Author Topic: Dave's fault finding technique and other stuff.............  (Read 18720 times)

0 Members and 1 Guest are viewing this topic.

Offline Bored@Work

  • Super Contributor
  • ***
  • Posts: 3932
  • Country: 00
Re: Dave's fault finding technique and other stuff.............
« Reply #50 on: June 19, 2014, 03:25:26 pm »
It is relatively simple. Someone is talking bull. I haven't seen a classic TV or audio equipment repair shop in the past (when stuff was still repaired) where they didn't have e.g. a transistor substitution book. Part substitutions were done regularly - with or without the help of a substitution list. And not only electronic parts, but also mechanical parts.

So much for
- Never change the design of a circuit or 'band-aid" components.
I delete PMs unread. If you have something to say, say it in public.
For all else: Profile->[Modify Profile]Buddies/Ignore List->Edit Ignore List
 

Offline crispus

  • Regular Contributor
  • *
  • Posts: 113
  • Country: ro
Re: Dave's fault finding technique and other stuff.............
« Reply #51 on: June 19, 2014, 06:21:52 pm »
Why the video is private?
I know I'm numskull, but I look around me and I feel better.
 

Offline FireBird

  • Regular Contributor
  • *
  • Posts: 56
  • Country: at
Re: Dave's fault finding technique and other stuff.............
« Reply #52 on: June 19, 2014, 07:21:01 pm »
I have no problem to access this video. Or are you talking about #632? It had to be temporarily removed because the video had a flaw.

 

Offline DJ

  • Supporter
  • ****
  • Posts: 129
  • Country: us
Re: Dave's fault finding technique and other stuff.............
« Reply #53 on: June 19, 2014, 07:50:59 pm »
It is relatively simple. Someone is talking bull. I haven't seen a classic TV or audio equipment repair shop in the past (when stuff was still repaired) where they didn't have e.g. a transistor substitution book. Part substitutions were done regularly - with or without the help of a substitution list. And not only electronic parts, but also mechanical parts.

So much for
- Never change the design of a circuit or 'band-aid" components.

For the repair persons perspective,  not substituting / changing is generally good advice.

When I design something,  I may be going through all sorts of worst-case,  derating or other analyses that lead to the specification of a certain part (or alternatives as I will put in each component specification sheet, which is internal only). Changing a part may work short term, but may also lead to unintended consequences.  In general,  better parts are usually ok, as long as one understands what specs are important.  It may be more than value/Tolerance/power/voltage, etc.

On the other hand,  designers and often parts sourcing make mistakes. Sometimes a different part will work better. It is incumbent on the person doing the work to clearly understand a circuit before taking that step.

I will say from a designer's perspective,  that I love to have techs, users and other engineers tear my stuff apart. Much better in the long run for quality product.

 

Offline What_NZ

  • Regular Contributor
  • *
  • Posts: 150
  • Country: nz
Re: Dave's fault finding technique and other stuff.............
« Reply #54 on: June 19, 2014, 09:02:05 pm »
It is relatively simple. Someone is talking bull. I haven't seen a classic TV or audio equipment repair shop in the past (when stuff was still repaired) where they didn't have e.g. a transistor substitution book. Part substitutions were done regularly - with or without the help of a substitution list. And not only electronic parts, but also mechanical parts.

So much for
- Never change the design of a circuit or 'band-aid" components.

This would have made a better question than a statement.
Transistor substitution is not considered as changing the design (generally). Even companies like Panasonic published such books, many Sanyo Service Manuals actually listed the substitutions in the parts list for the technician. What is important, is the ability of the technician to understand the design of the circuit. For general purpose transistors there is usually no harm in substituting and the designer will have just selected one of many possibilities, probably based on his past familiarity with its specification, cost, availability etc so generally no harm there...... However it is a different story when the transistor has been selected for a critical reason i.e. its specification is why the circuit operates or will continue to operate correctly. Replacing with a substitute part can be a trap that leads you around in circles.
Are you an Electronics Technician in the service industry? because I would have thought you would have encountered a situation already, where substituting a transistor (even from a book) failed to work correctly in the circuit you were repairing. Hence my advise to "Never change the design of a circuit or 'band-aid" components. As you are not the designer........."
« Last Edit: June 19, 2014, 09:22:39 pm by What_NZ »
 

Offline What_NZ

  • Regular Contributor
  • *
  • Posts: 150
  • Country: nz
Re: Dave's fault finding technique and other stuff.............
« Reply #55 on: June 19, 2014, 09:18:48 pm »
It is relatively simple. Someone is talking bull. I haven't seen a classic TV or audio equipment repair shop in the past (when stuff was still repaired) where they didn't have e.g. a transistor substitution book. Part substitutions were done regularly - with or without the help of a substitution list. And not only electronic parts, but also mechanical parts.

