Author Topic: Dave's fault finding technique and other stuff.............  (Read 18485 times)

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Offline What_NZ

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Hi there,

I'm a long time watcher of Dave's video's and find most of the things he shows and talks about to be informative, for some strange reason I also enjoy mailbag too. I have no reason to doubt his credentials and life experiences, actually I'm a fellow atheist so I like the guy for that reason alone!
I didn't want to join the forum to be a basher and I hope this first post is not taken the wrong way. Dave is very good at what he does in other areas but fault finding has me thinking most of the time "WTF is he doing......" and the latest Soniq TV repair video was the proverbial straw!
I don't want to make this a rant so will just cut to what I taught Electronics Technicians for some 30 odd years as a Workshop Manager and Trainer for Panasonic.
Do not deviate from these important steps -

1/ Confirm the customers description of the fault, also confirm the correct functionality of overall operation
2/ Check visually the outside for anything unusual or signs of damage, physical damage, liquid ingress etc
3/ Open the unit and recheck customers description of the fault, also reconfirm the correct functionality of overall operation
4/ Start a complete visual inspection looking for anything unusual, charring, over heating, damaged components, corrosion, obvious dry joints

Next -

- Always be aware of jumping to conclusions and following garden paths, don't go too deep too quickly. Reassess every now and then, why and what I am doing.

There are a number of branches the next steps could follow depending on the fault but basically in no particular order -

- Check for intermittents, tap test, flexing the PCB either by hand (safety first of course) or an insulated object.
- Alternating between a can of Freeze and a Hair dryer can help to isolate temperature related faults. Also helpful are small gas powered hot air blowers for pin point heating, even the hot tip of a soldering iron can be useful (be careful it is grounded)

- If you need to start tracing a fault then start with Power supply, Oscillators, Resets
- Don't assume ground is contiguous throughout the whole unit. I have seen many a technician fooled by an open circuit/floating ground while testing another PCB from a common ground point. Shift the ground point to the Circuit/PCB you are testing or check the ground continuity.
- Never assume that just because you have voltage you don't have excessive ripple.
- Before replacing a fuse (of any type) ask yourself "why did it fail?" check the resistance of the circuit on the secondary side.
- Carefully unplug, check and reconnect all relevant connectors
- Never change the design of a circuit or 'band-aid" components. You are not the designer and the circuit worked fine before it failed so fix it properly.

Always be aware of your personal safety, and the safety of the customer. Even if you are repairing your Mum's TV you don't want to kill her or burn the house down due to your shoddy repair - know your limitations and seek professional help if needed.

Of course there are things I have forgotten to mention.

My final point is, you can fault find with just a Multimeter. It is the most useful piece of test equipment you will have, try and get yourself an old type Analogue Multimeter too. An oscilloscope is also helpful, it doesn't have to be a storage one as I still use my analogue scope of 20 years. I know Dave uses some of the equipment he has for educational value but honestly you don't need them, they are just "bling" and can confuse rather than clarify a problem.

If you read this Dave, keep up the good work. I do admire what you are doing.
« Last Edit: June 19, 2014, 02:07:54 am by What_NZ »
 

Offline Richard Crowley

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Re: Dave's fault finding technique and other stuff.............
« Reply #1 on: June 19, 2014, 02:17:00 am »
Hear! Hear! 
Maybe a proper series on the principles of (BrEnglish) fault-finding or (AmEnglish) troubleshooting would be a valuable thing to add to the schedule. It could be of benefit to both young players as well as old hands.  And even better if he could show how to do it without using $1000s worth of test equipment.
 

Offline JoeO

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Re: Dave's fault finding technique and other stuff.............
« Reply #2 on: June 19, 2014, 02:47:42 am »
Minor point What_NZ.

" ... the most useful piece of test equipment ..." is sitting on top of your shoulders.

The day Al Gore was born there were 7,000 polar bears on Earth.
Today, only 26,000 remain.
 

Offline What_NZ

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Re: Dave's fault finding technique and other stuff.............
« Reply #3 on: June 19, 2014, 02:52:21 am »
Minor point What_NZ.

" ... the most useful piece of test equipment ..." is sitting on top of your shoulders.

Oh so true......

 

Online edpalmer42

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Re: Dave's fault finding technique and other stuff.............
« Reply #4 on: June 19, 2014, 02:52:42 am »
Minor point What_NZ.

" ... the most useful piece of test equipment ..." is sitting on top of your shoulders.

I thought that was the least used piece of test equipment.

.......Been there.........Done that.......

