Consumer electronics "war stories"

[Chuck]

On Sun, 6 Dec 2015 17:23:59 -0800 (PST), Phil Allison
<pallison49@gmail.com> wrote:

Chuck wrote:




The light dimmer was putting an enormous amount of hash on the mains;
somehow it was getting into the microprocessor circuitry. I had seen
this before on much cheaper items so I had a hunch that this was the
problem.



** Wall dimmers put large voltage spikes on the wiring going to the lamp/s concerned - two spikes per cycle at up to the peak AC voltage. This radiates as buzzing noise across the audio and also AM radio bands.

Well shielded, low impedance gear is not affected but anything high impedance and not well shielded picks it up. Electric guitars and some keyboards are particularly susceptible.

Seems your Tandberg was too and that is piss poor design.


.... Phil

Phil,
Did you ever see the Tandberg cd player (1987) that cost over $1000.00
U.S. that had a plastic Philips chassis that never functioned
correctly even when new? I was upset when I bought a Philips with the
same chassis for $125.00 and had to return it. Imagine the flack we
got when selling this turd.

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[Jon Elson]

Mike Tomlinson wrote:

En el artĂ­culo <vtm66b5hsssqq9u6s1fde1vo8t87vve09b@4ax.com>, Jeff
Liebermann <jeffl@cruzio.com> escribiĂł:

http://members.cruzio.com/~jeffl/nooze/support.txt

Good fun. Thanks for posting that.

Number 10 reminded me of this:

https://en.wikipedia.org/wiki/Lp0_on_fire

Ah, we had a couple of those. We had a fairly large 360 system at
Washington University. 1401 and 7094, then 360/50 and then 360/65.

One of the routines that made one think of CIA dead drops in the middle of
the night was the routine for printing paychecks. (I guess vendor checks
were similar, too.) They had the box of continuous form checks locked in a
bank vault in the basement of the administration building. The box was
taped shut with signatures across the seal. When they opened the box, two
people had to be present and they had to sign a log sheet with the serial
number of the top check. They carried the box to the computer center,
loaded it into the printer and the program printed a sample form with VOID--
VOID--VOID all across it, but other info in the right place so they could
align the forms. When all was OK, they told the program to print the
checks. Then, they had to fill out and sign the log sheet reporting which
forms serial # were used in the aligning process and the first and last
forms serial # of the printed check run. Then the whole process was
reversed to get the box sealed and locked into the vault. During the whole
process, nobody was ever supposed to leave the side of the printer.

Well, imagine the confusion when in the middle of the print run the printer
started sparking and set the continuous forms checks on fire! I heard about
this 2nd hand, but apparently the accounting guys were running around like
decapitated chickens! They didn't even know how to properly log what had
happened.

I'm pretty sure we had another paper on fire event, but it was just standard
print output that time.

Jon

 

[Cydrome Leader]

Chuck <ch@dejanews.net> wrote:

On Mon, 7 Dec 2015 17:21:35 +0000 (UTC), Cydrome Leader
presence@MUNGEpanix.com> wrote:

Chuck <ch@dejanews.net> wrote:
On Thu, 3 Dec 2015 06:34:55 -0600, "Mark Zacharias"
mark_zacharias@sbcglobal.net> wrote:

OK, so it appears there is very little to discuss on this group in areas
like repairing audio components, amps, receivers, power supplies, etc these
days.

I "tune in" here almost daily and rarely find anything of interest to me.

Maybe we could share some "war stories" of cool repairs we have done in the
past.

Re-live some past glories?

The first time you traced down a bad reset line for a microprocessor?

That integrated amp that blew a channel about once a year until you caught
that bias diode occasionally opening up?

Sansui 5000A's? (yuck)

Crappy Euro caps in Tandberg tape decks?

Those times you sweated whether you could even get this thing put back
together?

Any more recent successs stories to brag about?

C'mon, don't we all enjoy patting ourselves on the back, really?


Mark Z.
The receiver tech was flummoxed by one of those large 1970s Pioneer
receivers. It had a problem none of us had seen before and we were a
high volume audio chain. There was slight audio distortion on both
channels, only on FM. We all worked commission only so I was the only
one to volunteer to help him out. To cut to the chase, the receiver
had an over designed mute circuit that was 3 or 4 stages deep, At the
deepest stage there was one of the Sanyo electrolytics that became a
common failure item many years later which was slightly leaky.

I've got another one. In the early 80s there were these 19" Hitachi
tvs that ghosted. It looked exactly like a bad delay line. By that
time I ran the TV service department for the same company. We had
just switched over to the big box store concept and I was inundated
with broken tvs. Out of desperation, I switched out the CRT and the
ghosting disappeared. We sold 1000s of these sets and I saw the
problem 3 more times.