So much for
- Never change the design of a circuit or 'band-aid" components.

For the repair persons perspective,  not substituting / changing is generally good advice.

When I design something,  I may be going through all sorts of worst-case,  derating or other analyses that lead to the specification of a certain part (or alternatives as I will put in each component specification sheet, which is internal only). Changing a part may work short term, but may also lead to unintended consequences.  In general,  better parts are usually ok, as long as one understands what specs are important.  It may be more than value/Tolerance/power/voltage, etc.

On the other hand,  designers and often parts sourcing make mistakes. Sometimes a different part will work better. It is incumbent on the person doing the work to clearly understand a circuit before taking that step.

I will say from a designer's perspective,  that I love to have techs, users and other engineers tear my stuff apart. Much better in the long run for quality product.
Thanks and I would say you said it better than me.
Yes, I have seen huge cock-ups in production where parts sourcing substituted a part. Problems with testing had the design engineer  stomping through the testing area mumbling "Why the f__k do they employ me, when they know it all." the rework alone was 10's of thousands just because of one transistor but unfortunately it was used in multiple places.
In general I found design engineers extremely interesting people to talk with, there was always something to learn about why they designed a circuit this way or that. Can be amusing when you see an experienced engineer and one freshly out of university looking over a circuit, the young guy all cocky with new knowledge and the experienced engineer saying "they may teach you to do it like that, but in the real world ........."
« Last Edit: June 19, 2014, 09:28:16 pm by What_NZ »
 

Offline Bored@Work

  • Super Contributor
  • ***
  • Posts: 3932
  • Country: 00
Re: Dave's fault finding technique and other stuff.............
« Reply #56 on: June 19, 2014, 10:11:20 pm »
In a repair shop it didn't matter what a designer wanted or desired. You were never going to meet that guy, and you gave a fart about who that guy was. And frankly, the designer was surly giving a fart about any repair technician and had moved on to many other projects.

What matters was the customer breathing down your neck. You found a defect transistor, you didn't stock it? So you turned to the substitution list and were happy if you had one of the suggested substitutions in stock. In it went. Fault was fixed. Customer happy. Customer paying.

That was the reality in every such shop I happened to know. So don't give me this repair technician trainer bull. You know nothing about the reality in a repair shop. So your lecture attempts here are a joke.
I delete PMs unread. If you have something to say, say it in public.
For all else: Profile->[Modify Profile]Buddies/Ignore List->Edit Ignore List
 

Offline What_NZ

  • Regular Contributor
  • *
  • Posts: 150
  • Country: nz
Re: Dave's fault finding technique and other stuff.............
« Reply #57 on: June 19, 2014, 11:24:38 pm »
In a repair shop it didn't matter what a designer wanted or desired. You were never going to meet that guy, and you gave a fart about who that guy was. And frankly, the designer was surly giving a fart about any repair technician and had moved on to many other projects.

What matters was the customer breathing down your neck. You found a defect transistor, you didn't stock it? So you turned to the substitution list and were happy if you had one of the suggested substitutions in stock. In it went. Fault was fixed. Customer happy. Customer paying.

That was the reality in every such shop I happened to know. So don't give me this repair technician trainer bull. You know nothing about the reality in a repair shop. So your lecture attempts here are a joke.
Wow so protective. So what did I say wrong? I didn't disagree with you. I just expanded as to why it may or may not be a good idea to substitute parts, Transistors was the example.
You have your experiences/knowledge of a repair shop and I have mine of the industry. I am not going to say you don't know what you are talking about so please don't say that of me either. I am trying to make this general information for the home hobbyist or amateur repairer. Of course it may not fit the experience of a tech working in a shop somewhere.
 

Offline onlooker

  • Frequent Contributor
  • **
  • Posts: 384
Re: Dave's fault finding technique and other stuff.............
« Reply #58 on: June 20, 2014, 01:28:07 am »
Like many others felt, the video was entertaining for me. I never expected everything to be perfect with such a one person crew.

