| Author |
Message |
N Cook
Guest
|
 Posted:
Thu Feb 10, 2005 12:15 am Post subject:
Repair Tech's strangest fault situations |
|
|
Anyone else's contributions.
I was reveiwing my collection of test kit repair breifs and
re-read this one
"Eventually found ( problem with 'scope power supply )
the O/P was being loaded by a faulty opto-isolator that
gates the beam current. It was ohmic between I/P
and O/P so removed and cracked open with mole grips
(vice grip locking pliers). Looking at the transparent
bridge under a 30x microscope there were tiny circles of
mold or fungus that had grown and coalesced forming
a resistive bridge between I/P and O/P."
While on the theme. Has anyone else come
across old kit with conformal coating over everything
that appears to have chemically broken down to an oily
consistency that then seeps into ICs corrupting them
electronic hints and repair briefs , schematics/manuals list on
http://homepages.tcp.co.uk/~diverse
test kit repairs file
http://www.divdev.fsnet.co.uk/repair4.htm
|
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RonKZ650@aol.com
Guest
|
| Posted:
Thu Feb 10, 2005 1:53 am Post subject:
Re: Repair Tech's strangest fault situations |
|
|
I've worked on a few sets filled with dead cockroaches. I always
thought it would be great to be able to tell the customer when they ask
"What was wrong with it" to truthfully say "Cockroaches were all over
in there and shorted out the electronics". Unfortunately removal of
dead roaches never actually helped fix any of these sets :-( |
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Sam Goldwasser
Guest
|
| Posted:
Thu Feb 10, 2005 1:57 am Post subject:
Re: Repair Tech's strangest fault situations |
|
|
"RonKZ650@aol.com" <RonKZ650@aol.com> writes:
| Quote: | I've worked on a few sets filled with dead cockroaches. I always
thought it would be great to be able to tell the customer when they ask
"What was wrong with it" to truthfully say "Cockroaches were all over
in there and shorted out the electronics". Unfortunately removal of
dead roaches never actually helped fix any of these sets :-(
|
Sure, but the cockroaches may have shorted out the power supplies causing
other parts to fail. :)
--- sam | Sci.Electronics.Repair FAQ Mirror: http://repairfaq.ece.drexel.edu/
Repair | Main Table of Contents: http://repairfaq.ece.drexel.edu/REPAIR/
+Lasers | Sam's Laser FAQ: http://repairfaq.ece.drexel.edu/sam/lasersam.htm
| Mirror Sites: http://repairfaq.ece.drexel.edu/REPAIR/F_mirror.html
Note: These links are hopefully temporary until we can sort out the excessive
traffic on Repairfaq.org.
Important: Anything sent to the email address in the message header above is
ignored unless my full name is included in the subject line. Or, you can
contact me via the Feedback Form in the FAQs.
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N Cook
Guest
|
| Posted:
Thu Feb 10, 2005 2:25 am Post subject:
Re: Repair Tech's strangest fault situations |
|
|
<RonKZ650@aol.com> wrote in message
news:1107978809.188283.3810@l41g2000cwc.googlegroups.com...
| Quote: | I've worked on a few sets filled with dead cockroaches. I always
thought it would be great to be able to tell the customer when they ask
"What was wrong with it" to truthfully say "Cockroaches were all over
in there and shorted out the electronics". Unfortunately removal of
dead roaches never actually helped fix any of these sets :-(
|
http://en.wikipedia.org/wiki/Computer_bug
The First Computer Bug
In 1946, when Hopper was released from active duty, she joined the Harvard
Faculty at the Computation Laboratory where she continued her work on the
Mark II and Mark III. Operators traced an error in the Mark II to a moth
trapped in a relay, coining the term bug. This bug was carefully removed and
taped to the log book September 9th 1945. Hopper recounted the cause to be
an actual insect stuck between the contacts of a relay in the logic
mechanisms of the device.
electronic hints and repair briefs , schematics/manuals list on
http://homepages.tcp.co.uk/~diverse |
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|
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Art
Guest
|
| Posted:
Thu Feb 10, 2005 2:56 am Post subject:
Re: Repair Tech's strangest fault situations |
|
|
Worked in a repair shop that did a lot of service for K-Mart, on their
Televisions and VCRs. Received one VCR that had a strange aroma when
attempting to get near enough to service it, after finally removing the top
and checking the load mechanism it was found to contain a half eaten "Green
(At least after the shipping period) Peanut Butter and Jelly Sandwich". Unit
was placed into a Black Garbage Bag, Placed into a box, and returned to the
K-Mart Store with a statement to the fact that removal of customer loaded
debris into the mechanism is not a warranty payable failure.