And another. Kenwood sold these Funai made cd changers that never
worked properly. All of them would come back with skipping or not
playing discs problems. Kenwood came out with 3 or 4 mods, none which
worked. Sometimes they would work for months before they came back.
Somehow I found out if the mechanism retaining springs were stretched
so the mechanism didn't sag at all, the problem disappeared. Called
up Kenwood and they put out a mod kit that included strong springs
which also didn't allow any downward movement of the mechanism.

Was that the type with the CD cartridge, like a trunked automotive unit?
Those things were all such garbage.
No. It was a 5 disc carousel. Kenwood didn't have a design in the
pipeline so they outsourced it.

Sort of sad somebody messed up a carousel. The cartridge based changers
were infuriating.

Anything that requires extensive soldering and screwing around with that
medical type tape to open up, like portable tape/CD players and now
cameras suck too.

 

[Chuck]

On Mon, 7 Dec 2015 17:21:35 +0000 (UTC), Cydrome Leader
<presence@MUNGEpanix.com> wrote:

Chuck <ch@dejanews.net> wrote:
On Thu, 3 Dec 2015 06:34:55 -0600, "Mark Zacharias"
mark_zacharias@sbcglobal.net> wrote:

OK, so it appears there is very little to discuss on this group in areas
like repairing audio components, amps, receivers, power supplies, etc these
days.

I "tune in" here almost daily and rarely find anything of interest to me.

Maybe we could share some "war stories" of cool repairs we have done in the
past.

Re-live some past glories?

The first time you traced down a bad reset line for a microprocessor?

That integrated amp that blew a channel about once a year until you caught
that bias diode occasionally opening up?

Sansui 5000A's? (yuck)

Crappy Euro caps in Tandberg tape decks?

Those times you sweated whether you could even get this thing put back
together?

Any more recent successs stories to brag about?

C'mon, don't we all enjoy patting ourselves on the back, really?


Mark Z.
The receiver tech was flummoxed by one of those large 1970s Pioneer
receivers. It had a problem none of us had seen before and we were a
high volume audio chain. There was slight audio distortion on both
channels, only on FM. We all worked commission only so I was the only
one to volunteer to help him out. To cut to the chase, the receiver
had an over designed mute circuit that was 3 or 4 stages deep, At the
deepest stage there was one of the Sanyo electrolytics that became a
common failure item many years later which was slightly leaky.

I've got another one. In the early 80s there were these 19" Hitachi
tvs that ghosted. It looked exactly like a bad delay line. By that
time I ran the TV service department for the same company. We had
just switched over to the big box store concept and I was inundated
with broken tvs. Out of desperation, I switched out the CRT and the
ghosting disappeared. We sold 1000s of these sets and I saw the
problem 3 more times.

And another. Kenwood sold these Funai made cd changers that never
worked properly. All of them would come back with skipping or not
playing discs problems. Kenwood came out with 3 or 4 mods, none which
worked. Sometimes they would work for months before they came back.
Somehow I found out if the mechanism retaining springs were stretched
so the mechanism didn't sag at all, the problem disappeared. Called
up Kenwood and they put out a mod kit that included strong springs
which also didn't allow any downward movement of the mechanism.

Was that the type with the CD cartridge, like a trunked automotive unit?
Those things were all such garbage.

No. It was a 5 disc carousel. Kenwood didn't have a design in the
pipeline so they outsourced it.

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On Saturday, December 5, 2015 at 4:30:21 PM UTC-5, Chuck wrote:

On Fri, 4 Dec 2015 07:13:43 -0800 (PST), makolber@yahoo.com wrote:

One of my favorite stories is from electronics lab in college.

We had to build a small two stage transistor audio amp in the lab with parts from the stock room, onto a protoboard like breadboard.

My lab partners and I were experienced hams and got ours working in no time , no problems.

The PHD proffesor called me over to help him troubleshoot another groups that they could not get to work.

The design had a 10uf cap between the two stages.

I looked at the other groups breadboard and immediatly saw a tiny ceramic cap with a 10 printed on it between the two stages.

I pointed to the cap and said, that doesn't look right.

Got an A in that lab.

========================
Oh another one.

I worked for a company that made CATV settop boxes.
I wandered into the lab where a group of young engineers were stuck troubleshooting a new box design. The picture was black and white and they could not figure out why there was no color. Looking into the box I saw a crystal marked 3.579545.

On a total whim, I put my fingers on the crystal.

The picture immediatly snapped into color!!!!

I was amazed myself but didn't let it show....I just cooly said, there is your problem and walked away.