The only point made me nerves to watch was that Dave leaned the LCD screen on a corner of one of his test gears while pressing and tapping on the other side. I think maybe it is better to re-attach the TV stand after taking off the back cover. Anyway, that was what I did when I did my own repair of my 46" LCD TV recently (spanning 6 months, on and off).
 

Online EEVblog

  • Administrator
  • *****
  • Posts: 29697
  • Country: au
    • EEVblog
Re: Dave's fault finding technique and other stuff.............
« Reply #59 on: June 20, 2014, 02:08:43 am »
I think maybe it is better to re-attach the TV stand after taking off the back cover.

You can't with this model, I tried. It screws into the back cover.
 

Offline vk6zgo

  • Super Contributor
  • ***
  • Posts: 4868
  • Country: au
Re: Dave's fault finding technique and other stuff.............
« Reply #60 on: June 20, 2014, 05:48:24 am »
I found that the substitution lists were not always very helpful,as they often had typos & other errors.
Another thing was,depending on their origin,they often had little or no coverage of the other naming conventions (JEDEC-v- the rest).

I tended to look at what other manufacturers used in similar circuits.
For instance,if Philips used a particular Horizontal output transistor in a very similar circuit to the one Sony used,there was a pretty good possibility it would work OK in the Sony circuit.

Fixing Monitors,TVs,etc is not my main line of work,as I was mainly a Transmitter Tech.
That is an occupation with a broad streak of "bush mechanic",as you are always "under the hammer" to restore services.

With my earlier Employer,Telecom Aust,we had the contract to operate, maintain & repair the ABC Transmitters,as well as those of a major regional Commercial TV Network.

In one site,this company had a Thomson-CSF TV Transmitter.
The power supply for the Transistor PA's (TRPAs in NEC jargon) "let the smoke out" in a big way,so they had to go down in power to the 1kW LGT standby.

New parts from France?---Several weeks at the least!

It just happened that a similar supply for the TRPAs of an ABC NEC Tx was sitting as an extra spare at the Bickley site.
The guys from the other site grabbed it,(with permission),tweaked the voltage settings to match the Thomson,sat it outside the Tx ,as it wouldn't fit inside,wired it up (with due care as to safety).
They fired up the Thomson,& up it came,full power back---all good!

That power supply sat there for months before the parts arrived for the original one!
 

Offline What_NZ

  • Regular Contributor
  • *
  • Posts: 150
  • Country: nz
Re: Dave's fault finding technique and other stuff.............
« Reply #61 on: June 20, 2014, 06:47:20 am »
I found that the substitution lists were not always very helpful,as they often had typos & other errors.
Another thing was,depending on their origin,they often had little or no coverage of the other naming conventions (JEDEC-v- the rest).

I tended to look at what other manufacturers used in similar circuits.
For instance,if Philips used a particular Horizontal output transistor in a very similar circuit to the one Sony used,there was a pretty good possibility it would work OK in the Sony circuit.

Fixing Monitors,TVs,etc is not my main line of work,as I was mainly a Transmitter Tech.
That is an occupation with a broad streak of "bush mechanic",as you are always "under the hammer" to restore services.

With my earlier Employer,Telecom Aust,we had the contract to operate, maintain & repair the ABC Transmitters,as well as those of a major regional Commercial TV Network.

In one site,this company had a Thomson-CSF TV Transmitter.
The power supply for the Transistor PA's (TRPAs in NEC jargon) "let the smoke out" in a big way,so they had to go down in power to the 1kW LGT standby.

New parts from France?---Several weeks at the least!

It just happened that a similar supply for the TRPAs of an ABC NEC Tx was sitting as an extra spare at the Bickley site.
The guys from the other site grabbed it,(with permission),tweaked the voltage settings to match the Thomson,sat it outside the Tx ,as it wouldn't fit inside,wired it up (with due care as to safety).
They fired up the Thomson,& up it came,full power back---all good!

That power supply sat there for months before the parts arrived for the original one!

RF equipment was not really my area of expertise, actually to be honest I was always a bit scared of it, well the TX part of it anyway. Panasonic sold at various times some Marine Radio's. I can't remember exactly why but they had an unusually high number of dry joints so we saw quite a few of them, got my second RF burn from the output of one of them and it hurt like a bugger for weeks. The equipment I worked on was a toy compared to what you were servicing also a different set of skills and safety concerns to work on high powered RF equipment.
So thanks for sharing. I always like hearing about servicing in areas I was never involved with. Just shows how diverse the industry is.
« Last Edit: June 20, 2014, 07:59:04 am by What_NZ »
 

Offline gildasd

  • Frequent Contributor
  • **
  • Posts: 926
  • Country: be
  • Engineering watch officer - Apprentice Officer
    • Sci-fi Meanderings
Re: Dave's fault finding technique and other stuff.............
« Reply #62 on: June 20, 2014, 07:00:09 am »
Everybody has their own approved technique.