A couple of months ago went on a service call regarding the failure of a
customers Toshiba 61" Projection TV. Arrived on site and met the husband and
wife, began inspecting the set and asked the husband to assist me in moving
the set away from the wall. Upon looking at the back panel of the set I
asked them if they had any animals that spent a lot of time behind the set.
The wife charms in, oh yah, the tom cat is always back there. The husband
looks and asks me why the back panel from about 10" down to the floor level
seems to be a rather yellow colour rather than the pastel brown of the
pasteboard.
I removed the back panel to find mold and partially dried cat urine sprayed
almost half way across the chassis. The customer questioned about the
special deal they got on the extended warranty that the "Salesman said
covers everything"??
Well, I commented, The salesman obviously does not keep cats as pets and
this type of damage definitely is not covered by any warranty. However, I
will pass on charging you the service call charge if you allow me to repeat
this story many times.
"N Cook" <diverse2@tcp.co.antyspahm.uk> wrote in message
news:v5GdnQLY8bSZ75ffRVn-tg@tcp.co.uk...
| Quote: | RonKZ650@aol.com> wrote in message
news:1107978809.188283.3810@l41g2000cwc.googlegroups.com...
I've worked on a few sets filled with dead cockroaches. I always
thought it would be great to be able to tell the customer when they ask
"What was wrong with it" to truthfully say "Cockroaches were all over
in there and shorted out the electronics". Unfortunately removal of
dead roaches never actually helped fix any of these sets :-(
http://en.wikipedia.org/wiki/Computer_bug
The First Computer Bug
In 1946, when Hopper was released from active duty, she joined the Harvard
Faculty at the Computation Laboratory where she continued her work on the
Mark II and Mark III. Operators traced an error in the Mark II to a moth
trapped in a relay, coining the term bug. This bug was carefully removed
and
taped to the log book September 9th 1945. Hopper recounted the cause to be
an actual insect stuck between the contacts of a relay in the logic
mechanisms of the device.
electronic hints and repair briefs , schematics/manuals list on
http://homepages.tcp.co.uk/~diverse
|
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|
| Back to top |
|
|
BOB URZ
Guest
|
| Posted:
Thu Feb 10, 2005 5:47 am Post subject:
Re: Repair Tech's strangest fault situations |
|
|
N Cook wrote:
| Quote: | Anyone else's contributions.
I was reveiwing my collection of test kit repair breifs and
re-read this one
"Eventually found ( problem with 'scope power supply )
the O/P was being loaded by a faulty opto-isolator that
gates the beam current. It was ohmic between I/P
and O/P so removed and cracked open with mole grips
(vice grip locking pliers). Looking at the transparent
bridge under a 30x microscope there were tiny circles of
mold or fungus that had grown and coalesced forming
a resistive bridge between I/P and O/P."
While on the theme. Has anyone else come
across old kit with conformal coating over everything
that appears to have chemically broken down to an oily
consistency that then seeps into ICs corrupting them
electronic hints and repair briefs , schematics/manuals list on
http://homepages.tcp.co.uk/~diverse
test kit repairs file
http://www.divdev.fsnet.co.uk/repair4.htm
|
Was working on a old hitachi VCR once. The mech control buttons
were messed up. Some did nothing at all while the others did functions
other than what they said. That was a real puzzler. This keypad used a
resistor matrix for a voltage divider to determine which key was
pressed. Upon closer inspection, a hard sugary material was found on the
circuit board. Turned out someone spilled oatmeal with plenty of sugar
on it into the vent holes on the top of the unit. This dripped down on
the circuit board by where the front panel plugged in. The crystallized
sugar added enough resistance to screw up the function by added
additional resistance to the lines to ground.
I had a car stereo amp once which had voltage on the ground of the RCA
input jacks. i had the unit on the bench with a AC powered
cassette deck as a source and all was fine. All rail voltages were
OK. But when you hooked up a car stereo type input on the same 12 volt
ground things would spark and wack out. Turned out the torroid
switching transformer was shorting out a primary winding to the
shield below which was a shield for the secondary low volt supplies.
The end result was this effectively put 12 volts on the shield of the
RCA input jacks. Lifting the torroid and a well placed insulator over
the nicked winding solved the problem.
Bob
----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==----
http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups
----= East and West-Coast Server Farms - Total Privacy via Encryption =---- |
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Deke
Guest
|
| Posted:
Thu Feb 10, 2005 8:41 am Post subject:
Re: Repair Tech's strangest fault situations |
|
|
<RonKZ650@aol.com> wrote in message
news:1107978809.188283.3810@l41g2000cwc.googlegroups.com...
| Quote: | I've worked on a few sets filled with dead cockroaches. I always
thought it would be great to be able to tell the customer when they ask
"What was wrong with it" to truthfully say "Cockroaches were all over
in there and shorted out the electronics". Unfortunately removal of
dead roaches never actually helped fix any of these sets :-(
|
You mean you actually go ahead and work on them?
Our SOP is to put them in a large garbage bag, spay a bunch of RAID in the
bag, then seal the bag. We then call the customer and tell them we cant
work on it because its full of roaches, we dont want to infect our shop, and
please come and get the unit. Its given to them, still in the bag, and they
are advised not to bring it back. Cheaper to refuse the service, than to
infect your shop, and have to fumigate. |
|
| Back to top |
|
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Leonard Caillouet
Guest
|
| Posted:
Thu Feb 10, 2005 5:56 pm Post subject:
Re: Repair Tech's strangest fault situations |
|
|
"Deke" <no spam@today.com> wrote in message
news:qvAOd.269$n7.156@fe25.usenetserver.com...
| Quote: |
RonKZ650@aol.com> wrote in message
news:1107978809.188283.3810@l41g2000cwc.googlegroups.com...
I've worked on a few sets filled with dead cockroaches. I always
thought it would be great to be able to tell the customer when they ask
"What was wrong with it" to truthfully say "Cockroaches were all over
in there and shorted out the electronics". Unfortunately removal of
dead roaches never actually helped fix any of these sets :-(
You mean you actually go ahead and work on them?
Our SOP is to put them in a large garbage bag, spay a bunch of RAID in
the
bag, then seal the bag. We then call the customer and tell them we cant
work on it because its full of roaches, we dont want to infect our shop,
and
please come and get the unit. Its given to them, still in the bag, and
they
are advised not to bring it back. Cheaper to refuse the service, than to
infect your shop, and have to fumigate.
|
You are kidding, right?
Leonard
> |
|
| Back to top |
|
|
Deke
Guest
|
| Posted:
Thu Feb 10, 2005 8:03 pm Post subject:
Re: Repair Tech's strangest fault situations |
|
|
"Leonard Caillouet" <no@no.com> wrote in message
news:FfIOd.56446$jn.2086@lakeread06...
| Quote: |
"Deke" <no spam@today.com> wrote in message
news:qvAOd.269$n7.156@fe25.usenetserver.com...
RonKZ650@aol.com> wrote in message
news:1107978809.188283.3810@l41g2000cwc.googlegroups.com...
I've worked on a few sets filled with dead cockroaches. I always
thought it would be great to be able to tell the customer when they
ask
"What was wrong with it" to truthfully say "Cockroaches were all over
in there and shorted out the electronics". Unfortunately removal of
dead roaches never actually helped fix any of these sets :-(
You mean you actually go ahead and work on them?
Our SOP is to put them in a large garbage bag, spay a bunch of RAID in
the
bag, then seal the bag. We then call the customer and tell them we cant
work on it because its full of roaches, we dont want to infect our shop,
and
please come and get the unit. Its given to them, still in the bag, and
they
are advised not to bring it back. Cheaper to refuse the service, than
to
infect your shop, and have to fumigate.
You are kidding, right?
Leonard
Not at all. Are you saying you like working on stuff full of roaches? We |
dont, and wont. |
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|
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J. Doe
Guest
|
| Posted:
Thu Feb 10, 2005 9:07 pm Post subject:
Re: Repair Tech's strangest fault situations |
|
|
Deke wrote:
| Quote: |
You are kidding, right?
Leonard
Not at all. Are you saying you like working on stuff full of
roaches? We dont, and wont.
|
I had the same experience with a CB radio. Took the lid off on the work
bench and couldn't believe what I saw! It looked like a bowl of cereal,
only most of the corn flakes were alive! About the time they realized it
was freedom, several took off across the bench before I slammed the lid back
on, took it outside and hit it with bug spray, put it in a sealed bag, and
returned it to the customer with the warning - DO NOT open this in your
house or car. How the roaches got in there in the first place is amazing,
since the only opening was the 1/8" speaker jack. A couple of baby roaches
must have went in that way and set up house. Can't believe they actually
muliplied to the point of no more space, with no food or water....... |
|
| Back to top |
|
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N Cook
Guest
|
| Posted:
Fri Feb 11, 2005 12:07 am Post subject:
Re: Repair Tech's strangest fault situations |
|
|
"Art" <plotsligt@comcast.net> wrote in message
news:2didnffIqPB05ZffRVn-2A@comcast.com...
| Quote: | Worked in a repair shop that did a lot of service for K-Mart, on their
Televisions and VCRs. Received one VCR that had a strange aroma when
attempting to get near enough to service it, after finally removing the
top
and checking the load mechanism it was found to contain a half eaten
"Green
(At least after the shipping period) Peanut Butter and Jelly Sandwich".