And lastly, in the same vein
you will all enjoy this story

http://www.rfcafe.com/references/popular-electronics/me-technician-you-engineer-february-1963-popular-electronics.htm

Have fun

Mark







Mark...
===================






For a very short time in the 1980s, Kenwood manufactured
amplifiers with wrong value resistors at various locations. The
first one was a bear because I had never seen a Japanese company
make that kind of mistake.

Lawsuits over the years have shown their companies to be just as liable occasionally, too (like with Nomura, Sumitomo, Mitsubishi, Toyota, Honda, Mazda, Hitachi and others...) I think that things are done less purposely with regards to American markets, though.

 

[Ralph Mowery]

<mogulah@hotmail.com> wrote in message
news:0d1e8a73-0190-4762-8391-6d19e0320d2d@googlegroups.com...
On Saturday, December 5, 2015 at 4:30:21 PM UTC-5, Chuck wrote:

On Fri, 4 Dec 2015 07:13:43 -0800 (PST), makolber@yahoo.com wrote:

One of my favorite stories is from electronics lab in college.

We had to build a small two stage transistor audio amp in the lab with
parts from the stock room, onto a protoboard like breadboard.

My lab partners and I were experienced hams and got ours working in no
time , no problems.

At college I had a lab with the same thing. We designed simple circuits and
built them and took measurments on them. There were boxes of parts that
were suspose to be the same parts. Some of the parts were either bad or out
of spec. Not on purpose, they just got that way over the years. Me and a
person I was with usually could locate the bad parts and get our project
going first. Got to be a joke that the ones that got theirs to work had the
lucky box with all good parts for that design.

 

Mark Zacharias <mark_zacharias@sbcglobal.net> wrote:

Maybe we could share some "war stories" of cool repairs we have done
in the past.

It's definitely not consumer electronics, but here goes.

I used to work at a company that made flight simulators. My official
job was writing code to make the navigation instruments display
correctly, according to the simulated position of the aircraft, which
frequencies the radios were tuned to, the position of circuit breakers,
etc.

Some of the laws of nature at that particular job included:

1) Techs string wire.

2) Programmers write programs.

3) Techs never make mistakes when stringing wires.

4) No programmer could ever possibly understand the intricacies of
stringing wires. Therefore, any complaints by programmers about the
wiring can usually be disregarded.

5) Any persistent complaints about the wiring can be remedied by telling
the programmers to work around it in the code.

Never being one to obey the laws of nature, I brought in my own meter
and checked things out when the sim didn't seem to work right. My boss
knew that I had something of a clue; I had been giving "how to read a
schematic" lessons to a few of my cow-orkers (in software) who were also
new hires or just wanted to know how. He basically told me that he
didn't mind me doing my own checks as long as I was careful with the sim
hardware, and that I should expect the techs to get mad at me if they
ever saw me doing it.

I couldn't get the right DME indicator to light up in one sim. (It was
a box in the instrument panel with three 7-segment displays and a couple
of buttons. It was supposed to display how far the airplane was from a
particular radio station.) After a few rudimentary checks of my code, I
wrote up a "right DME inop" trouble ticket. The technician wrote back,
"Wiring checks to print, DME sent for repair". Sure enough, there was a
hole in the panel. When it was again filled, I tried again...no joy. I
swapped the left and right indicators - hmm, the problem stayed with the
socket instead of following the indicator. I broke out the wiring
diagram and my own personal multimeter and started chasing around behind
the panel - no wires or pins for power on the right DME socket. (It was
something like a DB25 or DB37, with individual "crimp and poke"
contacts.) I dutifully re-opened the ticket, and the tech dutifully
wrote "wiring checks to print" and closed it again.

About this time, the sim was shipped to the site, even though it was
broken. The standard process was to completely build the sim at the
factory, test it out, ship it to the site, certify it, and put it in
revenue service. For sites that were far away from the factory, this
practice was generally followed, because it was expensive to ship people
to site to finish working on the sim. However, the site that was
closest to the factory (~3 hr drive) was notorious for the following:

Factory: We will have the sim done on $DATE.

Site: No no no! We've already sold time on that sim to customers on
$DATE-30days and we can't reschedule! We *must* have it here
sooner!

Factory: Why did you do that? The sim will not be done on
$DATE-30days. It will be broken and unusable for training.

Site: We don't care.

Factory: If we ship it at that time, it will suck.

Site: We don't care!!! Ship it shipit SHIPIT!!1!

Factory: <sigh> OK.

(time passes)
Site: Well you got the sim to us on time but it sucks! Everything's
broken and we can't put the customers on it! Fix it fixit
FIXIT!!1!