"Licks finger, sticks it in plugged TV set while humming to himself"

If the humming stops, the voltage drops.
I'm electronically illiterate
 

Offline Joule Thief

  • Regular Contributor
  • *
  • Posts: 249
  • Country: us
Re: Dave's fault finding technique and other stuff.............
« Reply #63 on: June 20, 2014, 08:39:20 am »
Said it before and I'll say it again,

I come for the entertainment and I stay for the - well - the aftermath and diversity of opinions - yeah, that's the ticket !   :-DD
Perturb and observe.
 

Offline AlphZeta

  • Regular Contributor
  • *
  • Posts: 244
  • Country: us
    • Kerry D. Wong
Re: Dave's fault finding technique and other stuff.............
« Reply #64 on: June 20, 2014, 10:55:32 pm »
One thing I like about EEVblog forrum is these often heated debates!

To Dave's defense, he has to make the video interesting enough to get his audience energized and engaged. Don't forget, this is his full time job :). I am sure he could easily have done a lot of his videos with just some very basic equipment, but then we would have missed all the fun!

Most of the time he uses those high-end and expensive equipment just because he has them (as he said, for kicks). Yes, for most repairs, a good analog multimeter, a half-decent digital multimeter and a scope will do the trick. I myself tend to be on the other side of the spectrum, using only the simplest tools I have but I am sure if I have those high end equipment, I'd use them just for fun as well.
 

Offline HighVoltage

  • Super Contributor
  • ***
  • Posts: 4252
  • Country: de
Re: Dave's fault finding technique and other stuff.............
« Reply #65 on: June 22, 2014, 09:03:27 am »
I have learned something from every repair video that Dave has done.
What more can I ask for?

Everyone of us has different ways to go about finding a problem.
Dave has one more challenge: He has to make it entertaining.
Imagine Dave would find the fault in 30 sec.... the video would be boring and over.


There are 3 kinds of people in this world, those who can count and those who can not.
 

Offline george graves

  • Super Contributor
  • ***
  • Posts: 1259
  • Country: us
Re: Dave's fault finding technique and other stuff.............
« Reply #66 on: June 22, 2014, 10:49:42 am »
I have learned something from every repair video that Dave has done.
What more can I ask for?

Same here.  I learned a lot to on that TV repair.  It wasn't my favorite video - but it was worth putting on in the background while I assessabled a small batch of stuff.

PS - somewhere these is a Dave "rant" on a walk (drive? - think it was a walk in a park or soemthing) that Dave gave about how he's "Not a bloody TV repair man!!!!"

Anyone have a link to that?  That would be funny about now!  Love ya Dave!


Online EEVblog

  • Administrator
  • *****
  • Posts: 29697
  • Country: au
    • EEVblog
Re: Dave's fault finding technique and other stuff.............
« Reply #67 on: June 22, 2014, 11:02:02 am »
Dave has one more challenge: He has to make it entertaining.
Imagine Dave would find the fault in 30 sec.... the video would be boring and over.

Well, that's the trick, which is why I'll throw out a speculator at the start to make it interesting rather than just say "I have absolutely no idea" lest I look a fool, likely involving common issues in repairs, such as the capacitors in this example which followed the symptoms.
So that means I go inside and check those caps I just mentioned straight away in order to keep the continuity there.

This was essentially 10 minutes tops of actual troubleshooting for I found the fault, so it's hardly dicking around not finding anything, it was a very quick and efficient repair. But the problem comes in when you try and shoot a video about it in "real time", and you end up with a much longer video. And in this case, a split video because that extra time setting up filming the first part of the video meant I ran out of time and had to go home. So it turned into a two parter.
 

Offline Kjelt

  • Super Contributor
  • ***
  • Posts: 5655
  • Country: nl
Re: Dave's fault finding technique and other stuff.............
« Reply #68 on: June 22, 2014, 02:23:29 pm »
Still I admire his balls for putting that video on the air, showing he is not infallible and still making his point.
I don't see any "balls" in releasing this at all.
I was referring to a previous video where you were demoing solderpaste and stencilling technique from free_electrons book not this video ;)
 


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf