, run them back through
board test, and build a "new" unit. This worked well with radios that
had plugin cards. Eventually, there was a backlog of boards to be
troubleshot. Usually between production runs and contracts, someone
would decide that it's time to clean up the backlog. However, instead
of having the test techs do the troubleshooting, the engineer who
designed the radio would be sentence to overtime diagnosing the
boards. Yeah, that was usually me. Unless the problem was trivial, I
would only tag the likely parts, borrow someone that could do the
soldering, retest the board, and send it on to production test. This
worked well when we needed 25 identical board immediately, and was a
total waste of time for 5 or less boards that took too long to setup.

Today, much of what I see is ATE run by techs that only know how to
push the buttons. Troubleshooting is done partly with BITE (built in
test equipment). Parts replacement and soldering is outsourced to a
contractor, specialty shop, or refurbisher. In short, there's nobody
on the production line that knows which end of the soldering iron to
grab, much less how the product actually works. The rule is that
production must continue unimpeded by any form of troubleshooting or
repair. If there is any troubleshooting, it's to fix the production
line and ATE, not the actual product.

Might as well say something about bugs and fixes. With todays fairly
short product lives (typically about 6 months), it's not uncommon for
a company to have 3 or 4 generations of replacement products in
development at the same time. If something is found lacking or
defective in the current product, it is cheaper and easier to simply
wait for the next model to appear in production, and replace it with a
later version. What this means is that NOTHING gets fixed in
production, even when it's a known problem, easy fix, or major
enhancement. If you see products with known design flaws that
continue to be manufactured with the flaws, you now know why.
http://www.designnews.com/archives.asp?section_id=1367

Of course, there will still be independent repair shops (like mine)
that fix things one at a time. They're a dying breed mostly because
of the declining cost of modern electronics. As the retail price of
new hardware declines, the amount of money that a customer is willing
to pay for a repair also declines. As a rule-of-thumb, most customers
will buy a new replacment instead of repairing something when the
repair cost exceeds 50% of the replacement cost. So, if someone drags
in an out of warranty laptop that cost them $500 about 3 years ago, my
maximum bill (parts+labor) cannot exceed $250. Assuming no parts were
replaced, that 3.3 hrs at $75/hr. The number of things I can fix in
under 3.3 hrs is rapidly shrinking. For example, I have an APC XS1300
UPS on the bench that can be purchased new for about $125. In order
to replace one lousy bulging electrolytic capacitor, I've already
burned 2 hrs and I'm not done. Can I bill the customer $150 to fix a
$125 UPS? Nope.

So, the question isn't as much how to troubleshoot, but whether it's
worth you time troubleshooting in the first place.

Happy end of the tax year.



--
Jeff Liebermann
150 Felker St #D
http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

  #12   Report Post  
Old December 31st 15, 06:46 PM posted to sci.electronics.repair
external usenet poster
 
First recorded activity by DIYBanter: Aug 2006
Posts: 1,748
Default Diffferent techniques in troubleshooting

Per Jeff Liebermann:
What was interesting was the general lack of test equipment. As you
noted, it takes far too much time to setup and probe. For audio,
putting a finger on the base of a transistor and listening for hum
worked well. To make it quick an easy, we had cardboard templates,
with holes punched for all the common injection points with notes on
what to expect.


I "repaired" early digital-type equipment in the Air Force.

Quotes because it turned out that all we did was find the failed circuit
boards and replace them - leaving the actual repair work on the boards
to the old-timers.

We were told "Follow your nose".... and that proved to be the way almost
all of the time.... you could locate the board with the failed component
by smell and then visually verify after the board was pulled.

I don't suppose that monkeys could be trained to do that.... but I am
pretty sure than anybody with a room-temperature IQ could....

Six months of technical training at taxpayer expense down the drain....
Oh well.... -)
--
Pete Cresswell
  #13   Report Post  
Old December 31st 15, 08:14 PM posted to sci.electronics.repair
external usenet poster
 
First recorded activity by DIYBanter: Dec 2015
Posts: 41
Default Diffferent techniques in troubleshooting

On Thursday, December 31, 2015 at 12:14:59 PM UTC-5, Jeff Liebermann wrote:
On Wed, 30 Dec 2015 16:10:40 -0800 (PST), John Heath
wrote:

I would like to know if others have found this to be true.