Factory: <sighs deeply, starts phoning rental car agencies and hotels>

So I get to the site and the site manager is bugging me about the right
DME indicator. I walk in to the site maintenance shop and tell the
techs there I need some connector pins, the crimper tool, some wire, and
a bench power supply. They are extremely wary of this as they have
experienced "programmers with screwdrivers" before, but they give me the
requested items and follow me into the sim, probably in hopes that my
body will shake and jerk in interesting ways as I electrocute myself.
I put the pins on the wires and put them in the (still vacant) slots on
the right DME connector. Wires run out under the panel to the power
supply, which temporarily gets the co-pilot's seat. Fire up the sim,
hit the power supply, and whaddayaknow - DME love for all. I
disappointed the techs, but the site manager was very happy.

I pointed out the relevant page in the wiring diagram book, so the site
techs could get it wired in correctly. I figured they had a lot more
experience than I did in fixing factory screwups. They were satisfied
with this, and I got to go home.

Matt Roberds

 

[Mike Tomlinson]

En el artículo <n4dume$d8b$1@dont-email.me>, mroberds@att.net escribió:

Factory: We will have the sim done on $DATE.

Site: No no no! We've already sold time on that sim to customers on
$DATE-30days and we can't reschedule! We *must* have it here
sooner!

Factory: Why did you do that? The sim will not be done on
$DATE-30days. It will be broken and unusable for training.

Site: We don't care.

Factory: If we ship it at that time, it will suck.

Site: We don't care!!! Ship it shipit SHIPIT!!1!

Factory: <sigh> OK.

(time passes)
Site: Well you got the sim to us on time but it sucks! Everything's
broken and we can't put the customers on it! Fix it fixit
FIXIT!!1!

Why does that sound so horribly, horribly familiar?

Brrr. Memories I'd rather forget.

--
(\_/) Tyson Fury: #homophobe #bigot #throwback #missinglink
(='.'=) #neanderthal #misogynist #redneck #dickhead
(")_(")

 

[Mark Zacharias]

<mroberds@att.net> wrote in message news:n4dume$d8b$1@dont-email.me...

Mark Zacharias <mark_zacharias@sbcglobal.net> wrote:
Maybe we could share some "war stories" of cool repairs we have done
in the past.

It's definitely not consumer electronics, but here goes.

I used to work at a company that made flight simulators. My official
job was writing code to make the navigation instruments display
correctly, according to the simulated position of the aircraft, which
frequencies the radios were tuned to, the position of circuit breakers,
etc.

Some of the laws of nature at that particular job included:

1) Techs string wire.

2) Programmers write programs.

3) Techs never make mistakes when stringing wires.

4) No programmer could ever possibly understand the intricacies of
stringing wires. Therefore, any complaints by programmers about the
wiring can usually be disregarded.

5) Any persistent complaints about the wiring can be remedied by telling
the programmers to work around it in the code.

Never being one to obey the laws of nature, I brought in my own meter
and checked things out when the sim didn't seem to work right. My boss
knew that I had something of a clue; I had been giving "how to read a
schematic" lessons to a few of my cow-orkers (in software) who were also
new hires or just wanted to know how. He basically told me that he
didn't mind me doing my own checks as long as I was careful with the sim
hardware, and that I should expect the techs to get mad at me if they
ever saw me doing it.

I couldn't get the right DME indicator to light up in one sim. (It was
a box in the instrument panel with three 7-segment displays and a couple
of buttons. It was supposed to display how far the airplane was from a
particular radio station.) After a few rudimentary checks of my code, I
wrote up a "right DME inop" trouble ticket. The technician wrote back,
"Wiring checks to print, DME sent for repair". Sure enough, there was a
hole in the panel. When it was again filled, I tried again...no joy. I
swapped the left and right indicators - hmm, the problem stayed with the
socket instead of following the indicator. I broke out the wiring
diagram and my own personal multimeter and started chasing around behind
the panel - no wires or pins for power on the right DME socket. (It was
something like a DB25 or DB37, with individual "crimp and poke"
contacts.) I dutifully re-opened the ticket, and the tech dutifully
wrote "wiring checks to print" and closed it again.

About this time, the sim was shipped to the site, even though it was
broken. The standard process was to completely build the sim at the
factory, test it out, ship it to the site, certify it, and put it in
revenue service. For sites that were far away from the factory, this
practice was generally followed, because it was expensive to ship people
to site to finish working on the sim. However, the site that was
closest to the factory (~3 hr drive) was notorious for the following:

Factory: We will have the sim done on $DATE.

Site: No no no! We've already sold time on that sim to customers on
$DATE-30days and we can't reschedule! We *must* have it here
sooner!

Factory: Why did you do that? The sim will not be done on
$DATE-30days. It will be broken and unusable for training.

Site: We don't care.

Factory: If we ship it at that time, it will suck.

Site: We don't care!!! Ship it shipit SHIPIT!!1!

Factory: <sigh> OK.

(time passes)
Site: Well you got the sim to us on time but it sucks! Everything's
broken and we can't put the customers on it! Fix it fixit
FIXIT!!1!

Factory: <sighs deeply, starts phoning rental car agencies and hotels

So I get to the site and the site manager is bugging me about the right
DME indicator. I walk in to the site maintenance shop and tell the
techs there I need some connector pins, the crimper tool, some wire, and
a bench power supply. They are extremely wary of this as they have
experienced "programmers with screwdrivers" before, but they give me the
requested items and follow me into the sim, probably in hopes that my
body will shake and jerk in interesting ways as I electrocute myself.
I put the pins on the wires and put them in the (still vacant) slots on
the right DME connector. Wires run out under the panel to the power
supply, which temporarily gets the co-pilot's seat. Fire up the sim,
hit the power supply, and whaddayaknow - DME love for all. I
disappointed the techs, but the site manager was very happy.

I pointed out the relevant page in the wiring diagram book, so the site
techs could get it wired in correctly. I figured they had a lot more
experience than I did in fixing factory screwups. They were satisfied
with this, and I got to go home.

Matt Roberds

Wow. Lots of times I'm too lazy to read to the end - but this was great!
Loved it!

mz

 

[Mark Zacharias]

How about another slant on "War Stories" ?

The least competent, most alcoholic, etc tech person you ever had to work
with or follow after they got fired?

When I was first starting in consumer electronics repair, (my first job in
the business, actually) I was hired to replace "Karl". He had a resume - in
the '70s a well respected shop paid for him to come over from Germany.

By my time however - apparently a broken down alcoholic.

He would "repair" tons of stuff, bill out huge amounts (paid on commision)
then abscond when the re-do's became too much.

I was charged with fixing his re-do's and generally cleaning up the chaos he
had left behind.

Next job - another shop. They had just fired the SAME GUY. Same situation.
Re-do's coming in one after another. Angry customers. Piles of screws and
small hardware in a pile on one corner of the bench. Dis-assembled units all
over the place, and I mean ALL OVER. A Teac A-4010 in about four different
parts of the shop. No pressure... I'd never even seen one before.

Next job - SAME DEAL. By now I was getting pretty good at
reverse-engineering other peoples screw-ups, but - really?

A couple examples:

Auto-reverse car cassette deck. He didn't have the correct drive belt, so he
had SUPER-GLUED the ends of the old belt together. Played about 2 mnutes, if
that.

A Marantz 1060 integrated amp (re-do) with a blown channel. He had substuted
a driver transistors with a similar package item. Unfortunately, the part he
used was a VOLTAGE REGULATOR IC and not even a transistor.

He had his "groupies" though. Some customers followed him from one job to
the next.

About 1987 Bang & Olufsen in Chicago contacted our shop for a reference on
this guy.

We were rolling on the floor!

Gave him an absolutely GLOWING reference. We could think of nothing funnier
than the prospect of this guy working for B&O.

(no he didn't get hired)


Good times.

 

"I was charged with fixing his re-do's and generally cleaning up the >chaos he
had left behind. "

Steve's TV, I doubt they are still around. Quit, went back a couple of times. One time they needed bo TV techs but needed an audio tech. Figured, hell I'll give audio a whirl. Not that I hadn't done any, just not exclusively.

Well there is this whole big stack of recalls (or redos) from the last guy. The Delco 2000 series car stereos. The guy's bench setup had a common ground for the speakers and he blew the audio output chip out of EVEY ONE OF THEM.

These are true four channels radios but not quad. these are not some elcheapo LAXXXX six buck chip. They were DM-165 mostly and they were over twenty bucks each, and he blew BOTH of them in each radio.

That was one of my last commission jobs. I made money. And after that SNAFU was cleared up the boss(es) standing around said "We're finally making money on audio". That part was a bit hellish. Back then we didn't even have a Hakko and those Delcos were among the first things that (regularly) came in that two sided boards with plated through holes.

Every last one of them. With the type B tape decks in them the belt would break and it would not eject, so no radio either. So many customers decided to pry the tape out, breaking the cassette guides. The belt is a buck, a set of these plastic pieces it twenty. Even though they were assholes who cost themselves some money there, they did happen to notice when the front speakers didn't work anymore after they got it back.

And then they bring it back and because of the common ground the bench speakers would play the L-R like the back channels of a quasi quad unit and when you turn the balance to one side it would sound almost normal. "Nothing wrong with it". Yeah right.

