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.

On 03/12/2015 12:34, Mark Zacharias 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.

My favourite was the car audio cassette player, ie no record function.
It recorded vinyl record clicks on to any prerecorded tape played in there.
Answer at end of spoiler defeat, run of +








+













+










+













+



























The pinch wheel had a tiny piece of magnet fragment embedded in it

Mark Zacharias 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?

My first computer was a Franklin Ace 1000 that was give to me broken. It
had complete schematics so I was able to trace out what was in fact a bad
reset signal going to the CPU. Pretty sure it was a 74S161 (something that
ran hot and wasn't LS series) that had to be swapped out and it was fine
again. Donor chip came from an arcade machine board. Looking that part up
I see it's a 4 bit counter- if that's correct it may have someting to do
with the video timing signals which were a weird hack in the Apple ][
which this machine was an improved clone of.

On 3/12/2015 11:34 PM, Mark Zacharias 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.

**I recall the first time (1980-ish) I discovered those fusible
resistors that go high after a few years. With no obvious signs of
distress. Now I just head straight for the buggers.

Then there's those low value (/=47 Ohms), 1/4W cracked carbon resistors
that go O/C when subjected to ca. 60+ Volts with no signs of burning
(Marantz 1200b, 240, 250M, 500 models). Over the years, I learned to
suspect any resistor over the value of 100k, if the circuit is
displaying some kind of mysterious fault that cannot be explained by a
semiconductor failure or cap leakage.

--
Trevor Wilson
www.rageaudio.com.au

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

On Fri, 4 Dec 2015 06:49:10 +1100, Trevor Wilson
wrote:

On 3/12/2015 11:34 PM, Mark Zacharias 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.

**I recall the first time (1980-ish) I discovered those fusible
resistors that go high after a few years. With no obvious signs of
distress. Now I just head straight for the buggers.

Then there's those low value (/=47 Ohms), 1/4W cracked carbon resistors
that go O/C when subjected to ca. 60+ Volts with no signs of burning
(Marantz 1200b, 240, 250M, 500 models). Over the years, I learned to
suspect any resistor over the value of 100k, if the circuit is
displaying some kind of mysterious fault that cannot be explained by a
semiconductor failure or cap leakage.
That resistor story is interesting. About two years ago I had a linear
power supply fail in one of my CNC machines. I did the troubleshooting
bit and discovered a bad -15 volt regulator. So I replaced it and then
a few weeks later something else went bad and I couldn't find it. I
took it to a friend who is an electronics engineer and he discovered
an open resistor. I asked why he checked it because there was no
visual reason for it to be bad. It wasn't cracked or discolored. He
said that's what he usually did first, check for open resistors. He
said it was a common fault. Since then the power supply has been
operating fine.
Eric

wrote in message
...
On Fri, 4 Dec 2015 06:49:10 +1100, Trevor Wilson
wrote:

On 3/12/2015 11:34 PM, Mark Zacharias 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.

**I recall the first time (1980-ish) I discovered those fusible
resistors that go high after a few years. With no obvious signs of
distress. Now I just head straight for the buggers.

Then there's those low value (/=47 Ohms), 1/4W cracked carbon resistors
that go O/C when subjected to ca. 60+ Volts with no signs of burning
(Marantz 1200b, 240, 250M, 500 models). Over the years, I learned to
suspect any resistor over the value of 100k, if the circuit is
displaying some kind of mysterious fault that cannot be explained by a
semiconductor failure or cap leakage.
That resistor story is interesting. About two years ago I had a linear
power supply fail in one of my CNC machines. I did the troubleshooting
bit and discovered a bad -15 volt regulator. So I replaced it and then
a few weeks later something else went bad and I couldn't find it. I
took it to a friend who is an electronics engineer and he discovered
an open resistor. I asked why he checked it because there was no
visual reason for it to be bad. It wasn't cracked or discolored. He
said that's what he usually did first, check for open resistors. He
said it was a common fault. Since then the power supply has been
operating fine.
Eric



Yeah - when "the usual suspects" don't pan out, I start looking for bad high
value resistors.

Had a bad 150K 1/8 watt carbon on a late model Pioneer surround receiver the
other day.


Mark Z.

On 12/3/2015 6:34 AM, Mark Zacharias wrote:


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


Mark Z.

I posted this an hour ago, but it hasn't shown up, so I'll do it again.

Back 30 years ago I stopped at a consumer electronics/TV repair shop
and presented my resume. I had been to many manufacturer service
training seminars and had a hand full of certificates of completion. The
owner looked it over and said, "I just hired a guy, I wish you came in
earlier." So I went home and about 45 minutes later he called and said,
"I see you have a lot of Sony training, I have this projection TV in
here that nobody can fix, I'd be happy to pay you for looking at it."
So I drove down and got the manual, noted the problem was, no output
from the 3 tubes. I started poking around in the HV section, and within
minutes the owner said, hey you got it working! I didn't know it was
working ;-} I put my head out front and it had an output.
Hmm, I unhooked my scope probe and the picture went with it.
From there, we, more he, figured out one of the other techs replaced a
cap with 1/10 the proper value, the scope probe hanging on the test
point had enough capacitance to make the set work.
He hired me that day, it was good, within two blocks of my house.
So, I got a job by accident.
Mikek

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/pop...lectronics.htm

Have fun

Mark







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

On Thursday, December 3, 2015 at 12:34:56 PM UTC, Mark Zacharias 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.



My favourite - I was working for a Pro PA hire compoany in London. They had supplied a monitor system for a BBC recording of Public Image Ltd at Maida Vale Studios, London. The system was buzzing like crazy and none of the Sound Company or BBC engineers could work out why. They were about to pull the whole gig.
They sent me down as a last faint hope.

It was obviously some kind of mains problem, but everything seemed to check out fine on multimeters. Earths, Neutrals were all at 0v.
Eventually I decided to plug in my scope, to discover that instead of a nice straight line accross the display, it was massively modulated.
Clearly the scope's Earth wasn't a proper Earth but had some mains on it.
I then was able to track down the fault - one multi-way extension cable attatched to the many, many pieces of equipment had Earth and Neutral reversed, thus connecting all Earths and Neutrals in the middle of the studio as well as back at the mains Intake.

Ripped the offending extension out, the buzzing ceased immediately, and the BBC and Public Image Limited got their recording and the Sound Company didn't lose the gig or it's reputation.



Gareth.

On Thu, 3 Dec 2015 06:34:55 -0600, "Mark Zacharias"
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.

Last one. There were these very expensive ADS cd players which would
play any disc except a ,very popular at the time, Jimi Hendrix Ryko
disc. Couldn't find any electronic or mechanical problems. I slightly
moved the CD turntable slightly down on the spindle and this disc and
all other discs would play.

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

On Thursday, December 3, 2015 at 7:34:56 AM UTC-5, Mark Zacharias 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 one pops to mind took couple of years off my life. It was an old Hitachi built RCA projection TV (circa 1981) that had blown fuses in the power supply, but nothing showed a short resistance wise. I replaced the fuses and it powered up, only the geometry didn't look right. When I went to connect the cable back on to it to see exactly what the picture was like a blinding flash and arc appeared at the RF connector and it blew the fuses again. Working pretty much on my stomach in a cramped house, I traced a hot side/cold side short all the way back to the end of the line, which was a leaky deflection yoke (vert winding to horiz winding). It seems the horiz winding was on the hot side of the chassis and the vert winding was on the cold side. How it didn't blow the vert IC or horiz deflection output is a mystery.

"Chuck" wrote in message
...
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.


Many electronic devices will have a common problem. It may take a while to
find it,but once found, the first thing to look for.

I worked for a large company and we had a new building built and equipment
installed. All was fine for a while, the some heaters for the process got
where they would not come on if cut off. I was the first one to get a call
about this. Took about 2 or 3 hours to troubleshoot this as it was the
first time anyone had worked on it. Found a bad plug in time delay relay
was bad. After that a simple one point voltage check would usually tell the
relay was bad. Next time it only took seconds to change out the relay and
was usually done any time they would not come on. 99.9% of the time that
was the problem. As that place operated 24 hours a day, the peopel in
production was told about it and told the electrician that showed up to
change it out if they did not know what the problem might be. Saved lots of
late night phone calls.

On 12/3/2015 6:34 AM, Mark Zacharias 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.

In the late 80s early 90's I worked on VCR's. The Fisher FVH 906,
had a tuner that went defective, no schematic, a replacement part only.
That's ok under warranty, but after that, the part cost was to high to
get a repair ok. So one day, I decided to see if I could find out what
the cause of the failure was. I started spraying parts with freeze mist
and found when I hit a 1uf 35V cap the picture came back. I made a lot
of repairs, replacing that same cap on a whole bunch of tuners.
I'd do the same thing every time, dribble 2 or 3 drops of freeze mist
on the cap and the picture came in.

I had a customer bring in a remote for repair, it checked out fine.
He took it home and called saying it didn't work. I talked to him a bit
and found he had just install new CFL lights. I suggested he shield that
light and try it. It worked, I had just read about that in a trade
magazine two days previous.
Mikek

I got in early on the VCR curve, they were expensive, commanding high
service rates, then when prices dropped we had a high volume of repairs,
rode it down until the price was close to $200, then I moved to Florida.
A year later the tech that took my place said he came in a couple days
a week to repair the few that came in. I repaired a little over 11,000
vcr's in ten years, it was a good time.

wrote:


I then was able to track down the fault - one multi-way extension
cable attatched to the many, many pieces of equipment had Earth
and Neutral reversed, thus connecting all Earths and Neutrals
in the middle of the studio as well as back at the mains Intake.

Ripped the offending extension out, the buzzing ceased immediately,
and the BBC and Public Image Limited got their recording and the
Sound Company didn't lose the gig or it's reputation.



** I know of a similar example involving a 30kW, 3 phase lighting system for live entertainment here in Sydney. Was back when lighting consoles communicated
with triac dimmer racks via 0-10V analogue signals.

The system seemed to have a mind of its own, lights came up and varied about with all faders set to zero. Bringing one fader up affected many others.

After hours of fruitless searching, the culprit was identified as the AC plug on the lighting console itself which had neutral & earth reversed.

Seems a roadie had fitted a new plug after accidentally damaging the original and told nobody.


..... Phil

Mark Zacharias 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.

One of my first chances to stick my chest out and strut was shortly after I
checked aboard my first duty ship during my stint in the Navy in mid-1964.
Barely 20 years old, I was assigned to overhaul & repair of UHF shipboard
radio transmitters.

The ship had a small calibration lab, which was staffed by a PO1, a PO2s and
a couple PO3s (POs are Petty Officers... enlisted men) who had all been to
the elite Air Force PMEL calibration school in Colorado. One day, after all
the cal lab techs had a shot at it and several of the other bench techs had
also been called in to try fixing it,, I was called in to take a shot at
repairing a new HP 524D 10MC digital counter from another ship. It just
wouldn't show any indication of trying to count... all the displays just
sat at zero no matter what the input signal looked like.

I sat down and took a look at the schematic, hooked a scope probe to the
output of the gate tube, a 6AL5. No pulses. Hooked the probe to the gate
input to the gate tube. Good gate pulses. Hooked the probe to the signal
input of the gate tube. Good squared pulses that followed the frequency of
the input signal.
I asked for a 6AL5 tube, plugged it in, and Voila! everything came to life.

Made me feel kinda good that it only took me about 10 minutes to fix what
had stumped 9 or 10 good techs for several days. From that day until now, I
have had an affinity for test instruments, especially those used for time &
frequency measurement.

Dave M

Mark Zacharias 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?


** Ok, here is a wacky one:

I once had a customer who rented out DJ systems: turntable & mixer consoles, stereo amps and speakers. DJs back then owned a collection of LPs and generally rented audio gear on a daily basis.

So I got this TT console with the complaint while it started off OK, it was losing volume & changing tone after a while becoming duller and duller until full treble was needed to correct it.

The story sounded dubious, but I checked out the mixer thoroughly using hot air and an all day soak test - result negative, it worked fine all the time.

Handed it back to the hire business guy and a week later it was returned with the SAME complaint plus some hostility that I had clearly not fixed it. Naturally it passed all tests again.

I had a chat with the hire guy and he agreed to use the console himself at a gig and of course it worked fine all night. Next time it went out on hire, he got the same complaint from the same DJ - who was by now ropable that nothing had been done about the problem.

So my hire guy paid a visit to the venue where the gear was being used, his first. When he walked in, he was nearly deafened by the volume and the sound was absurdly shrill. On approaching the DJ and noticing that volume and treble controls were all maxed out - he was told:

" See what I mean ??

Sounds **** weak and there's no treble."



..... Phil

Chances are he'll never hear his grandkids cry.

On Thu, 03 Dec 2015 06:34:55 -0600, Mark Zacharias wrote:

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

Somewhere in the eighties we installed a custom-built control system in
a 24/7 assembly line for SIL ceramic hybrid circuits.
Subcontractor of subcontractor job.

One night I was called in for an unexpected stop.
Inside the plant I was 'greeted' by the crowd of tech support people and
blaming managers gathered around our equipment.
On my way to the control system I came across one of the typical mushroom
emergency stops along the production line.
By habit I twisted the knob and felt the release spring.
I worked my way to the control panel and engaged the start.
Within seconds the crowd silenced and fled the scene: the line was up.

We were never again called in.

"c4urs11" wrote in message
...
On Thu, 03 Dec 2015 06:34:55 -0600, Mark Zacharias wrote:

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

Somewhere in the eighties we installed a custom-built control system in
a 24/7 assembly line for SIL ceramic hybrid circuits.
Subcontractor of subcontractor job.

One night I was called in for an unexpected stop.
Inside the plant I was 'greeted' by the crowd of tech support people and
blaming managers gathered around our equipment.
On my way to the control system I came across one of the typical mushroom
emergency stops along the production line.
By habit I twisted the knob and felt the release spring.
I worked my way to the control panel and engaged the start.
Within seconds the crowd silenced and fled the scene: the line was up.

We were never again called in.

About 1981 I was still in tech school and not even really a technician yet.

(I was SO green).

Third semester, servicing phase. There was an old GE tube chassis color set
with intermittent color sync. It was a "re-do" which the prior class had
failed to fix correctly.

I got to the burst gate amp and saw there was a much smaller signal at the
grid than called for.

Also, there was a neon lamp in the grid circuit which was supposed to drop
75 or so volts and the drop was much higher than expected, plus the lamp
glowed somewhat faintly at it's base instead of lighting fully.

I couldn't get the instructor to order a miserable 75 cent neon lamp. He
kept me running around checking this cap or this resistor, etc.

Finally I went around him to another instructor, explained my logic and got
the lamp ordered.

Fixed the tv. My instructor never really forgave me for that.


Mark Z.

Things that are second nature to us now were "learning experiences" back
then, yes?

At my first job as a tech, about the second piece I ever worked on was a
Pioneer SX-828.

Yup - the infamous "blue Sanyo cap" scenario.

Except I had never heard of that and had no tech support or even a more
experienced tech along side me.

I was totally on my own, as I usually was during the first 15 or 20 years of
my career.

Symptom: one channel gone, just a low hiss. Preamp issue.

Tracing signal - got it, don't got it, and so on.

In the tone amp, DC voltage low at collector of one transistor.

1.5uF Sanyo coupling cap to base was leaky, driving that stage into
saturation.

Felt really good about that one.


Mark Z.

On Friday, December 4, 2015 at 1:53:47 PM UTC-5, Ralph Mowery wrote:
"Chuck" wrote in in sci.electronics.repair in message
...
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.

Many electronic devices will have a common problem. It may take a while to
find it,but once found, the first thing to look for.

Most of them have microchips (that you can't open up and repair). And they have software and wireless or hard wired connections to larger facilities elsewhere where techs can come in and review the software.

Many problems seem to be caused from malware or spyware (maybe some even from the government or other places) that intentionally interferes with the intended software provided by the company on the package's label.

I worked for a large company and we had a new building built and
equipment installed.

Right now, I'm not even working. I'm just sitting around looking at space cartoons and video games.

On 12/5/2015 6:52 AM, Mark Zacharias wrote:
Things that are second nature to us now were "learning experiences" back
then, yes?

At my first job as a tech, about the second piece I ever worked on was a
Pioneer SX-828.

Yup - the infamous "blue Sanyo cap" scenario.

Except I had never heard of that and had no tech support or even a more
experienced tech along side me.

I was totally on my own, as I usually was during the first 15 or 20
years of my career.

Symptom: one channel gone, just a low hiss. Preamp issue.

Tracing signal - got it, don't got it, and so on.

In the tone amp, DC voltage low at collector of one transistor.

1.5uF Sanyo coupling cap to base was leaky, driving that stage into
saturation.

Felt really good about that one.


Mark Z.

I had an SX-828, bought it sometime in the early 70s.
Been so many years, I don't recall the problem, but
I tossed it about two years ago, just too much stuff.

Mikek

Here's one.

Onkyo cassette deck, circa 1986. Perhaps a TA-630 or some such.

Played just fine in PLAY mode.

In REC mode only, the auto-stop would trigger at random times.

Partially open bridge rectifier. One of those little black round ones. In
PLAY mode the voltages held up, but in REC mode the additional load of the
bias oscillator dropped the voltage enough to cause the problem.

Ripple waveform was definitive. Showed 1/2 wave pattern where it should have
been full-wave.


Mark Z.

On Sat, 5 Dec 2015 14:34:50 -0600, "Mark Zacharias"
wrote:

Here's one.

Onkyo cassette deck, circa 1986. Perhaps a TA-630 or some such.

Played just fine in PLAY mode.

In REC mode only, the auto-stop would trigger at random times.

Partially open bridge rectifier. One of those little black round ones. In
PLAY mode the voltages held up, but in REC mode the additional load of the
bias oscillator dropped the voltage enough to cause the problem.

Ripple waveform was definitive. Showed 1/2 wave pattern where it should have
been full-wave.


Mark Z.


These bridge rectifiers also caused weird problems in Onkyo receivers
of the 1980s.

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On Saturday, December 5, 2015 at 2:44:26 PM UTC-5, Jon Elson wrote in rec.crafts.metalworking:
OK, we got one of those fancy energy-saving washing machines. After a few
years, it started having trouble filling with water. I replaced the
solenoid valve assembly twice over about 6 months, and then started
invetigating deeper. The control board had a micro and about a dozen
electeromechanical relays on it. The one for the cold water valve
eventually developed contacts burned so bad that I was able to diagnose it.
I replaced it with a solid state relay, and all has been good for several
years. I gues the cold water valve gets cycled the most often, so that
relay got burned up first. No problem yet with any of the others.

Yeah, obviously a current relay or just that kind of an interface or something. Tell 'em about it, so they can buy you a whole new one.

You can't get anything if you stay silent. (I learned that the hard way)

On Fri, 4 Dec 2015 07:13:43 -0800 (PST), 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/pop...lectronics.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.

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On Fri, 4 Dec 2015 14:28:24 -0600, amdx wrote:

On 12/3/2015 6:34 AM, Mark Zacharias 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.

In the late 80s early 90's I worked on VCR's. The Fisher FVH 906,
had a tuner that went defective, no schematic, a replacement part only.
That's ok under warranty, but after that, the part cost was to high to
get a repair ok. So one day, I decided to see if I could find out what
the cause of the failure was. I started spraying parts with freeze mist
and found when I hit a 1uf 35V cap the picture came back. I made a lot
of repairs, replacing that same cap on a whole bunch of tuners.
I'd do the same thing every time, dribble 2 or 3 drops of freeze mist
on the cap and the picture came in.

I had a customer bring in a remote for repair, it checked out fine.
He took it home and called saying it didn't work. I talked to him a bit
and found he had just install new CFL lights. I suggested he shield that
light and try it. It worked, I had just read about that in a trade
magazine two days previous.
Mikek

I got in early on the VCR curve, they were expensive, commanding high
service rates, then when prices dropped we had a high volume of repairs,
rode it down until the price was close to $200, then I moved to Florida.
A year later the tech that took my place said he came in a couple days
a week to repair the few that came in. I repaired a little over 11,000
vcr's in ten years, it was a good time.


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.

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On Thu, 3 Dec 2015 06:34:55 -0600, "Mark Zacharias"
wrote:

Any more recent successs stories to brag about?
C'mon, don't we all enjoy patting ourselves on the back, really?
Mark Z.

I haven't bothered to write anything new, but in 1994, I scribbled
this list for Wired Magazine, which never bothered to print it or pay
me:
http://members.cruzio.com/~jeffl/nooze/support.txt
I'm not sure I could call these success stories, but since I got paid
for most of the repairs, I guess it qualifies as successful.


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

In article , en
says...

On Thu, 03 Dec 2015 06:34:55 -0600, Mark Zacharias wrote:

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

Somewhere in the eighties we installed a custom-built control system in
a 24/7 assembly line for SIL ceramic hybrid circuits.
Subcontractor of subcontractor job.

One night I was called in for an unexpected stop.
Inside the plant I was 'greeted' by the crowd of tech support people and
blaming managers gathered around our equipment.
On my way to the control system I came across one of the typical mushroom
emergency stops along the production line.
By habit I twisted the knob and felt the release spring.
I worked my way to the control panel and engaged the start.
Within seconds the crowd silenced and fled the scene: the line was up.

We were never again called in.

And what was the charge for that?

$1 for resetting the switch and $9,999.00 for knowing which one?

Jamie

In article ,
says...

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.

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While I was in a neighborhood visiting a nice looking girl, a friend of
hers ask if I could go over to their place and see why their portable
color TV near the door had messed up colors they could not remove.

I really didn't want to go and told them it would be a minimum of $20
bucks just to walk in, they accepted.

So I walked in and didn't even bother to turn the TV on. I reached up
on top of the TV set and removed the 9x6 Triaxal Speaker with a large
magnet on it, sitting there for what ever reason, I have no idea why.

I held my hand out for the money! They asked aren't you going to even
turn it on? I said, you can do that, they did and could not believe what
they saw. I took the money and said, have a good day now..

Jamie

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.


** Need more explanation for that one.


..... Phil

amdx wrote:

I had an SX-828, bought it sometime in the early 70s.
Been so many years, I don't recall the problem, but
I tossed it about two years ago, just too much stuff.

Heh, anyone else reading this, before you toss it, check ebay for the
completed listings on both working and non-working audio stuff from the
70's and 80's, it's nuts.

Even if that 828 was broke, it seems to fetch $100-$150 and the working ones
$200 on up.

Some of the top of the line ones from back then (pio sx-1980, sansui 5500 i
think) in the thousands. This isn't the old tube stuff like Fisher and
Marantz, just the popular solid state crap from the 70's and 80's.

The power amps and speakers don't follow but anything with receivers and
turntables from that period, you probably can make back what you paid for it
new, and then some.

-bruce

You can get them cheaper if you get lucky. Some of those three day auctions on eBay n ****. But there is quite a number of people who appreciate that old stuff. Like me, I see no reason my amplifier needs wifi. I knew we were going downhill when I saw an amp with an RJ-45. And to me, this new stuff mostly sounds like ****.

And I don't like the idea of 12 balsa wood speakers the quality of a 1966 table radio and one woofer. Stereo was invented because we got two ears. I might even tolerate quad, but 7.1 ? Nope. I have a hard enough time understanding the words in stereo and on TV I usually switch it to mono.

Anyway, the prices of some of this stuff are outrageous. A Marantz like my old one, $700. Look up the price of a Marantz 2385. A Pioneer SX-1980. (not sure but I think that was the most powerful receiver ever built) Recently a turntable went for $55,000. What's more I talked to my buddy and mentioned that and he told me they go higher, up into six figures.

And now, down in Sydney, Australia, Elton John was spotted in a record store buying albums. The guy can afford anything he wants but he wants a record player. (and logically, records of course)

There is quite the renewed interest in vinyl these days. Even youngins. Guys on AK for example talking about how they just got their teenager a turntable and an old vintage system. Sometimes for their college dorm if that is where they live, other times wherever.

In fact right now we are setting up something of a lab for this stuff. Distortion tester, standards to calibrate everything for power output measurements, and more to come. The idea here is to be sure the stuff is working right because when it is 40 years old it can have insidious problems that only distort a little and won't be noticed right away. And when you get them running really right, that old 1970s **** blows most of the new **** away.

Don't get me wrong, there is a high end still but if you think about 1979 dollars and a receiver is $400, how much would that be today ? Well, it IS. The same relative level of quality easily costs four times the money. What you get for $400 is like what you got for $79 back then, although THAT quality is a bit better.

Just not that much. Not enough for me.

I don't use it, but I got a Pioneer SX-850. No lid, no bottom, glass in front broke, tuning shaft bent. Power suppl.y board was broke in three places, needed work on that, one channel of the power amp and the preamp as well ! It works. It is a rag. It is filthy but everything works.

Not for sale.

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.

Sony 32" loses green and blue - adjust vertical height.

This was an interesting comedy of failure mode. Apparently when they came out with AKB a had to be done to the CRT aperture grill frame. It reflected too much. The CRT had just been replaced. The way I figure it they used a dud from a non-AKB set. When the pulses feeding the cathodes to detect the current got to the frame they reflected like all hell and told the circuit there was too much green, and then blue as the circuit drifted a bit and brought the lines over the metal. I found this out with the scope. I mean, there is no green but it is getting alot of green feedback. WTF !

And THEN, to adjust the vertical you use a service menu. Guess what color the numbers and letters are in that menu. They were not red but if you left the set on for a while all you had was red.

I got some good ones about cars too.

On Sat, 5 Dec 2015 18:52:34 -0800 (PST), Phil Allison
wrote:

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.


** Need more explanation for that one.


.... Phil
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.

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I almost want to say it was a fault, but it may have been the design. Really, when you talk old stuff, some things just did not exist back then. Things that cause more interference.

When working on older equipment, much older, I had to learn not to expect too much.

In that case with the Tandberg I would have gotten some line filtering. they make those all put together units you can put right at the AC input, light enough so you can cut the cord even and just glue them about anywhere, just make sure they are as close to the AC inlet as possible.

To figure it all out we woukld need the print for that Tandberg. I remember working on one R2R deck that had no microprocessor. It was all gates and comparators and all that. I think it was a 9200 ??? So that one probably would have been alright, no keyboard scanning or any of that, just a bunch of switches and flipflops and gates. and then the solenoid and relay drivers, oh and the current drivers for the eddy current motors.

Simple, I liked it. I fixed it. It got sold. It got damaged in shipping. We got ****ed. I wish I would have kept it but really, I have no tapes.

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 **** poor design.


..... Phil

En el artículo , Jeff
Liebermann escribió:

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

My first-ever call out to a Unix system was to this very message.

--
(\_/)
(='.'=) Bunny says: Windows 10? Nein danke!
(")_(")

On Sunday, December 6, 2015 at 5:24:04 PM UTC-8, Phil Allison wrote:

The light dimmer was putting an enormous amount of hash on the mains;
somehow it was getting into the microprocessor circuitry.

** Wall dimmers put large voltage spikes on the wiring...

Well shielded, low impedance gear is not affected but anything high impedance and not well shielded picks it up.

There's another possibility: knob/tube wiring puts those spikes on distant
HOT and NEUTRAL wires (not a close-spaced pair). So, there can be significant
magnetic induction, and that can mess up low impedance circuitry. It used
to be seen a lot in CRT television pictures as deflection jitter.

You have to worry about low impedance, too (balanced pair helps).

On Sun, 6 Dec 2015 17:23:59 -0800 (PST), Phil Allison
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 **** 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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