It's true, but only if you have a production line environment. During
the late 1960's, I worked for a company that did warranty service on
mostly consumer tape recorders. We would get the rejects and returns
from the distributor. We had 4 people working the line. One to unbox
and machine and organize the paperwork. One do to nothing but
diagnostics. Me to tear it apart and do parts replacement, more
testing, and reassembly. One more to do more paperwork, a final
check, and reboxing. Anything that couldn't be fixed in 10-15 mins
was put aside for later troubleshooting. Anything with more than 5
faults was deemed not worth repairing. It was quite efficient. As I
vaguely recall, we could do about 4 to 10 machines per hour.

What was interesting was the general lack of test equipment. As you
noted, it takes far too much time to setup and probe. For audio,
putting a finger on the base of a transistor and listening for hum
worked well. To make it quick an easy, we had cardboard templates,
with holes punched for all the common injection points with notes on
what to expect.

Head alignment and channel balancing was a different story. For that,
we had a separate test fixture near final check. It had an audio
generator and oscilloscope, but with a good ear, the scope wasn't
really necessary. Unfortunately, this doubled the cycle time adding
an additional 4 to 10 minutes.

After you've worked on several hundred of exactly the same model tape
recorder, you see patterns of failure. For example, if some component
was inserted backwards on the first 10 or so units, it's a fair guess
that the rest had the same problem. So, pre-emptive replacement was
possible and worked well.

Fast forward 30 years and I'm now doing marine radios and data
transceivers. Over about a 10 year period, I was either involved or
watched at least 5 different product test and QA systems. The one
that worked best was visual inspection. I brought some of the
assemblers into test to do the inspection. They couldn't read a
resistor color code, but they could spot anything that had changed
quite easily. The worst was a complex series of bench tests required
by the customer, which involved a large pile of test equipment. I did
a quick time-and-motion study and found that 30% of the test time was
in setup, changing setup, and teardown. This would have been a great
candidate for computer driven ATE (automagic test equipment) except
that the PC of fashion at the time was an Apple III and RS Model II.
We tried, and failed. So, we continued to use a pile of test
equipment for test and troubleshooting. After about 3 years of this,
some of the rotary switches on the HP equipment started to fail.

Somewhat later, I had changed company and now had a product with
sufficient quantity to justify ATE. The PC of fashion was the HP 9816
with an HP-IB(IEEE488) bus. It controlled a rack full of HP RF test
equipment. I don't have time to go into detail on the setup. When it
worked, it was great and could test, align(tune), print measurements,
print reports, and live test amazingly quickly. When it didn't work,
everything came to a grinding halt. I recall having 4 techs at idle
while someone furiously drove to Fry's to buy a replacement part. I
wanted to build a manually operated backup test line but management
vetoed the idea. Getting all the equipment calibrated at the same
time was tricky, but reduced downtime. ATE would have been a marginal
failure had I not been able to "borrow" test equipment from the
engineering dept.

However, that was production test, not troubleshooting. When the
manual or ATE test line declared something worthy of troubleshooting,
it was NOT done while there were units waiting to be tested. If the
products were cheap enough, they could just be "remanufactured" which
means tear them apart down to the board level, run them back through
board test, and build a "new" unit. This worked well with radios that
had plugin cards. Eventually, there was a backlog of boards to be
troubleshot. Usually between production runs and contracts, someone
would decide that it's time to clean up the backlog. However, instead
of having the test techs do the troubleshooting, the engineer who
designed the radio would be sentence to overtime diagnosing the
boards. Yeah, that was usually me. Unless the problem was trivial, I
would only tag the likely parts, borrow someone that could do the
soldering, retest the board, and send it on to production test. This
worked well when we needed 25 identical board immediately, and was a
total waste of time for 5 or less boards that took too long to setup.

Today, much of what I see is ATE run by techs that only know how to
push the buttons. Troubleshooting is done partly with BITE (built in
test equipment). Parts replacement and soldering is outsourced to a
contractor, specialty shop, or refurbisher. In short, there's nobody
on the production line that knows which end of the soldering iron to
grab, much less how the product actually works. The rule is that
production must continue unimpeded by any form of troubleshooting or
repair. If there is any troubleshooting, it's to fix the production
line and ATE, not the actual product.

