Golden Rules of Troubleshooting

On Mon, 14 Dec 2015 14:05:17 -0000 (UTC), Cursitor Doom
<curd@notformail.com> wrote:

Anyone care to share their experience on the correct approach to
troubleshooting? I'll kick off by suggesting:

1. Assume nothing.

Perhaps we can assemble a list of golden rules....

There is no correct approach. There are only approaches that work
under specific circumstances. Like the universal solution to all
problems, and the answer to all questions (42), the correct approach
are only useful after you found the solution.

1. That which you know to be functional, beyond any need of checking,
is usually the problem.

2. Solutions found after midnight are best forgotten as they are
likely to be the product of temporary insanity.

3. Things go better if you have a schematic, gallon of coffee, a
working unit to compare, and a parts unit to cannibalize.

4. While it is theoretically possible to work on two problems at one
time, it is much easier to fix problems in the order they appear. I
like to fix the little things first.

5. Nothing is considered fixed until after it is cleaned. If you
can't fix it, at least make it look like it's been fixed.

6. Approximately half the disassembly videos on YouTube are wrong,
useless, dangerous, or out of focus.

7. For a good collection of counterfeit parts, just buy them on eBay.

8. Your most valuable tool is a visual inspection, often with a
magnifying glass. This helps identify exploded, incinerated, or
overheated components. It also shows where the previous repairs were
performed, a sure sign of problems to come.

9. Always ignore the symptoms and theories of the customer. They're
often misleading and will usually waste your time chasing down false
theories. Test the unit yourself to confirm the symptoms. I often
find a very different set of problems or that the buzzwords in the
original description were misused.

10. Fix everything that you find, even if the customer hasn't
complained about it. If it's wrong, even slightly, they'll be back to
complain and you might end up fixing it for free.

11. Take photographs of before and after. Treat is as if it were
evidence in a lawsuit or insurance investigation. I also take a photo
of the insides of the customers laptop, and use it for wallpaper on
their desktop. The reactions are "interesting" and help fortify my
exorbitant rates. The photos also help when I can't recall how to put
it back together.

12. Never do what cannot be undone. For computahs, make an image
backup of the hard disk both before and after the repair. Image
backup programs are now very fast and Terabyte USB 3.0 hard disk
drives are cheap.

13. No repair is complete without a culprit. The first step to doing
a repair is to blame someone or something. This is an important part
of the repair as most customers are worried that they may have done
something wrong (such as buying a piece of junk). By blaming someone
else, this eases their guilty conscience.

14. Never let the customer see you reading the instruction manual.
They will immediately suspect that you don't know what you're doing.

15. Beware of spare parts left over after reassembly.

More later. I'm late (as usual).

--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
 
Ken <Ken@invalid.com> wrote:
Phil Allison wrote:
Cursitor Doom wrote:


Anyone care to share their experience on the correct approach to
troubleshooting? I'll kick off by suggesting:

1. Assume nothing.

Perhaps we can assemble a list of golden rules....



** Troubleshooting is like a maze, there are many starting points and
blind alleys to negotiate on your the way to the goal.

Unfamiliar equipment requires a more cautious approach than familiar
items.

Always observe the fault carefully *before* starting disassembly and
find out what functions work and what do not.

Owner's descriptions are often misleading or fail to mention
important issues, but you still need to find out what prompted that
description.

Bench tests need to simulate actual use or worst case use, but beware
of simulating abuse.

When stuck on a problem, take a break and start over a day or so
later.




.... Phil


"When stuck on a problem, take a break and start over a day or so
later." I cannot tell you how many problems I solved while doing that.
Sometimes getting just getting away from the problem allows clearer
thought.

I've stared at well written service manuals (these actually exist, but
tend to be old) that just made no sense until the next day, or after a
break. Not a fan of touching service manuals with diry hands either.
 
Tim R <timothy42b@aol.com> wrote:
Most important, assume nothing. As soon as you think you know what is wrong, it is impossible not to ignore contrary evidence.

