Golden Rules of Troubleshooting

[Shaun]

"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.


Check all user accessible parts and power components, like transistors and
Diodes.
After the visual check of the components for burnt parts or over heated
parts and a smell test; I would flip the board over and inspect all the
solder joints usually with a magnifying lens and and check for cold or
fractured solder joints. When I'd find one I usually remove the old solder
with a solder sucker or wick and then re-solder the joint making sure the
component lead gets lots of heat during the solder process and I use real
solder. Parts or the board around components that got hot often had bad
solder joints from heating and cooling.

Shaun - serious post.

 

[pfjw@aol.com]

Amen to that- the working unit to compare!

I finished the Dynaco ST120 from hell last night. It came to me "fuzzy in one channel". And it was.

First run-through: One output transistor in the 'good' channel, one output and one driver in the other, still fuzzy. I wound up ohming out every part, comparing to the good channel. Six drifted resistors later, I got to the 5..1V zener diode. Bingo. It had become a 94 ohm resistor.

Given that these beasts blow up by the numbers, I generally install sockets for the outputs, and do the TIP mod once ALL else is under control.

Peter Wieck
Melrose Park, PA

 

[pfjw@aol.com]

Ah, they ain't no how as bad as all that these days. Between the various mods, Factory and susequent, they have been rendered pretty bullet-proof, very stable, and as simple SS amps go, fairly melifluous. They were made in the uncounted tens of thousands, and uncounted thousands survive. With a few hours of simple work and not much cost, a decent 50+ watt amp may be had. As it happens, I keep two (full mods) that see very rough service, and have done so in one case for 2 years of 24/7 use in a desert climate, not conditioned. 100F+ from may to November. It now sits in my shop system seeing about 3 hours per week, these days.

Who would put a curtain over an amp capable of frying an egg in the first place?? That smacks of terminal idiocy.

Peter Wieck
Melrose Park, PA

 

[Jeff Liebermann]

On Wed, 16 Dec 2015 11:34:43 -0800, dplatt@coop.radagast.org (Dave
Platt) wrote:

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?!?

Yep. When I do something wrong, I'm consistent. As I previously
ranted, when I find one bad cap of a type and value, I replace *ALL*
the caps of the same type and value. My time is more expensive than
the extra caps.

>Yah. Amazing you didn't have a chassis full of oily linguine there.

Actually, the machine ran quite nicely for a day or two the first time
I put the caps in backwards. Eventually, it started acting strangely
so I retreived it from the customers. All 4 caps were bulging. So, I
replaced all 4 caps again, putting them in backwards again. That's
when I noticed that they were getting hot, which prompted my initial
Usenet posting. I too would have expected at least a small explosion,
but nothing happened.

--
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

 

[John Robertson]

On 12/17/2015 9:56 AM, Jeff Liebermann wrote:

On Wed, 16 Dec 2015 11:34:43 -0800, dplatt@coop.radagast.org (Dave
Platt) wrote:

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?!?

Yep. When I do something wrong, I'm consistent. As I previously
ranted, when I find one bad cap of a type and value, I replace *ALL*
the caps of the same type and value. My time is more expensive than
the extra caps.

Yah. Amazing you didn't have a chassis full of oily linguine there.

Actually, the machine ran quite nicely for a day or two the first time
I put the caps in backwards. Eventually, it started acting strangely
so I retreived it from the customers. All 4 caps were bulging. So, I
replaced all 4 caps again, putting them in backwards again. That's
when I noticed that they were getting hot, which prompted my initial
Usenet posting. I too would have expected at least a small explosion,
but nothing happened.

Nice that there were no explosions - I'm sure your customer would have
been nonplussed.

(ducking from the coffee explosion)

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."

 

[Ralph Mowery]

"Jeff Liebermann" <jeffl@cruzio.com> wrote in message
news:ndt57bhk8bil21l66rvfp34dj8r813lhoi@4ax.com...

Yep. When I do something wrong, I'm consistent. As I previously
ranted, when I find one bad cap of a type and value, I replace *ALL*
the caps of the same type and value. My time is more expensive than
the extra caps.

Yah. Amazing you didn't have a chassis full of oily linguine there.