Unit
was placed into a Black Garbage Bag, Placed into a box, and returned to
the
K-Mart Store with a statement to the fact that removal of customer loaded
debris into the mechanism is not a warranty payable failure.
A couple of months ago went on a service call regarding the failure of a
customers Toshiba 61" Projection TV. Arrived on site and met the husband
and
wife, began inspecting the set and asked the husband to assist me in
moving
the set away from the wall. Upon looking at the back panel of the set I
asked them if they had any animals that spent a lot of time behind the
set.
The wife charms in, oh yah, the tom cat is always back there. The husband
looks and asks me why the back panel from about 10" down to the floor
level
seems to be a rather yellow colour rather than the pastel brown of the
pasteboard.
I removed the back panel to find mold and partially dried cat urine
sprayed
almost half way across the chassis. The customer questioned about the
special deal they got on the extended warranty that the "Salesman said
covers everything"??
Well, I commented, The salesman obviously does not keep cats as pets and
this type of damage definitely is not covered by any warranty. However, I
will pass on charging you the service call charge if you allow me to
repeat
this story many times.
"N Cook" <diverse2@tcp.co.antyspahm.uk> wrote in message
|
Remembered another strange fault.
Car tape player, so no record function, but every tape
that was played in it got an overlaid recording
of the click you get with a vinyl LP playing at 33 rpm.
Permanently recorded on commercial tapes that
had the 'write protect' tabs activated. Play the tapes on
any other machine and the clicks were permanently there.
I'll leave that as a teaser , in case anyone can
fathom the fault, before I reveal tomorrow.
electronic hints and repair briefs , schematics/manuals list on
http://homepages.tcp.co.uk/~diverse |
|
| Back to top |
|
|
Guest
|
| Posted:
Fri Feb 11, 2005 1:30 am Post subject:
Re: Repair Tech's strangest fault situations |
|
|
| Quote: | Remembered another strange fault.
Car tape player, so no record function, but every tape
that was played in it got an overlaid recording
of the click you get with a vinyl LP playing at 33 rpm.
Permanently recorded on commercial tapes that
had the 'write protect' tabs activated. Play the tapes on
any other machine and the clicks were permanently there.
I'll leave that as a teaser , in case anyone can
fathom the fault, before I reveal tomorrow.
electronic hints and repair briefs , schematics/manuals list on
http://homepages.tcp.co.uk/~diverse
That would have to be a small magnet that had gotten inside on some
rotating part, or a rotating part had became magnetized, that contacts or |
goes near the tape.
MVB |
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|
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that parrot chap
Guest
|
| Posted:
Fri Feb 11, 2005 2:37 am Post subject:
Re: Repair Tech's strangest fault situations |
|
|
On Thu, 10 Feb 2005 18:07:10 -0000, "N Cook"
<diverse2@tcp.co.antyspahm.uk> wrote:
| Quote: | "Art" <plotsligt@comcast.net> wrote in message
news:2didnffIqPB05ZffRVn-2A@comcast.com...
Worked in a repair shop that did a lot of service for K-Mart, on their
Televisions and VCRs. Received one VCR that had a strange aroma when
attempting to get near enough to service it, after finally removing the
top
and checking the load mechanism it was found to contain a half eaten
"Green
(At least after the shipping period) Peanut Butter and Jelly Sandwich".
Unit
was placed into a Black Garbage Bag, Placed into a box, and returned to
the
K-Mart Store with a statement to the fact that removal of customer loaded
debris into the mechanism is not a warranty payable failure.
A couple of months ago went on a service call regarding the failure of a
customers Toshiba 61" Projection TV. Arrived on site and met the husband
and
wife, began inspecting the set and asked the husband to assist me in
moving
the set away from the wall. Upon looking at the back panel of the set I
asked them if they had any animals that spent a lot of time behind the
set.
The wife charms in, oh yah, the tom cat is always back there. The husband
looks and asks me why the back panel from about 10" down to the floor
level
seems to be a rather yellow colour rather than the pastel brown of the
pasteboard.
I removed the back panel to find mold and partially dried cat urine
sprayed
almost half way across the chassis. The customer questioned about the
special deal they got on the extended warranty that the "Salesman said
covers everything"??
Well, I commented, The salesman obviously does not keep cats as pets and
this type of damage definitely is not covered by any warranty. However, I
will pass on charging you the service call charge if you allow me to
repeat
this story many times.