Might as well say something about bugs and fixes. With todays fairly
short product lives (typically about 6 months), it's not uncommon for
a company to have 3 or 4 generations of replacement products in
development at the same time. If something is found lacking or
defective in the current product, it is cheaper and easier to simply
wait for the next model to appear in production, and replace it with a
later version. What this means is that NOTHING gets fixed in
production, even when it's a known problem, easy fix, or major
enhancement. If you see products with known design flaws that
continue to be manufactured with the flaws, you now know why.
http://www.designnews.com/archives.asp?section_id=1367

Of course, there will still be independent repair shops (like mine)
that fix things one at a time. They're a dying breed mostly because
of the declining cost of modern electronics. As the retail price of
new hardware declines, the amount of money that a customer is willing
to pay for a repair also declines. As a rule-of-thumb, most customers
will buy a new replacment instead of repairing something when the
repair cost exceeds 50% of the replacement cost. So, if someone drags
in an out of warranty laptop that cost them $500 about 3 years ago, my
maximum bill (parts+labor) cannot exceed $250. Assuming no parts were
replaced, that 3.3 hrs at $75/hr. The number of things I can fix in
under 3.3 hrs is rapidly shrinking. For example, I have an APC XS1300
UPS on the bench that can be purchased new for about $125. In order
to replace one lousy bulging electrolytic capacitor, I've already
burned 2 hrs and I'm not done. Can I bill the customer $150 to fix a
$125 UPS? Nope.

So, the question isn't as much how to troubleshoot, but whether it's
worth you time troubleshooting in the first place.

Happy end of the tax year.



--
Jeff Liebermann
150 Felker St #D
http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558


Sounds like you touched a lot of bases in the service life. I took a similar path ending up self employed for about the last 25 years. It has changed so much from the old days walking around with a tube caddy cleaning TV tuners. I now walk around with a laptop pinging IP addresses. How did that happen? I think the writing is on the wall. How many shoe repair and watch repair shops do you see. The electronic repair tech could meet the same fate. Just the other day I saw a flat screen monitor sitting in a garbage bin. To see the rain falling on it was too much so I took it inside. When I plugged it in everything worked and it had a VGA plus DVI input! What was that doing in the garbage. My only guess is someone wanted a wider flatter monitor so he or she tossed it out. I am typing on that monitor as we speak. How can one make a living in service with this going on. It is so bad that I have to work on 50,000 dollar LED displays boards. They will still fix those at that price. Just about everything else is disposable. However I have no regrets as electronics has been an existing ride with technology changing so fast that there is never a dull moment.
  #14   Report Post  
Old December 31st 15, 08:28 PM posted to sci.electronics.repair
external usenet poster
 
First recorded activity by DIYBanter: Jul 2006
Posts: 769
Default Diffferent techniques in troubleshooting

On 12/31/2015 12:14 PM, John Heath wrote:
On Thursday, December 31, 2015 at 12:14:59 PM UTC-5, Jeff Liebermann wrote:
On Wed, 30 Dec 2015 16:10:40 -0800 (PST), John Heath
wrote:

I would like to know if others have found this to be true.


It's true, but only if you have a production line environment. During
the late 1960's, I worked for a company that did warranty service on
mostly consumer tape recorders. We would get the rejects and returns
from the distributor. We had 4 people working the line. One to unbox
and machine and organize the paperwork. One do to nothing but
diagnostics. Me to tear it apart and do parts replacement, more
testing, and reassembly. One more to do more paperwork, a final
check, and reboxing. Anything that couldn't be fixed in 10-15 mins
was put aside for later troubleshooting. Anything with more than 5
faults was deemed not worth repairing. It was quite efficient. As I
vaguely recall, we could do about 4 to 10 machines per hour.

What was interesting was the general lack of test equipment. As you
noted, it takes far too much time to setup and probe. For audio,
putting a finger on the base of a transistor and listening for hum
worked well. To make it quick an easy, we had cardboard templates,
with holes punched for all the common injection points with notes on
what to expect.

Head alignment and channel balancing was a different story. For that,
we had a separate test fixture near final check. It had an audio
generator and oscilloscope, but with a good ear, the scope wasn't
really necessary. Unfortunately, this doubled the cycle time adding
an additional 4 to 10 minutes.

After you've worked on several hundred of exactly the same model tape
recorder, you see patterns of failure. For example, if some component
was inserted backwards on the first 10 or so units, it's a fair guess
that the rest had the same problem. So, pre-emptive replacement was
possible and worked well.