Actually, the machine ran quite nicely for a day or two the first time
I put the caps in backwards. Eventually, it started acting strangely
so I retreived it from the customers. All 4 caps were bulging. So, I
replaced all 4 caps again, putting them in backwards again. That's
when I noticed that they were getting hot, which prompted my initial
Usenet posting. I too would have expected at least a small explosion,
but nothing happened.

Interisting it ran at all.

It is easy to get into a bad pattern of doing things. A coworker and I were
repairing some flouresence lights in the plant. Got to one and put in new
tubes and it did not come on. This did not phase us as we often will get a
bad tube or so as there are thousands in the plant we often will replace
over 100 tubes in a day. Sometimes we get bad tubes so put in another set
and still no light. Decided it was the ballast, so replaced that. Still no
light. Knew we had power as there were about 20 other lights in the room.
Replaced the ballast 2 more times and sitll no light. This ballast had been
replaced before as there were several places where the wires were spliced
together with wire nuts. One would thing with only 8 wires it would be easy
to get it going. Got time to go home. I went up the next day by myself
and decided to try one more time. This time I removed all the wires and
instead of just going by the color of the wires, actually trace the wiring
out. This time it lite just fine.

What we were doing wrong was just matching the wire colors and as it had
been replaced before the colors did not go to the same place.

 

[Cydrome Leader]

Ralph Mowery <rmowery28146@earthlink.net> wrote:

"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..

Give him credit for at least swapping out indicator bulbs.

 

[Cydrome Leader]

Ralph Mowery <rmowery28146@earthlink.net> wrote:

"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.

There always seems to come a point when people stop updating the stickers
inside the cabinet or the service books with all updates, past problems
and more importantly field modifications and why they were done. This
seems to happen around the time the safety switches start wear out and get
bypassed or panels and covers start to go missing.

 

[Chuck]

On Thu, 17 Dec 2015 05:22:59 -0800 (PST), "pfjw@aol.com"
<pfjw@aol.com> wrote:

Amen to that- the working unit to compare!

I finished the Dynaco ST120 from hell last night. It came to me "fuzzy in one channel". And it was.

First run-through: One output transistor in the 'good' channel, one output and one driver in the other, still fuzzy. I wound up ohming out every part, comparing to the good channel. Six drifted resistors later, I got to the 5.1V zener diode. Bingo. It had become a 94 ohm resistor.

Given that these beasts blow up by the numbers, I generally install sockets for the outputs, and do the TIP mod once ALL else is under control.

Peter Wieck
Melrose Park, PA
Peter,

Who in their right mind would still be using one of these? They were
considered to be an awful amps back in the 70s. One I saw burned down
a house. The carbon resistors caught fire and there happened to be a
curtain draped across the top of the amplifier. After seeing this
amp, I refused to work on them.

---
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus

 

[Jeff Liebermann]

On Wed, 16 Dec 2015 20:13:52 -0600, "Shaun" <stereobuff07@gmail.com>
wrote:

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

1. Assume nothing.

1a. Trust nobody (except your certificate authority).
1b. Believe no one.
1c. Presume nothing.
1d. Ignore fashionable explanations.
1e. Distrust authority.
1f. Ignore all advice.
1g. Test all new replacement components.

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

I never make the same mistake twice. Five or six times is my average.

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

Nope. Clean the device first. Depending on the type of filth, that
can be blowing off the dust with compressed air, or washing with a
household cleaner to remove fingerprints, dirt, crud, slime, food,
whatever. Cleaning allows you time to inspect the device, where you
might visually find the problem. Often, the problems go away with the
filth. Customers don't believe that anything has been repaired unless
it's clean.

Instead of beating on the box, try turning it upside down and shaking.
If you hear something rattle around, you've either found the problem,
or what's left of some component. Loose screws and spare parts on new
electronics are amazingly common.

--
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

 

[Jeff Liebermann]

On Tue, 15 Dec 2015 18:31:14 -0500, "Ralph Mowery"
<rmowery28146@earthlink.net> wrote:

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.

What? You don't like my method of documenting changes?
<http://members.cruzio.com/~jeffl/k6bj/K6BJ%20Repeater/slides/Documentation.html>
I think it's been like that since at least 2001.

Incidentally, I use a special ink for the purpose, that fades to
invisibility in about a year. It helps keep the manuals nice and
clean.