I work with some engineers who are good designers because they keep their brain fixed on the goal and work through every obstacle. They THINK they are also good troubleshooters but they are wrong, obstinately frustratingly wrong, for the same reason. They KNOW what is wrong too early, and nothing shakes their belief.

Second. When anybody tells you the symptoms, listen. When they tell you why, STOP! Don't listen. It will probably be theoretically impossible, and then you end up doubting the symptoms. Sorry but this is especially a problem with techs and mechanics. They observe correctly but theorize contrary to the laws of physics, so you need to stop listening when they get to that point.

I helps to try to figure out what a device should do when it is working.
Extracting this information is sometimes really hard when people are
fixating on what's broken and keep talking in circles.
 
On 12/15/2015 10:16 AM, Cursitor Doom wrote:
On Tue, 15 Dec 2015 07:37:42 -0800, John Robertson wrote:

I must confess we do replace almost all electrolytic caps that are more
than about 30 years old in our vintage game monitors and amplifiers
(video/pinball/jukebox) as this saves a tremendous amount of
troubleshooting time.

Does it, though? I mean, you could save even more time by just running
all the caps through an ESR meter test and just replacing those that
fail. Given how fragile some of those old PCB traces can be, I'd only
want to replace the caps that really way out of spec.

Um, we use temperature controlled soldering irons and the traces on most
of our arcade grade games stand several soldering cycles...

The Bob Parker design ESR meter (which we've been selling since 1999)
doesn't handle small value caps (under 10UFD) very well, and on the
monitors a bunch are 4.7ufd or less.

There are only about fifteen caps in the average monitor, and it takes
about an hour to pull the chassis, replace the caps, do the ring/LOPT
test, check the fuse, reinstall and start the burn-in process. Then it
goes away for five to ten years.

Amps can be worse, particularly early stereo tube amps where all the
parts are connected on standoffs - those can take three to five hours to
recap. They don't come back for ten to twenty years after a recap and
resistor check (tubes too of course).

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."
 
Jeff Liebermann wrote:


3. Things go better if you have a schematic, gallon of coffee, a
working unit to compare, and a parts unit to cannibalize.

Oh wow! This one is up there with Murphy's law!

And, unless you are the manufacturer of said device, much of the above will
never be available.

Jon
 
"Cydrome Leader" <presence@MUNGEpanix.com> wrote in message
news:n4q6qt$2tt$2@reader1.panix.com...
I helps to try to figure out what a device should do when it is working.
Extracting this information is sometimes really hard when people are
fixating on what's broken and keep talking in circles.

I got a call at the plant I worked at from an equipment operator. When I
got there he said an indicator light would not come on. He had changed
bulbs and even swappend a glowing one with the one that would not come on to
show me it was not the bulb.

I asked him about the equipment as I did not know anything about it. He
said he presses one button and a light comes on , then he presses the second
button and another light comes on, but now the second light would not come
on. As this was just in a control room and the equipment could be located
anywhere in the plant I asked him several times about the equipment and all
I could get out of him was he just pressse the buttons and the lights should
come. He did not seem to know where the equipment was, just the indicator
lights..
 
On Tue, 15 Dec 2015 15:49:13 -0600, Jon Elson <jmelson@wustl.edu>
wrote:

Jeff Liebermann wrote:

3. Things go better if you have a schematic, gallon of coffee, a
working unit to compare, and a parts unit to cannibalize.

Oh wow! This one is up there with Murphy's law!

And, unless you are the manufacturer of said device, much of the above will
never be available.

Gallons of coffee are available at your local supermarket.

I practice what I preach. If really want something to work, I buy 3
of them, and cannibalize one or two for parts to make one of them
work. I also buy or download the manuals:
<http://802.11junk.com/jeffl/pics/home/slides/BL-shop5.html>
Notice that there are three HP8620C sweep generators, and three
SSI/Wavetek 3000b service monitors in the photo.

If the schematics once existed, they will eventually appear on
someones web pile. The sellers of manuals seem to be very good at
obtaining obscure manuals. I've posed schematics for some of the
stuff I've helped design on my web pile. Much more difficult are
schematics with voltages and waveforms. That used to be standard
practice until about the 1970's, but has lost favor probably because
it requires the schematics to be printed in color.

--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
 
"Cydrome Leader" <presence@MUNGEpanix.com> wrote in message
news:n4q6hr$2tt$1@reader1.panix.com...
I've stared at well written service manuals (these actually exist, but
tend to be old) that just made no sense until the next day, or after a
break. Not a fan of touching service manuals with diry hands either.

Where I worked we had a copy machine in the shop and I would usually copy
the important pages of the service manual to take with me. Usually had them
already copied in a book I kept so I could fine the important pages quick
and took a copy of that with me.

The electrical blue prints for much of the wiring and some equipment was on
a computer and we had a large plotter so could run off what we needed to
take with us.
Sometimes I would make notes on the copies and leave them in the electrical
cabinet, or just write inside the cabinet with a marking pen.
 
On 16 Dec 2015 03:21:01 GMT, Allodoxaphobia
<knock_yourself_out@example.net> wrote:

On Tue, 15 Dec 2015 17:47:13 -0800, Jeff Liebermann wrote:

However, it also helps to pay attention. Do you see a problem here?
http://802.11junk.com/jeffl/crud/GX520-bad-caps.jpg

Either the (out of focus) black capacitors are installed backwards
or the board is mis-labled with the "+" signs.
Jonesy

Yep, you got it. Electrolytic capacitors are identified by a wide
stripe on the negative end. To make it easy to hand insert
electrolytics, the PCB is usually silk screen with a wide white area
around the corresponding negative wire. Usually, except for this find
Dell motherboard, that marks the positive lead instead with a wide
white area. To their credit, they added "+" marks, which I missed.
Having replace plenty caps on boards where the negative terminal is
marked, I didn't think to look for the "+" sign, and so installed it
backwards. The computer actually ran for a day or so, before it
started acting funny and blew the tops open. I initially thought I
had a batch of bad caps, so I replaced them a 2nd time, inserting them
backwards again. I knew I was in trouble when the caps got rather
warm. In desperation, I posted the photo to this newsgroup and got an
instant response. Only then did I notice that the PCB silk screen
markings were backwards.

Like I said, it pays to pay attention when re-capping.



--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
 
On 12/15/2015 8:08 PM, Jeff Liebermann wrote:
On 16 Dec 2015 03:21:01 GMT, Allodoxaphobia
knock_yourself_out@example.net> wrote:

On Tue, 15 Dec 2015 17:47:13 -0800, Jeff Liebermann wrote:

However, it also helps to pay attention. Do you see a problem here?
http://802.11junk.com/jeffl/crud/GX520-bad-caps.jpg

Either the (out of focus) black capacitors are installed backwards
or the board is mis-labled with the "+" signs.
Jonesy

Yep, you got it. Electrolytic capacitors are identified by a wide
stripe on the negative end. To make it easy to hand insert
electrolytics, the PCB is usually silk screen with a wide white area
around the corresponding negative wire. Usually, except for this find
Dell motherboard, that marks the positive lead instead with a wide
white area. To their credit, they added "+" marks, which I missed.
Having replace plenty caps on boards where the negative terminal is
marked, I didn't think to look for the "+" sign, and so installed it
backwards. The computer actually ran for a day or so, before it
started acting funny and blew the tops open. I initially thought I
had a batch of bad caps, so I replaced them a 2nd time, inserting them
backwards again. I knew I was in trouble when the caps got rather
warm. In desperation, I posted the photo to this newsgroup and got an
instant response. Only then did I notice that the PCB silk screen
markings were backwards.

Like I said, it pays to pay attention when re-capping.

Oh...that was too obvious. Missed it!

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."
 
On 12/15/2015 6:43 PM, Jeff Liebermann wrote:
On Wed, 16 Dec 2015 03:27:36 +0100, Sjouke Burry
burrynulnulfour@ppllaanneett.nnll> wrote:

However, it also helps to pay attention. Do you see a problem here?
http://802.11junk.com/jeffl/crud/GX520-bad-caps.jpg

A blue one with a headache.