Fast forward 30 years and I'm now doing marine radios and data
transceivers. Over about a 10 year period, I was either involved or
watched at least 5 different product test and QA systems. The one
that worked best was visual inspection. I brought some of the
assemblers into test to do the inspection. They couldn't read a
resistor color code, but they could spot anything that had changed
quite easily. The worst was a complex series of bench tests required
by the customer, which involved a large pile of test equipment. I did
a quick time-and-motion study and found that 30% of the test time was
in setup, changing setup, and teardown. This would have been a great
candidate for computer driven ATE (automagic test equipment) except
that the PC of fashion at the time was an Apple III and RS Model II.
We tried, and failed. So, we continued to use a pile of test
equipment for test and troubleshooting. After about 3 years of this,
some of the rotary switches on the HP equipment started to fail.

Somewhat later, I had changed company and now had a product with
sufficient quantity to justify ATE. The PC of fashion was the HP 9816
with an HP-IB(IEEE488) bus. It controlled a rack full of HP RF test
equipment. I don't have time to go into detail on the setup. When it
worked, it was great and could test, align(tune), print measurements,
print reports, and live test amazingly quickly. When it didn't work,
everything came to a grinding halt. I recall having 4 techs at idle
while someone furiously drove to Fry's to buy a replacement part. I
wanted to build a manually operated backup test line but management
vetoed the idea. Getting all the equipment calibrated at the same
time was tricky, but reduced downtime. ATE would have been a marginal
failure had I not been able to "borrow" test equipment from the
engineering dept.

However, that was production test, not troubleshooting. When the
manual or ATE test line declared something worthy of troubleshooting,
it was NOT done while there were units waiting to be tested. If the
products were cheap enough, they could just be "remanufactured" which
means tear them apart down to the board level, run them back through
board test, and build a "new" unit. This worked well with radios that
had plugin cards. Eventually, there was a backlog of boards to be
troubleshot. Usually between production runs and contracts, someone
would decide that it's time to clean up the backlog. However, instead
of having the test techs do the troubleshooting, the engineer who
designed the radio would be sentence to overtime diagnosing the
boards. Yeah, that was usually me. Unless the problem was trivial, I
would only tag the likely parts, borrow someone that could do the
soldering, retest the board, and send it on to production test. This
worked well when we needed 25 identical board immediately, and was a
total waste of time for 5 or less boards that took too long to setup.

Today, much of what I see is ATE run by techs that only know how to
push the buttons. Troubleshooting is done partly with BITE (built in
test equipment). Parts replacement and soldering is outsourced to a
contractor, specialty shop, or refurbisher. In short, there's nobody
on the production line that knows which end of the soldering iron to
grab, much less how the product actually works. The rule is that
production must continue unimpeded by any form of troubleshooting or
repair. If there is any troubleshooting, it's to fix the production
line and ATE, not the actual product.

Might as well say something about bugs and fixes. With todays fairly
short product lives (typically about 6 months), it's not uncommon for
a company to have 3 or 4 generations of replacement products in
development at the same time. If something is found lacking or
defective in the current product, it is cheaper and easier to simply
wait for the next model to appear in production, and replace it with a
later version. What this means is that NOTHING gets fixed in
production, even when it's a known problem, easy fix, or major
enhancement. If you see products with known design flaws that
continue to be manufactured with the flaws, you now know why.
http://www.designnews.com/archives.asp?section_id=1367

Of course, there will still be independent repair shops (like mine)
that fix things one at a time. They're a dying breed mostly because
of the declining cost of modern electronics. As the retail price of
new hardware declines, the amount of money that a customer is willing
to pay for a repair also declines. As a rule-of-thumb, most customers
will buy a new replacment instead of repairing something when the
repair cost exceeds 50% of the replacement cost. So, if someone drags
in an out of warranty laptop that cost them $500 about 3 years ago, my
maximum bill (parts+labor) cannot exceed $250. Assuming no parts were
replaced, that 3.3 hrs at $75/hr. The number of things I can fix in
under 3.3 hrs is rapidly shrinking. For example, I have an APC XS1300
UPS on the bench that can be purchased new for about $125. In order
to replace one lousy bulging electrolytic capacitor, I've already
burned 2 hrs and I'm not done. Can I bill the customer $150 to fix a
$125 UPS? Nope.

So, the question isn't as much how to troubleshoot, but whether it's
worth you time troubleshooting in the first place.

Happy end of the tax year.



--
Jeff Liebermann
150 Felker St #D
http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558


Sounds like you touched a lot of bases in the service life. I took a similar path ending up self employed for about the last 25 years. It has changed so much from the old days walking around with a tube caddy cleaning TV tuners. I now walk around with a laptop pinging IP addresses. How did that happen? I think the writing is on the wall. How many shoe repair and watch repair shops do you see. The electronic repair tech could meet the same fate. Just the other day I saw a flat screen monitor sitting in a garbage bin. To see the rain falling on it was too much so I took it inside. When I plugged it in everything worked and it had a VGA plus DVI input! What was that doing in the garbage. My only guess is someone wanted a wider flatter monitor so he or she tossed it out. I am typing on that monitor as we speak. How can one make a living in service with this going on. It is so bad that I have to work on 50,000 dollar LED displays boards. They will still fix those at that price. Just abou

t everything else is disposable. However I have no regrets as electronics has been an existing ride with technology changing so fast that there is never a dull moment.


There is always arcade game repair. There is enough interest in that
that most cities need a few people who do house calls.

John :-#)#

--
(Please post followups or tech inquiries to the USENET newsgroup)
John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9
(604)872-5757 or Fax 872-2010 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."
  #15   Report Post  
Old January 1st 16, 12:59 AM posted to sci.electronics.repair
external usenet poster
 
First recorded activity by DIYBanter: Jul 2007
Posts: 3,907
Default Diffferent techniques in troubleshooting

On Thu, 31 Dec 2015 13:46:01 -0500, "(PeteCresswell)"
wrote:

I "repaired" early digital-type equipment in the Air Force.

Quotes because it turned out that all we did was find the failed circuit
boards and replace them - leaving the actual repair work on the boards
to the old-timers.


In my checkered past, I once helped design two direction finders for
the USCG AN/SRD-21 and 22. After shipping a fair number of these
radios, I was given a tour of the local repair facility on Treasure
Island in SF Bay. Sitting pilled in one corner was about 50 radios,
in various stages of cannibalization. So much for spare parts.

We were told "Follow your nose".... and that proved to be the way almost
all of the time.... you could locate the board with the failed component
by smell and then visually verify after the board was pulled.


Yeah, I do the same. I would prefer an FLIR infrared imager, but the
nose will do for now. I also have a NIKKEN #1394 "air wellness air
quality monitor".
http://802.11junk.com/jeffl/crud/Nikken-AQM.jpg
It's a nephelmometer which uses light scattering to detect airborne
dust particles.
http://en.wikipedia.org/wiki/Nephelometer
Overkill:
http://www.esrl.noaa.gov/gmd/aero/instrumentation/neph_desc.html
It's been useful for finding what is burning in the office and
locating the component producing the smoke. I've also used it to
chase down the source of a white dust in a customers air ducts.

--
Jeff Liebermann
150 Felker St #D
http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558


  #16   Report Post  
Old January 1st 16, 08:05 AM posted to sci.electronics.repair
external usenet poster
 
First recorded activity by DIYBanter: Aug 2014
Posts: 1,024
Default Diffferent techniques in troubleshooting

John Robertson wrote:


Google "blue meter" or "Bob Parkers ESR meter".


Indeed, I've been selling those meters since 1999 when I first starting
chatting with Bob Parker (Dick Smith K-7204 kits in those days). Great
ESR meter that works in circuit for roughly values between 4ufd to about
1000ufd.


** I find Bob's ESR meter useful with electro caps anywhere from 1uF to over 15,000uF. It also checks the ESR of tantalum electros. film caps from about 0.47uF upwards - for shorts and opens.

Another use is with batteries, particularly Lithium button cells plus any type of AA, AA and 9V battery.

As with caps, known good examples are your reference and ESR readings rise as the cell goes flat. A 20x3mm Lithium reads about 10 ohms when new rising to 100 ohms or more at end of life.


.... Phil







  #17   Report Post  
Old January 1st 16, 08:23 AM posted to sci.electronics.repair
external usenet poster
 
First recorded activity by DIYBanter: Dec 2015
Posts: 41
Default Diffferent techniques in troubleshooting

On Thursday, December 31, 2015 at 3:28:53 PM UTC-5, John Robertson wrote:
On 12/31/2015 12:14 PM, John Heath wrote:
On Thursday, December 31, 2015 at 12:14:59 PM UTC-5, Jeff Liebermann wrote:
On Wed, 30 Dec 2015 16:10:40 -0800 (PST), John Heath
wrote:

I would like to know if others have found this to be true.