Ed
 

Offline What_NZ

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Re: Dave's fault finding technique and other stuff.............
« Reply #5 on: June 19, 2014, 03:02:34 am »
Hear! Hear! 
Maybe a proper series on the principles of (BrEnglish) fault-finding or (AmEnglish) troubleshooting would be a valuable thing to add to the schedule. It could be of benefit to both young players as well as old hands.  And even better if he could show how to do it without using $1000s worth of test equipment.

Yes it would be good but judging Dave's previous repair video's he would need to get back to basic principles. In the 30 (and more) years of repairing just about every type of electronic consumer product Panasonic made, I have never needed to use a Thermal Imaging camera or an ESR meter.
 

Offline What_NZ

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Re: Dave's fault finding technique and other stuff.............
« Reply #6 on: June 19, 2014, 03:08:24 am »
Minor point What_NZ.

" ... the most useful piece of test equipment ..." is sitting on top of your shoulders.

I thought that was the least used piece of test equipment.

.......Been there.........Done that.......

Ed

Sometimes you would think that is also true. I had a Technician trust upon me for training that had been trained (from apprenticeship) by Philips, possibly one of the most illogical thinking tech's I have ever dealt with/(to) - hehe, yes I was a hard task master - lol
 

Online EEVblog

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Re: Dave's fault finding technique and other stuff.............
« Reply #7 on: June 19, 2014, 03:27:45 am »
Yes it would be good but judging Dave's previous repair video's he would need to get back to basic principles. In the 30 (and more) years of repairing just about every type of electronic consumer product Panasonic made, I have never needed to use a Thermal Imaging camera or an ESR meter.

The thermal imaging camera was just for kicks, because I could. I did not mean to imply this is what you should use.
And in-circuit ESR meters are incredibly popular in the TV/consumer repair industry.
 

Offline Mr Smiley

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Re: Dave's fault finding technique and other stuff.............
« Reply #8 on: June 19, 2014, 03:36:24 am »
I've always found Design Engineers to be really awful Repair Engineers. And Repair Engineers/Technicians exceptionally good at repairing and correcting bad designs.

 :)
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Online EEVblog

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Re: Dave's fault finding technique and other stuff.............
« Reply #9 on: June 19, 2014, 03:39:17 am »
1/ Confirm the customers description of the fault, also confirm the correct functionality of overall operation

I did.

Quote
2/ Check visually the outside for anything unusual or signs of damage, physical damage, liquid ingress etc

I did.

Quote
3/ Open the unit and recheck customers description of the fault, also reconfirm the correct functionality of overall operation

I did.

Quote
4/ Start a complete visual inspection looking for anything unusual, charring, over heating, damaged components, corrosion, obvious dry joints

I did. Dry joints are a bit hard without taking out the PSU board, so you do top side visuals first.

Quote
- Check for intermittents, tap test, flexing the PCB either by hand (safety first of course) or an insulated object.

I eventually got to that (and not as long into it as you think, things are done differently and slower because I'm shooting a video at the same time), but it was not my first step in this case because there was no indication that there was a mechanical aspect to this fault. It's not like my mum whacked the set and it came good etc.
The symptoms pointed toward an aging electrical fault. e.g. capacitors, marginal PSU or some such.
Any tech who repaired this TV without at least checking those caps (at least visually), then I would call them a bad tech.

Quote
- Alternating between a can of Freeze and a Hair dryer can help to isolate temperature related faults. Also helpful are small gas powered hot air blowers for pin point heating, even the hot tip of a soldering iron can be useful (be careful it is grounded)

I didn't get that far because the mechanical stress test was next in the list.

Quote
- Never assume that just because you have voltage you don't have excessive ripple.

That's why I used a scope.

Quote
- Before replacing a fuse (of any type) ask yourself "why did it fail?" check the resistance of the circuit on the secondary side.

I did. That was off camera, forgot to include it.

Quote
- Carefully unplug, check and reconnect all relevant connectors

Did that.

Quote
- Never change the design of a circuit or 'band-aid" components. You are not the designer and the circuit worked fine before it failed so fix it properly.

I didn't do that.

Quote
My final point is, you can fault find with just a Multimeter. It is the most useful piece of test equipment you will have, try and get yourself an old type Analogue Multimeter too. An oscilloscope is also helpful, it doesn't have to be a storage one as I still use my analogue scope of 20 years. I know Dave uses some of the equipment he has for educational value but honestly you don't need them, they are just "bling" and can confuse rather than clarify a problem.

Well, there's a shock, a multimeter and an oscilloscope are the two basic electronics troubleshooting tools, who would have thought!
I used both here of course.
A few people commented on the fact that I used an Agilent 3000X series scope for this. And of course that's just a pointless comment.