You can't really work techs on commission anymore. Back then, so many repairs involved simple parts that it could work with a guy who is good. There were shops though that I would not. If I do not see a good parts department fuck that. I ain't coming in and diagnosing all this only to wait weeks to complete the job to get paid. What's more, forget the free estimate, I ain't doing it.

When the shop[ makes money, the tech makes money on commission. One place I did work commission worked out pretty well. I was running though some of my old shit and part time, one week I made $480 in 12 hours. One week I worked about 30 hours and took home $775. And that was in the 1980s. Later, that job converted to hourly, at a quite good rate. It was slightly less money but it was steady. I liked the money steady and they liked the fact that I could no longer refuse jobs.

And that paid off for them.

Actually, now this is a LONG time ago and at $23 an hour, they threw me a set I had already been stumped on before. they said it is a do or die. It may have been a contract job, and when you cannot fix a contract job that is very bad. You can't just refund the money, you have to buy them another TV.

This was an RCA CTC 169. (I should have put thios in my other post but did not recall it then) Intermittently it would start up with the OSD shifted and no sound. Now this was a normal symptom for this chassis and I do not recall what the fix was, but in this case where the OSD is usually shifted to the right, this one was shifted to the left. (or vice versa but you get the idea, the other way)

it would never do it with the chassis flipped up. About ten people resoldered almost every joint on the board to no avail.

RINALLY I got it. It was a weak 503 KHz crystal at the jungle IC. the hell you say ? Well when the micro tells the set to come on it expects a source to come up right away which is scan derived. this feeds the EPROM which then reads its contents into RAM with the specific setup info and settings.

I started noticing that when this happened, the HV did not come up immediately. What it was is the crystal was weak or whatever and the oscillator took too much time to start. The micro is only sensitive to that data for a limited time and the window was closed by the time the EPROM spoke up. That chassis had a system that is operable without an EPROM. When it is in that mode it uses a set of parameters that do not match the hardware installed. Actually I do not recall ever seeing a CTC169 without an EPROM, but other models did. Some of them would autoprogram first time they were turned on after being unplugged. Those were the elcheapo models, but of other chassis'. I guess they used the same micros or at least similar code in them though.

So we got :

No sound - 503 KHZ crystal for horizontal osc.
No sound - vertical shaping IC.
Loses blue and green after CRT replacement - adjust vertical height.

I'd like to see some weirder ones than that.

 

[whit3rd]

On Thursday, December 10, 2015 at 1:00:55 PM UTC-8, Ralph Mowery wrote:

mogulah@hotmail.com> wrote in message

At college I had a lab ... There were boxes of parts that
were suspose to be the same parts. Some of the parts were either bad or out
of spec. Not on purpose, they just got that way over the years. Me and a
person I was with usually could locate the bad parts and get our project
going first. Got to be a joke that the ones that got theirs to work had the
lucky box with all good parts for that design.

I was teaching one such lab, with bar magnet/coil experiments, and had
an inspiration. I got some iron filings and sheets of paper, and
had the students lay the paper over their bar magnet and sprinkle
the filings over it.

There were a dozen bar magnets in the 'materials' box, and half of 'em had odd
fields. One had five identifiable poles. Using only the dipole-type
bar magnets, the class got better compliance than usual with the
expected behavior of poles and coils in motion.

 

[Chuck]

On Fri, 11 Dec 2015 06:02:13 -0600, "Mark Zacharias"
<mark_zacharias@sbcglobal.net> wrote:

How about another slant on "War Stories" ?

The least competent, most alcoholic, etc tech person you ever had to work
with or follow after they got fired?

When I was first starting in consumer electronics repair, (my first job in
the business, actually) I was hired to replace "Karl". He had a resume - in
the '70s a well respected shop paid for him to come over from Germany.

By my time however - apparently a broken down alcoholic.

He would "repair" tons of stuff, bill out huge amounts (paid on commision)
then abscond when the re-do's became too much.

I was charged with fixing his re-do's and generally cleaning up the chaos he
had left behind.

Next job - another shop. They had just fired the SAME GUY. Same situation.
Re-do's coming in one after another. Angry customers. Piles of screws and
small hardware in a pile on one corner of the bench. Dis-assembled units all
over the place, and I mean ALL OVER. A Teac A-4010 in about four different
parts of the shop. No pressure... I'd never even seen one before.

Next job - SAME DEAL. By now I was getting pretty good at
reverse-engineering other peoples screw-ups, but - really?

A couple examples:

Auto-reverse car cassette deck. He didn't have the correct drive belt, so he
had SUPER-GLUED the ends of the old belt together. Played about 2 mnutes, if
that.

A Marantz 1060 integrated amp (re-do) with a blown channel. He had substuted
a driver transistors with a similar package item. Unfortunately, the part he
used was a VOLTAGE REGULATOR IC and not even a transistor.

He had his "groupies" though. Some customers followed him from one job to
the next.

About 1987 Bang & Olufsen in Chicago contacted our shop for a reference on
this guy.

We were rolling on the floor!

Gave him an absolutely GLOWING reference. We could think of nothing funnier
than the prospect of this guy working for B&O.

(no he didn't get hired)


Good times.
Mark,

In the early 70s there was a company that sold strips of rubber of
various sizes with a razor blade, jig and a tube of super glue that
was supposed to be used to make belts for consumer electronics
equipment. I had never seen super glue before so I tried it. Once.

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

 

[Jeff Liebermann]

>Any more recent successs stories to brag about?

If you enjoy reading such stories, there are quite a few in the "Made
by Monkeys" section of various trade magazines. These highlight
quality control and design failures:
<http://www.electronicsweekly.com/made-by-monkeys/>
<http://www.designnews.com/archives.asp?section_id=1367>
If you're planning on designing the next big thing in consumer
products, or are wondering why some things just can't be repaired,
these columns (blogs) should be mandatory reading.


--
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 Fri, 11 Dec 2015 10:46:52 -0600, Chuck <chuck@mydeja.net> wrote:

In the early 70s there was a company that sold strips of rubber of
various sizes with a razor blade, jig and a tube of super glue that
was supposed to be used to make belts for consumer electronics
equipment. I had never seen super glue before so I tried it. Once.

Those are still sold and work reasonably well:
<https://www.google.com/#q=o-ring+splice+kit>

The trick is to cut the o-ring or whatever at an angle. That does
three things:
- It increases the surface contact area so that the glue has a better
grip.
- It converts some of the stresses from tension to shear, where
cyanoacrylate adhesives are stronger.
- When used as a compression seal, crushing the glue joint does NOT
crack the rather brittle glue joint.

The only gotcha I've run into is dealing with tight turns such as very
small diameter drive pulleys. Cutting the o-ring at a large angle
causes the glue joint to be longer. Too long, and it will crack if
wrapped around a small pully. Just size the angle for covering no
more than about 60 degrees around the pully, and I think it should be
ok.

Note: Super glue doesn't work if there's little contact area, so
splicing thin and flat belts doesn't work. I've had some luck using
contact cement with these, but not reliably.

--
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

 

[Adrian Tuddenham]

Mark Zacharias <mark_zacharias@sbcglobal.net> wrote:

Maybe we could share some "war stories" of cool repairs we have done in the
past.

I was called in unofficially to have a look at an X-ray machine in a
university crystallography lab, there was an intermittent fault which
shut it down after a few seconds of operation. The running time was
getting shorter and shorter and the manufacturers had given up on
finding the fault.

On the way there, I mentally ran through what I could remember about
X-ray machines (apart from the obvious dangers) and realised that most
of what I knew had come from reading my father's hand-written course
notes in the 1950s; they dated from when he was trained as an army
radiographerat the outbreak of WWII. I knew what an X-ray tube looked
like as a symbol, but what did one look like in reality?

On being introduced to the faulty machine, I glanced around the room and
saw a number of copper-and-glass objects on a shelf - and concluded that
they must be spare tubes. Luckily, the manufacturers had furnished a
full set of circuit diagrams and the lab had managed not to loose them,
so I knew what I was dealing with, even if I didn't initially know how
most of it worked. The circuits were all discrete components with
intermixed transistor, diode and relay logic.

By the end of the first day, I had gained a fair idea of how the power
supplies and safety circuits worked and had been instructed in the
necessary safety drill by the technician, so I was able to fire the
machine up and watch what happened. The fault showed up, but it all
happened so quickly that I wan't able to spot what was going on.

Luckily, on the morning of the second day, I happened to spot the tube
current meter flicker downwards and the voltmeter kick upwards just as
the fault occurred. Careful monitoring of the primary of the mains
transformer showed unstable mains voltage, which the control loop had
been over-compensating and then tripping out on over-voltage.

The cause was a burnt contact in the main contactor, so I stripped it
down and sandpapered the contacts, much to the amusement of the staff.

Fault cured - machine saved from the scrapheap.


--
~ Adrian Tuddenham ~
(Remove the ".invalid"s and add ".co.uk" to reply)
www.poppyrecords.co.uk

 

Been there done that. Good site. The name seems to imply it is a comedy site but it is not. I hope people are not too disappointed.

 

[Jeroni Paul]

jurb...@gmail.com wrote:

Well I guess it is my turn.

NAP bigscreen no sound - vertical control IC.