It's true, but only if you have a production line environment. During
the late 1960's, I worked for a company that did warranty service on
mostly consumer tape recorders. We would get the rejects and returns
from the distributor. We had 4 people working the line. One to unbox
and machine and organize the paperwork. One do to nothing but
diagnostics. Me to tear it apart and do parts replacement, more
testing, and reassembly. One more to do more paperwork, a final
check, and reboxing. Anything that couldn't be fixed in 10-15 mins
was put aside for later troubleshooting. Anything with more than 5
faults was deemed not worth repairing. It was quite efficient. As I
vaguely recall, we could do about 4 to 10 machines per hour.

What was interesting was the general lack of test equipment. As you
noted, it takes far too much time to setup and probe. For audio,
putting a finger on the base of a transistor and listening for hum
worked well. To make it quick an easy, we had cardboard templates,
with holes punched for all the common injection points with notes on
what to expect.

Head alignment and channel balancing was a different story. For that,
we had a separate test fixture near final check. It had an audio
generator and oscilloscope, but with a good ear, the scope wasn't
really necessary. Unfortunately, this doubled the cycle time adding
an additional 4 to 10 minutes.

After you've worked on several hundred of exactly the same model tape
recorder, you see patterns of failure. For example, if some component
was inserted backwards on the first 10 or so units, it's a fair guess
that the rest had the same problem. So, pre-emptive replacement was
possible and worked well.

Fast forward 30 years and I'm now doing marine radios and data
transceivers. Over about a 10 year period, I was either involved or
watched at least 5 different product test and QA systems. The one
that worked best was visual inspection. I brought some of the
assemblers into test to do the inspection. They couldn't read a
resistor color code, but they could spot anything that had changed
quite easily. The worst was a complex series of bench tests required
by the customer, which involved a large pile of test equipment. I did
a quick time-and-motion study and found that 30% of the test time was
in setup, changing setup, and teardown. This would have been a great
candidate for computer driven ATE (automagic test equipment) except
that the PC of fashion at the time was an Apple III and RS Model II.
We tried, and failed. So, we continued to use a pile of test
equipment for test and troubleshooting. After about 3 years of this,
some of the rotary switches on the HP equipment started to fail.

Somewhat later, I had changed company and now had a product with
sufficient quantity to justify ATE. The PC of fashion was the HP 9816
with an HP-IB(IEEE488) bus. It controlled a rack full of HP RF test
equipment. I don't have time to go into detail on the setup. When it
worked, it was great and could test, align(tune), print measurements,
print reports, and live test amazingly quickly. When it didn't work,
everything came to a grinding halt. I recall having 4 techs at idle
while someone furiously drove to Fry's to buy a replacement part. I
wanted to build a manually operated backup test line but management
vetoed the idea. Getting all the equipment calibrated at the same
time was tricky, but reduced downtime. ATE would have been a marginal
failure had I not been able to "borrow" test equipment from the
engineering dept.

However, that was production test, not troubleshooting. When the
manual or ATE test line declared something worthy of troubleshooting,
it was NOT done while there were units waiting to be tested. If the
products were cheap enough, they could just be "remanufactured" which
means tear them apart down to the board level, run them back through
board test, and build a "new" unit. This worked well with radios that
had plugin cards. Eventually, there was a backlog of boards to be
troubleshot. Usually between production runs and contracts, someone
would decide that it's time to clean up the backlog. However, instead
of having the test techs do the troubleshooting, the engineer who
designed the radio would be sentence to overtime diagnosing the
boards. Yeah, that was usually me. Unless the problem was trivial, I
would only tag the likely parts, borrow someone that could do the
soldering, retest the board, and send it on to production test. This
worked well when we needed 25 identical board immediately, and was a
total waste of time for 5 or less boards that took too long to setup.

Today, much of what I see is ATE run by techs that only know how to
push the buttons. Troubleshooting is done partly with BITE (built in
test equipment). Parts replacement and soldering is outsourced to a
contractor, specialty shop, or refurbisher. In short, there's nobody
on the production line that knows which end of the soldering iron to
grab, much less how the product actually works. The rule is that
production must continue unimpeded by any form of troubleshooting or
repair. If there is any troubleshooting, it's to fix the production
line and ATE, not the actual product.