"N Cook" <diverse2@tcp.co.antyspahm.uk> wrote in message
Remembered another strange fault.
Car tape player, so no record function, but every tape
that was played in it got an overlaid recording
of the click you get with a vinyl LP playing at 33 rpm.
Permanently recorded on commercial tapes that
had the 'write protect' tabs activated. Play the tapes on
any other machine and the clicks were permanently there.
I'll leave that as a teaser , in case anyone can
fathom the fault, before I reveal tomorrow.
electronic hints and repair briefs , schematics/manuals list on
http://homepages.tcp.co.uk/~diverse
|
bit of metal or shredded magnetic oxide embedded in the pinch roller??
> |
|
| Back to top |
|
|
Guest
|
| Posted:
Fri Feb 11, 2005 5:36 am Post subject:
Re: Repair Tech's strangest fault situations |
|
|
N Cook wrote:
| Quote: | Remembered another strange fault.
Car tape player, so no record function, but every tape
that was played in it got an overlaid recording
of the click you get with a vinyl LP playing at 33 rpm.
Permanently recorded on commercial tapes that
had the 'write protect' tabs activated. Play the tapes on
any other machine and the clicks were permanently there.
I'll leave that as a teaser , in case anyone can
fathom the fault, before I reveal tomorrow.
|
A click rather than partial erasure?
racked my brains, all I can think of is:
- something metallic in contact with the capstan/pinch roller
- some kind of spool motion sensor magnet got shifted out of place????
- head leads somehow got shifted near something like an intermittent
solenoid, induced current into them/ picked up strong parasitic
signals???? (cue sound of scraping of bottom of barrel)
-B |
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|
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N Cook
Guest
|
| Posted:
Fri Feb 11, 2005 1:46 pm Post subject:
Re: Repair Tech's strangest fault situations |
|
|
Two brownie points to this person.
The weird thing was the noise was exactly like the click
from a deep scratch on a vinyl record and similar
repeat rate , come to think about it, 45 rpm.
"that parrot chap" <kev@somewhere.in.the.uk> wrote in message
news:8ehn01d2v39mvqbmv4cd9mj2mv50geev9b@4ax.com...
| Quote: | On Thu, 10 Feb 2005 18:07:10 -0000, "N Cook"
diverse2@tcp.co.antyspahm.uk> wrote:
"Art" <plotsligt@comcast.net> wrote in message
news:2didnffIqPB05ZffRVn-2A@comcast.com...
Worked in a repair shop that did a lot of service for K-Mart, on their
Televisions and VCRs. Received one VCR that had a strange aroma when
attempting to get near enough to service it, after finally removing the
top
and checking the load mechanism it was found to contain a half eaten
"Green
(At least after the shipping period) Peanut Butter and Jelly Sandwich".
Unit
was placed into a Black Garbage Bag, Placed into a box, and returned to
the
K-Mart Store with a statement to the fact that removal of customer
loaded
debris into the mechanism is not a warranty payable failure.
A couple of months ago went on a service call regarding the failure of
a
customers Toshiba 61" Projection TV. Arrived on site and met the
husband
and
wife, began inspecting the set and asked the husband to assist me in
moving
the set away from the wall. Upon looking at the back panel of the set I
asked them if they had any animals that spent a lot of time behind the
set.
The wife charms in, oh yah, the tom cat is always back there. The
husband
looks and asks me why the back panel from about 10" down to the floor
level
seems to be a rather yellow colour rather than the pastel brown of the
pasteboard.
I removed the back panel to find mold and partially dried cat urine
sprayed
almost half way across the chassis. The customer questioned about the
special deal they got on the extended warranty that the "Salesman said
covers everything"??
Well, I commented, The salesman obviously does not keep cats as pets
and
this type of damage definitely is not covered by any warranty. However,
I
will pass on charging you the service call charge if you allow me to
repeat
this story many times.
"N Cook" <diverse2@tcp.co.antyspahm.uk> wrote in message
Remembered another strange fault.
Car tape player, so no record function, but every tape
that was played in it got an overlaid recording
of the click you get with a vinyl LP playing at 33 rpm.
Permanently recorded on commercial tapes that
had the 'write protect' tabs activated. Play the tapes on
any other machine and the clicks were permanently there.
I'll leave that as a teaser , in case anyone can
fathom the fault, before I reveal tomorrow.
electronic hints and repair briefs , schematics/manuals list on
http://homepages.tcp.co.uk/~diverse
bit of metal or shredded magnetic oxide embedded in the pinch roller??
|
|
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|
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|
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