I honestly don't see how I did anything grossly wrong or out of place here?  :-//
The thermal camera was for kicks as I said.
I opened the case and checked the basics based on the symptoms I had to hand, and found and fixed the fault pretty quickly.
« Last Edit: June 19, 2014, 03:46:01 am by EEVblog »
 

Online EEVblog

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Re: Dave's fault finding technique and other stuff.............
« Reply #10 on: June 19, 2014, 03:43:41 am »
I've always found Design Engineers to be really awful Repair Engineers. And Repair Engineers/Technicians exceptionally good at repairing and correcting bad designs.

Well, yeah, of course. I haven't done professional general repair work since 1989/90, and have never repaired consumer items or TV's.
A professional TV tech probably could likely have told you the fault without even opening the case.
 

Offline sleemanj

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Re: Dave's fault finding technique and other stuff.............
« Reply #11 on: June 19, 2014, 03:45:16 am »
I have never needed to use a Thermal Imaging camera

30 years ago you wouldn't have had a hand held reasonably high resolution real time thermal imaging camera sitting on your desk.

Do we forsake new tools simply because "I never needed them before". 

Paper maps still work, so why do we have GPS?

~~~
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Offline What_NZ

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Re: Dave's fault finding technique and other stuff.............
« Reply #12 on: June 19, 2014, 03:57:19 am »
I have never needed to use a Thermal Imaging camera

30 years ago you wouldn't have had a hand held reasonably high resolution real time thermal imaging camera sitting on your desk.

Do we forsake new tools simply because "I never needed them before". 

Paper maps still work, so why do we have GPS?

Yikes!   I never said "30 years ago" maybe read before you post. You obviously missed the whole point. Ever heard of the saying "just because you can, doesn't mean you need to."
 

Offline Mr Smiley

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Re: Dave's fault finding technique and other stuff.............
« Reply #13 on: June 19, 2014, 04:02:24 am »
I have never needed to use a Thermal Imaging camera

30 years ago you wouldn't have had a hand held reasonably high resolution real time thermal imaging camera sitting on your desk.

Do we forsake new tools simply because "I never needed them before". 

Paper maps still work, so why do we have GPS?

Yikes!   I never said "30 years ago" maybe read before you post. You obviously missed the whole point. Ever heard of the saying "just because you can, doesn't mean you need to."

Yes you did, reply #5 :-DD
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Offline What_NZ

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Re: Dave's fault finding technique and other stuff.............
« Reply #14 on: June 19, 2014, 04:03:28 am »
Yes it would be good but judging Dave's previous repair video's he would need to get back to basic principles. In the 30 (and more) years of repairing just about every type of electronic consumer product Panasonic made, I have never needed to use a Thermal Imaging camera or an ESR meter.

The thermal imaging camera was just for kicks, because I could. I did not mean to imply this is what you should use.
And in-circuit ESR meters are incredibly popular in the TV/consumer repair industry.

Yes that's why I said in the first post
<SNIP>
I know Dave uses some of the equipment he has for educational value but honestly you don't need them, they are just "bling" and can confuse rather than clarify a problem. <SNIP>
Some workshops have ESR meters but good techs never need to use them, for instance we never had one at Panasonic.
 

Offline What_NZ

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Re: Dave's fault finding technique and other stuff.............
« Reply #15 on: June 19, 2014, 04:16:37 am »
I've always found Design Engineers to be really awful Repair Engineers. And Repair Engineers/Technicians exceptionally good at repairing and correcting bad designs.

<SNIP>
A professional TV tech probably could likely have told you the fault without even opening the case.

If he had it would have been a guess, you did the right thing by opening it up.
« Last Edit: June 19, 2014, 05:07:49 am by What_NZ »
 

Offline What_NZ

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Re: Dave's fault finding technique and other stuff.............
« Reply #16 on: June 19, 2014, 04:24:41 am »
<SNIP>
I honestly don't see how I did anything grossly wrong or out of place here?  :-//
The thermal camera was for kicks as I said.
I opened the case and checked the basics based on the symptoms I had to hand, and found and fixed the fault pretty quickly.

I am truly sorry if I have offended you, it was not my intention. The repair methodology was general and for everyone, it wasn't directed specifically at you or at that particular repair.
It was when you removed the caps to test with the ESR meter without checking voltages first and then the bodgy job with the connector at the end. It seemed like you ran out of time and said "Oh to hell with it" and the end repair was a big let down. Especially for a tech like me, I have never done that sort of thing in my life.
« Last Edit: June 19, 2014, 04:31:19 am by What_NZ »
 

Offline What_NZ

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Re: Dave's fault finding technique and other stuff.............
« Reply #17 on: June 19, 2014, 05:05:33 am »
I've always found Design Engineers to be really awful Repair Engineers. And Repair Engineers/Technicians exceptionally good at repairing and correcting bad designs.

 :)