Everything runs off the data and clock lines. This IC does the "S" correction and things like that pertaining to linearity. It is of course bus addressed. The one line, data or clock, doesn't matter, was clamping the signal down to like 2 volts. Leaky. That meant the data from the EPROM was not read when the unit got initialized so it did not know which sound system it had and never upped that.

I had a similar fault in an Universum CRT TV set. It came with an all white screen sympthom that I traced to the RGB decoder matrix IC holding its RGB outputs to 0V. Replaced the IC, no joy. It was I2C controlled and I even built a simple interface to send commands from the PC, it seemed to ACK fine and all looked right. If not initialized at turn on the raster remained black but as soon as the outputs were activated in any way it would go full white.
Finally found the problem: it received a sandcastle signal from the sync processor IC that had the top pulses too low so the RGB IC was not locking on them. The picture improvement IC also connected to this signal had a leaky input and was eating half the signal.

 

[Jeroni Paul]

Chuck wrote:

In a similar vein to your remote story, we sold an $1800 Tandberg
cassette deck that came to the shop over and over again for not
responding to the transport keys. In the shop it always worked
perfectly. I decided to go to the customer's house after work to see
what the problem was. At his house, the keys didn't work. I spotted
a light dimmer on the wall. Turning it off and the deck worked
perfectly.

I have a SABA music system (radio + cassette + turntable + audio in/out plugs + remote control), time ago I had it connected to a desktop PC to play music from the PC. One day the printer attached to the same PC was taken out for repair due to clogged heads.

The next day I found the SABA turned on with the MUTE activated (the radio was selected so the FM display etc was all lit, but no sound). Since I never used to use the MUTE button and I was the only one at home to use that thing I was quite surprised. I unmuted it and turned it off, all appeared to work correctly. The same day in the evening the same again, that made it obvious it was not me. In the next few days the same kept happening at random times but never when I was there, and because it would turn on with the mute set I could not hear when it happened.

Finally one day it was off, I went to the kitchen and when I came back it was on and muted again, so I guessed a relation had to exist. Turned it off and went to the kitchen again - no joy. Repeated a few times and surprise - again on and muted. Some more experiments revealed that switching off the kitchen light sometimes would cause the SABA to turn on and activate the mute at the same time.

The kitchen light consists of two 36W fluorescent tubes, apparently the inductive kick at turn off found its way into the SABA digital controls. They were two rooms apart, so not exactly next to the kitchen switch or lights. The issue did not reoccur after I plugged the printer back.

 

[Jeff Liebermann]

How to operate a tube caddy.

During the early 1970's, I ran a 2way radio service shop. Running it
was an accident because no sooner was I hired, everyone else either
quit or promoted themselves sideways, leaving me as the sole employee
and later as part owner. This condition lasted for a few months of
serious overwork, until I was finally able to hire an employee. The
shop:
<http://802.11junk.com/jeffl/pics/Old%20Repeaters/slides/PMC02.html>

A major part of the operation was maintaining a mountain top radio
repeater site:
<http://802.11junk.com/jeffl/pics/Old%20Repeaters/slides/Santiago-01.html>
When something went wrong, the ritual was to load up the company
pickup truck with everything imaginable, drive 12 surface miles to the
base of the mountain, drive 16 miles up a windy dirt road to the top,
fix something, and repeat the ritual in reverse. 6 to 8 hrs was the
typical round trip time.

Replacement tubes were carried in a tube caddy. For those who have
never seen a tube caddy, the individual tubes were stored in small
personalized cardboard boxes, inside a wooden carrying case like
these[1]:
<https://www.google.com/search?q=tube+caddy&tbm=isch>
My new employee would identify the dead or dying tube, extract a new
tube from the tube caddy, insert the new tube into the radio, insert
the dead tube into the cardboard box, and replace the box into its
place in the tube caddy. Do you see a problem here?

That worked for about 3 months when I discovered that my new employee
couldn't seem to fix anything. Various theories were offered, but
nothing worked. One day, my employee had a cold, so I had to do the
drive up the mountain. Oddly, I also couldn't seem to fix anything
either. Then, I noticed that some of the tubes I was using as
replacements were obviously ancient and really didn't belong in
service. Hmmm...

Upon returning to civilization, I tested almost all the tubes in the
tube caddy, and found that well over half were dead[2]. When I
mentioned it to my new employee, it took him a while to understand
what had happened. I suspected that the thought the tube caddy
somehow rejuvenated dead tubes. I resisted the temptation to thrash
him about the head, because he was bigger than me. I later found him
a job with a competitor.


[1] I still have a tube caddy full of tubes awaiting the demise of
semiconductors.

[2] Tube testing algorithm. If the tube tester says it's bad, it's
bad. If the tube tester says it's good, it still might be bad.


--
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