The "bad-caps" is in the URL, so that's rather obvious. However,
that's the result, not the problem. The cause is quite obvious once
you see it. I posted the picture previously and Phil Allison caught
the problem almost instantly. I didn't.

Do you mean where someone mixed 85C caps (that failed) with 105C caps,
that look OK?

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."
 
Jeff Liebermann wrote:
However, it also helps to pay attention. Do you see a problem here?
?http://802.11junk.com/jeffl/crud/GX520-bad-caps.jpg?

85C?
 
On Tue, 15 Dec 2015 17:47:13 -0800, Jeff Liebermann wrote:
However, it also helps to pay attention. Do you see a problem here?
http://802.11junk.com/jeffl/crud/GX520-bad-caps.jpg

Either the (out of focus) black capacitors are installed backwards
or the board is mis-labled with the "+" signs.

Jonesy
--
Marvin L Jones | Marvin | W3DHJ.net | linux
38.238N 104.547W | @ jonz.net | Jonesy | FreeBSD
* Killfiling google & XXXXbanter.com: jonz.net/ng.htm
 
On Tue, 15 Dec 2015 07:37:42 -0800, John Robertson <spam@flippers.com>
wrote:

I must confess we do replace almost all electrolytic caps that are more
than about 30 years old in our vintage game monitors and amplifiers
(video/pinball/jukebox) as this saves a tremendous amount of
troubleshooting time. It is true that perhaps 60% of the caps replaced
are fine, but the rest are marginal at best and make all sorts of errors
creep in that would take hours to find otherwise.

<http://802.11junk.com/jeffl/pics/repair/slides/bad-caps.html>
I also do pre-emptive replacements on caps. Worse, if I find a cap
that is bulging or fails an ESR test, I replace *ALL* the caps that
are the same brand and value. Also, if I find a string of parallel
caps, and one is bad, I automatically assume that all of them are
either bad, or will soon fail. That may seem extreme, but I spend
more time extracting and replacing motherboards boards than I do
fixing them. It's easier and cheaper to replace everything that is
suspicious, than to deal with returns, rework, complaining customers,
reputation issues, etc. If the customer returns with the same
problem, but from a different cap, I have to do the rework for free,
which wipes all my profit from the initial repair. Do it right and do
it all the first time.

However, it also helps to pay attention. Do you see a problem here?
<http://802.11junk.com/jeffl/crud/GX520-bad-caps.jpg>


--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
 
On Wed, 16 Dec 2015 03:27:36 +0100, Sjouke Burry
<burrynulnulfour@ppllaanneett.nnll> wrote:

However, it also helps to pay attention. Do you see a problem here?
http://802.11junk.com/jeffl/crud/GX520-bad-caps.jpg

A blue one with a headache.

The "bad-caps" is in the URL, so that's rather obvious. However,
that's the result, not the problem. The cause is quite obvious once
you see it. I posted the picture previously and Phil Allison caught
the problem almost instantly. I didn't.



--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
 
On 16.12.15 2:47, Jeff Liebermann wrote:
On Tue, 15 Dec 2015 07:37:42 -0800, John Robertson <spam@flippers.com
wrote:

I must confess we do replace almost all electrolytic caps that are more
than about 30 years old in our vintage game monitors and amplifiers
(video/pinball/jukebox) as this saves a tremendous amount of
troubleshooting time. It is true that perhaps 60% of the caps replaced
are fine, but the rest are marginal at best and make all sorts of errors
creep in that would take hours to find otherwise.

http://802.11junk.com/jeffl/pics/repair/slides/bad-caps.html
I also do pre-emptive replacements on caps. Worse, if I find a cap
that is bulging or fails an ESR test, I replace *ALL* the caps that
are the same brand and value. Also, if I find a string of parallel
caps, and one is bad, I automatically assume that all of them are
either bad, or will soon fail. That may seem extreme, but I spend
more time extracting and replacing motherboards boards than I do
fixing them. It's easier and cheaper to replace everything that is
suspicious, than to deal with returns, rework, complaining customers,
reputation issues, etc. If the customer returns with the same
problem, but from a different cap, I have to do the rework for free,
which wipes all my profit from the initial repair. Do it right and do
it all the first time.

However, it also helps to pay attention. Do you see a problem here?
http://802.11junk.com/jeffl/crud/GX520-bad-caps.jpg


A blue one with a headache.
 
>"Does it, though? I mean, you could save even more time by just >running all the caps through an ESR meter test and just replacing >those that fail. Given how fragile some of those old PCB traces can >be, I'd only want to replace the caps that really way out of spec. "

Not so much that, but the ones that matter. For example you could draw a graph of the dissipation of a vertical deflection IC (or transistors for that matter)against the ESR of the boost cap. Usually 100 - 330 uF in value these boost the Vcc to the ouptu stage during retrace. When the cap ESR rises the output circuit operates in linear mode longer to try and compensate. Usually, its dissipation is quite a bit higher before you see anything on the screen like a compression at the top or a foldover. It over heats and burns out and about 80 % of the time the tech finds it with a foldover after replacing the IC or transistors.

So there are CERTAIN ones you want to just replace or at least check. But things are out there with hundreds of caps and it might be impractical to change them all.

And another thing, I would highly recommend getting the unit working properly before recapping. Then, recap in steps, rechecking proper operation in between every one.

Maybe some people are lucky, but I have been where Murphy's law was strictly enforced. And Murphy himself told me "You make your own luck". (the story of Murphy is something I will post eventually but it belongs in another place)
 
In article <1aj17bp99gqdjcv4v5k0r6bkst0ldahl6l@4ax.com>,
Jeff Liebermann <jeffl@cruzio.com> wrote:

However, it also helps to pay attention. Do you see a problem here?
http://802.11junk.com/jeffl/crud/GX520-bad-caps.jpg

A blue one with a headache.

The "bad-caps" is in the URL, so that's rather obvious. However,
that's the result, not the problem. The cause is quite obvious once
you see it. I posted the picture previously and Phil Allison caught
the problem almost instantly. I didn't.

Are *all* *four* of those large caps installed backwards?!?

Yah. Amazing you didn't have a chassis full of oily linguine there.
 
Jeff Liebermann wrote:

On Tue, 15 Dec 2015 15:49:13 -0600, Jon Elson <jmelson@wustl.edu
wrote:

Jeff Liebermann wrote:

3. Things go better if you have a schematic, gallon of coffee, a
working unit to compare, and a parts unit to cannibalize.

Oh wow! This one is up there with Murphy's law!

And, unless you are the manufacturer of said device, much of the above
will never be available.

Gallons of coffee are available at your local supermarket.

I know where to find coffee, although I don't drink it.


I practice what I preach. If really want something to work, I buy 3
of them, and cannibalize one or two for parts to make one of them
work. I also buy or download the manuals:
http://802.11junk.com/jeffl/pics/home/slides/BL-shop5.html
Notice that there are three HP8620C sweep generators, and three
SSI/Wavetek 3000b service monitors in the photo.
Manuals for test gear are usually available. But, for a lot of consumer
gear, automotive modules and industrial gear, they may NOT be! That can be
a real headache.

Old CNC control gear used to have fabulous manuals, with a theory manual
three times as big as the schematics.

But, on later gear, you were lucky to get drawings of the cables, some
configuration charts, and that was ALL that was ever allowed outside the
factory. So, you had to reverse engineer how a lot of stuff worked to
figure out what was wrong with it.

A woking unit to compare to is REALLY a huge help, when available.

Jon
 
"Cursitor Doom" wrote in message news:n4miat$8a6$1@dont-email.me...

Anyone care to share their experience on the correct approach to
troubleshooting? I'll kick off by suggesting:

1. Assume nothing.


2. If at first you don't succeed, destroy any evidence that you even tried!


3. Try Percussive maintenance first. If it works after you bang it, it has
intermitant connections, or components.


Shaun
 

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