--
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

 

[John-Del]

On Friday, December 18, 2015 at 7:37:37 AM UTC-5, Mark Zacharias wrote:

Prefer direct-coupled amps (with a competent protection circuit!)
Mark Z.

Funny how certain things trigger a memory of something forgotten for years. I had a Hitachi brand receiver that the customer said blew out several speakers on one side. I checked the outputs, nothing shorted so I hooked up some cheap TV speakers at low volume and there was no DC to speak of on either side and it was clean and clear. I let it run a couple of hours and suddenly there was a loud hum, pop, and one TV speaker that puked it's voice coil. This was direct coupled amp with no type of speaker protection. Ended up junking it.

 

[Mark Zacharias]

<pfjw@aol.com> wrote in message
news:a117378b-ecb2-4aaf-be0f-c6bac46c07a6@googlegroups.com...

Ah, they ain't no how as bad as all that these days. Between the various
mods, Factory and >susequent, they have been rendered pretty bullet-proof,
very stable, and as simple SS amps >go, fairly melifluous. They were made
in the uncounted tens of thousands, and uncounted >thousands survive. With
a few hours of simple work and not much cost, a decent 50+ watt >amp may be
had. As it happens, I keep two (full mods) that see very rough service, and
have >done so in one case for 2 years of 24/7 use in a desert climate, not
conditioned. 100F+ from >may to November. It now sits in my shop system
seeing about 3 hours per week, these days.

Who would put a curtain over an amp capable of frying an egg in the first
place?? That >smacks of terminal idiocy.

Peter Wieck
Melrose Park, PA

Personally I wouldn't use an ST-120 simply because I find capacitor-coupled
amps to sound muddy, and yeah - I hated working on the things. Piece of crap
really.

Prefer direct-coupled amps (with a competent protection circuit!) although I
do like an autoformer coupled McIntosh...

Mark Z.

 

[Cydrome Leader]

Jeff Liebermann <jeffl@cruzio.com> wrote:

On Tue, 15 Dec 2015 18:31:14 -0500, "Ralph Mowery"
rmowery28146@earthlink.net> wrote:

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.

What? You don't like my method of documenting changes?
http://members.cruzio.com/~jeffl/k6bj/K6BJ%20Repeater/slides/Documentation.html
I think it's been like that since at least 2001.

ha. Love the metal can transistor diagram. At least these aren't drawn on
paper bags or cardboard and then thrown away.

Incidentally, I use a special ink for the purpose, that fades to
invisibility in about a year. It helps keep the manuals nice and
clean.

They should make heated pens for writing on thermal paper.

 

[Cydrome Leader]

Jeff Liebermann <jeffl@cruzio.com> wrote:

On Fri, 18 Dec 2015 20:31:53 +0000 (UTC), Cydrome Leader
presence@MUNGEpanix.com> wrote:

Jeff Liebermann <jeffl@cruzio.com> wrote:
On Tue, 15 Dec 2015 18:31:14 -0500, "Ralph Mowery"
rmowery28146@earthlink.net> wrote:

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.

What? You don't like my method of documenting changes?
http://members.cruzio.com/~jeffl/k6bj/K6BJ%20Repeater/slides/Documentation.html
I think it's been like that since at least 2001.

ha. Love the metal can transistor diagram. At least these aren't drawn on
paper bags or cardboard and then thrown away.

That scribbling wasn't one of mine. I usually draw an isometric
scribbling of the transistor or IC so that one can tell if it's a top
or bottom view. I think the red markings on the various drawings are
mine. Red is useful because it disappears when copied.

What the color of highlighter that would copy solid black even though you
could still read the original?

The copiers here are just color scanner/printers so they don't have the
same spectral sensitivity as the old machines so I can't test.

Incidentally, I use a special ink for the purpose, that fades to
invisibility in about a year. It helps keep the manuals nice and
clean.

They should make heated pens for writing on thermal paper.

Ummm... They do. It's called a soldering iron. However, there's a
trick to using a soldering iron for writing. Be sure to grab the
correct end of the soldering iron. The rest is self evident and easy.

Too hot and the thermal paper cycles back to white. It does weird things
when heated to the transition temp range.