Might as well say something about bugs and fixes. With todays fairly
short product lives (typically about 6 months), it's not uncommon for
a company to have 3 or 4 generations of replacement products in
development at the same time. If something is found lacking or
defective in the current product, it is cheaper and easier to simply
wait for the next model to appear in production, and replace it with a
later version. What this means is that NOTHING gets fixed in
production, even when it's a known problem, easy fix, or major
enhancement. If you see products with known design flaws that
continue to be manufactured with the flaws, you now know why.
http://www.designnews.com/archives.asp?section_id=1367

Of course, there will still be independent repair shops (like mine)
that fix things one at a time. They're a dying breed mostly because
of the declining cost of modern electronics. As the retail price of
new hardware declines, the amount of money that a customer is willing
to pay for a repair also declines. As a rule-of-thumb, most customers
will buy a new replacment instead of repairing something when the
repair cost exceeds 50% of the replacement cost. So, if someone drags
in an out of warranty laptop that cost them $500 about 3 years ago, my
maximum bill (parts+labor) cannot exceed $250. Assuming no parts were
replaced, that 3.3 hrs at $75/hr. The number of things I can fix in
under 3.3 hrs is rapidly shrinking. For example, I have an APC XS1300
UPS on the bench that can be purchased new for about $125. In order
to replace one lousy bulging electrolytic capacitor, I've already
burned 2 hrs and I'm not done. Can I bill the customer $150 to fix a
$125 UPS? Nope.

So, the question isn't as much how to troubleshoot, but whether it's
worth you time troubleshooting in the first place.

Happy end of the tax year.



--
Jeff Liebermann
150 Felker St #D
http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558


Sounds like you touched a lot of bases in the service life. I took a similar path ending up self employed for about the last 25 years. It has changed so much from the old days walking around with a tube caddy cleaning TV tuners. I now walk around with a laptop pinging IP addresses. How did that happen? I think the writing is on the wall. How many shoe repair and watch repair shops do you see. The electronic repair tech could meet the same fate. Just the other day I saw a flat screen monitor sitting in a garbage bin. To see the rain falling on it was too much so I took it inside. When I plugged it in everything worked and it had a VGA plus DVI input! What was that doing in the garbage. My only guess is someone wanted a wider flatter monitor so he or she tossed it out. I am typing on that monitor as we speak. How can one make a living in service with this going on. It is so bad that I have to work on 50,000 dollar LED displays boards. They will still fix those at that price. Just abou

t everything else is disposable. However I have no regrets as electronics has been an existing ride with technology changing so fast that there is never a dull moment.


There is always arcade game repair. There is enough interest in that
that most cities need a few people who do house calls.

John :-#)#

--
(Please post followups or tech inquiries to the USENET newsgroup)
John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9
(604)872-5757 or Fax 872-2010 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."


I noted you are from Vancouver. I grew up there until about 14 then Montreal and now Toronto. Fond memories of biking down to Kitsilano beach.
  #18   Report Post  
Old January 2nd 16, 02:40 AM posted to sci.electronics.repair
external usenet poster
 
First recorded activity by DIYBanter: Nov 2013
Posts: 221
Default Diffferent techniques in troubleshooting

I'm a mechanical engineer but I've been in management a long time, I don't get to do much technical stuff.

This week I got called to a gas leak. The emergency response and the mechanics had already been there and confirmed safe to reoccupy, but somebody wasn't so sure and called me.

These things are 80% one problem and 9% the other. The crew that showed up found and fixed the 80% problem, but it wasn't actually causing the leak. The leak was somewhere else. Just because one thing is broken doesn't mean something else isn't broken too.

Once a problem is identified, attentional blindness sets in. Contrary evidence is not just ignored, it cannot be seen.

In this case the pilot light was out in the kitchen, and they assumed the gas smell came from it. They shut off the gas to the kitchen and authorized the building to be reoccupied.

They ignored the evidence the real leak was somewhere else - well, they were incapable of seeing that evidence because they already knew what was wrong.

When I got on scene it took little time to find where the smell was coming from. Partly that's from my bias to try to avoid assigning the cause until I've looked at all the evidence, but partly it's from knowing human nature and knowing if it were the usual problem they would have fixed it the first time, and it obviously wasn't.

I sent the mechanics back and told them where to look, and the second trip they fixed it correctly. Of course I had to keep quiet my part in it, there's always politics in these things.

So yes, fix the most likely fault first, but bear in mind the potential cost of it being something else.
  #19   Report Post  
Old January 2nd 16, 05:55 AM posted to sci.electronics.repair
external usenet poster
 
First recorded activity by DIYBanter: Dec 2015
Posts: 41
Default Diffferent techniques in troubleshooting

On Friday, January 1, 2016 at 9:41:01 PM UTC-5, Tim R wrote:
I'm a mechanical engineer but I've been in management a long time, I don't get to do much technical stuff.

This week I got called to a gas leak. The emergency response and the mechanics had already been there and confirmed safe to reoccupy, but somebody wasn't so sure and called me.

These things are 80% one problem and 9% the other. The crew that showed up found and fixed the 80% problem, but it wasn't actually causing the leak.. The leak was somewhere else. Just because one thing is broken doesn't mean something else isn't broken too.




Once a problem is identified, attentional blindness sets in. Contrary evidence is not just ignored, it cannot be seen.

In this case the pilot light was out in the kitchen, and they assumed the gas smell came from it. They shut off the gas to the kitchen and authorized the building to be reoccupied.

They ignored the evidence the real leak was somewhere else - well, they were incapable of seeing that evidence because they already knew what was wrong.

When I got on scene it took little time to find where the smell was coming from. Partly that's from my bias to try to avoid assigning the cause until I've looked at all the evidence, but partly it's from knowing human nature and knowing if it were the usual problem they would have fixed it the first time, and it obviously wasn't.

I sent the mechanics back and told them where to look, and the second trip they fixed it correctly. Of course I had to keep quiet my part in it, there's always politics in these things.

So yes, fix the most likely fault first, but bear in mind the potential cost of it being something else.


I hear that. I remember being stuck on a problem so I asked a friend for a fresh look at it. He looks around then thought about it for a minute. He then looked at me and said " if you touch your head and it hurts and you touch you arm and it hurts and you touch your toe and it hurts maybe it is your finger that is the problem ". That was a strange way to put it but he was 100 percent right as I had my scope probe on 1 to 1 instead of 10 to 1 causing a loading problem. It is always a good idea to get a second opinion when you are spinning your wheels.

Another unrelated problem. You being an engineer will enjoy this one. The city has a water leak. They are not sure where the leak is. They can not dig up a whole city block to find it so they use a clever trick. They put two microphones about 50 feet apart where the leak seems to be. Then then record the random sound of water hissing out of the pipe. The two microphones are wired to left and right channel of the recorder. By adjusting the time delay of the right or left microphone they can find the sweet spot where the random noise from one microphone matches the random noise of the other microphone. Once the delay is know they know where the leak is within 1 or 2 feet. That is a clever trick.

There is a similar trick in cabling. You send a pulse down a cable that is about 80 percent c propagation speed. If you hear an echo you have a problem. By timing the echo at 80 percent c you know where the problem is.
  #20   Report Post  
Old January 2nd 16, 07:04 AM posted to sci.electronics.repair
external usenet poster
 
First recorded activity by DIYBanter: Jun 2012
Posts: 1,635
Default Diffferent techniques in troubleshooting

"Another unrelated problem. You being an engineer will enjoy this one. The city has a water leak. They are not sure where the leak is. They can not dig up a whole city block to find it so they use a clever trick. They put two microphones about 50 feet apart where the leak seems to be. Then then record the random sound of water hissing out of the pipe. The two microphones are wired to left and right channel of the recorder. By adjusting the time delay of the right or left microphone they can find the sweet spot where the random noise from one microphone matches the random noise of the other microphone. Once the delay is know they know where the leak is within 1 or 2 feet. That is a clever trick. "

HA, HAHAHAHAHAH

HydroTDR

Water Domain reflectometry

Feel free to add your own, this could be fun. Water Wave Technology.

Oh, and sound is so much faster in water, but then that gives alot more accurate transmission, which os probably necessary to make this possible.

WDR. Water Domain Reflectometerty.

Yeah fukit


Reply
Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules

Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
joinery techniques Electric Comet Woodworking 12 May 13th 15 06:29 PM
old techniques still in use? David Harmon Metalworking 0 May 1st 08 11:07 PM
old techniques still in use? Wes[_2_] Metalworking 1 May 1st 08 02:31 AM
old techniques still in use? Wes[_2_] Metalworking 0 April 30th 08 10:06 PM
Polishing techniques Frederic Elias Woodworking 3 April 30th 04 05:44 PM


All times are GMT +1. The time now is 02:18 PM.

Powered by vBulletin® Copyright ©2000 - 2019, Jelsoft Enterprises Ltd.
Copyright 2004-2019 DIYbanter.
The comments are property of their posters.
 

About Us

"It's about DIY & home improvement"

 

Copyright © 2017