 

Cursitor Doom <curd@notformail.com> wrote:

Anyone care to share their experience on the correct approach to
troubleshooting?

Maybe I've been hanging out around too many manager or business types,
but I'd suggest:

Find out if a working new (or used) example of the item in question
is available, and what it costs.

Under a certain amount, it won't pay to spend time fixing it, unless
there are some other circumstances involved. (It was grandma's radio,
or whatever.)

Between that amount and some other, really high amount, it might pay to
spend time fixing it.

Above that really high amount, they are either wanting confirmation that
it is broken, so they can persuade their boss to buy a new one, OR
hoping to blame you for an inability to fix it, so *you* have to buy the
new one.

Just because you're paranoid doesn't mean that they *aren't* out to get
you.

Matt Roberds

 

[Jeff Liebermann]

On Fri, 18 Dec 2015 20:31:53 +0000 (UTC), Cydrome Leader
<presence@MUNGEpanix.com> wrote:

Jeff Liebermann <jeffl@cruzio.com> wrote:
On Tue, 15 Dec 2015 18:31:14 -0500, "Ralph Mowery"
rmowery28146@earthlink.net> wrote:

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.

What? You don't like my method of documenting changes?
http://members.cruzio.com/~jeffl/k6bj/K6BJ%20Repeater/slides/Documentation.html
I think it's been like that since at least 2001.

ha. Love the metal can transistor diagram. At least these aren't drawn on
paper bags or cardboard and then thrown away.

That scribbling wasn't one of mine. I usually draw an isometric
scribbling of the transistor or IC so that one can tell if it's a top
or bottom view. I think the red markings on the various drawings are
mine. Red is useful because it disappears when copied.

Incidentally, I use a special ink for the purpose, that fades to
invisibility in about a year. It helps keep the manuals nice and
clean.

They should make heated pens for writing on thermal paper.

Ummm... They do. It's called a soldering iron. However, there's a
trick to using a soldering iron for writing. Be sure to grab the
correct end of the soldering iron. The rest is self evident and easy.

--
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

 

"OR
hoping to blame you for an inability to fix it, so *you* have to buy >the
new one. "

For that, they are going to need weapons. I mean like the government has.

 

[Jeff Liebermann]

On Fri, 18 Dec 2015 23:28:59 +0000 (UTC), Cydrome Leader
<presence@MUNGEpanix.com> wrote:

What the color of highlighter that would copy solid black even though you
could still read the original?

I don't know and too lazy to test it on my copier.

Interesting stuff:
<http://www.protectedpaper.com/category_s/17.htm>

The copiers here are just color scanner/printers so they don't have the
same spectral sensitivity as the old machines so I can't test.

I have an (old) Canon PC785 mono copier which should work. However, I
don't have any highlighters to try.

Incidentally, I use a special ink for the purpose, that fades to
invisibility in about a year. It helps keep the manuals nice and
clean.

They should make heated pens for writing on thermal paper.

Ummm... They do. It's called a soldering iron. However, there's a
trick to using a soldering iron for writing. Be sure to grab the
correct end of the soldering iron. The rest is self evident and easy.

Too hot and the thermal paper cycles back to white. It does weird things
when heated to the transition temp range.

Too hot and the paper catches fire. As I recall, the paper was black
or brown before it started burning. I just tried it with some thermal
receipt printer paper. It didn't go back to white.

--
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

 

[Ralph Mowery]

<mroberds@att.net> wrote in message news:n52ael$dqs$2@dont-email.me...

Cursitor Doom <curd@notformail.com> wrote:
Anyone care to share their experience on the correct approach to
troubleshooting?

Maybe I've been hanging out around too many manager or business types,
but I'd suggest:

Find out if a working new (or used) example of the item in question
is available, and what it costs.

Under a certain amount, it won't pay to spend time fixing it, unless
there are some other circumstances involved. (It was grandma's radio,
or whatever.)

That is the way I have looked at lots of things. The repair parts often
cost more than the origional item. At work there was a motor and gear box
of around 1/2 HP. To get a new motor or gear box actually cost within $ 5
of a whole new motor and gearbox. Then the company would have to pay the
mechanic over $ 40 an hour to rebuild the unit as they were always replaced
as a unit.