Yes in general I would agree. Some designer's don't want to hear about their bad design but it is amazing how it gets corrected in a future revision. I worked with the team that designed the world's first Direct Drive electronically commutated washing machine. It was a great design but the lead designer had the communications lead from the control panel module coming down from the top of the machine and the motor harness going into a plug/socket on the top of the motor drive electronics module. I warned him that any moisture or condensation from a hot wash would collect on the wires and run down into the plug with obvious consequences. He didn't want to know about such a trivial thing and guess what happened after the product was eventually finalised and sold.... It only took a few months before we had trouble with corrosion in the connector. His solution was to make the wires longer so a drip 'U' could be put in and wrap some foam tape around the wires entering the plug.
 

Online EEVblog

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Re: Dave's fault finding technique and other stuff.............
« Reply #18 on: June 19, 2014, 05:19:14 am »
I am truly sorry if I have offended you, it was not my intention. The repair methodology was general and for everyone, it wasn't directed specifically at you or at that particular repair.
It was when you removed the caps to test with the ESR meter without checking voltages first

I was always going to test the capacitor ESR anyway, along with the voltages, so who cares which way around I measured them?
If that's your only complaint, then, well, nothing to see here.

BTW, there is a bit of "video production" involved here, I may not have necessarily done things the same way if I wasn't making a video.
I speculated on camera up-front that a likely culprit might be the capacitors, so it makes sense to check the capacitors visually and ESR first upon opening.

Quote
and then the bodgy job with the connector at the end. It seemed like you ran out of time and said "Oh to hell with it" and the end repair was a big let down.

I did run out of time. My mum wanted her TV back and I had an adequate fix, so that was that.
Those watching the live feed saw that. I literally fixed it and shot the last scene a minute before I headed out to pick up my mum.
What was I supposed to do, order a new TCON board and cable, and matching SMD fuse and wait a week or two before giving my mum her TV back and then uploading the perfect ending video?

Quote
Especially for a tech like me, I have never done that sort of thing in my life.

Because you are a professional repair tech being paid to fix things professionally for clients.
I am the complete opposite of that, fixing my mums TV in limited time for free. The result was adequate for the occasion IMO.
 

Online EEVblog

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Re: Dave's fault finding technique and other stuff.............
« Reply #19 on: June 19, 2014, 05:21:13 am »
If he had it would have been a guess, you did the right thing by opening it up.

Come on, any experienced person in this situation is going to have a guess up front.
If you, as professional repair tech claim you don't do that, then I'm going to call you liar  :P
 

Offline bitwelder

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Re: Dave's fault finding technique and other stuff.............
« Reply #20 on: June 19, 2014, 05:26:14 am »
Some workshops have ESR meters but good techs never need to use them, for instance we never had one at Panasonic.
I would hope that in a Panasonic product you don't have to hunt for shoddy one-hung-low capacitors  :o
 

Online ludzinc

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Re: Dave's fault finding technique and other stuff.............
« Reply #21 on: June 19, 2014, 05:34:56 am »
I've always found Design Engineers to be really awful Repair Engineers. And Repair Engineers/Technicians exceptionally good at repairing and correcting bad designs.

 :)

Yes in general I would agree. Some designer's don't want to hear about their bad design but it is amazing how it gets corrected in a future revision. I worked with the team that designed the world's first Direct Drive electronically commutated washing machine. It was a great design but the lead designer had the communications lead from the control panel module coming down from the top of the machine and the motor harness going into a plug/socket on the top of the motor drive electronics module. I warned him that any moisture or condensation from a hot wash would collect on the wires and run down into the plug with obvious consequences. He didn't want to know about such a trivial thing and guess what happened after the product was eventually finalised and sold.... It only took a few months before we had trouble with corrosion in the connector. His solution was to make the wires longer so a drip 'U' could be put in and wrap some foam tape around the wires entering the plug.

God, I hate when people play the 'I told you so' card.

You believed there was a problem with the design, you had one conversation with a stubborn twit, and then let the company deal with the consequences?

If you were so sure of your convictions why did you not pursue this further?

Not a great team player there...

In my career I've done tech, design and now management, and I've learnt a lot from everyone at each phase.  But its surprising how hard it is to get people to COMMUNICATE with each other.  Blame belongs on both sides there.
 

Offline What_NZ

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Re: Dave's fault finding technique and other stuff.............
« Reply #22 on: June 19, 2014, 05:35:12 am »
Some workshops have ESR meters but good techs never need to use them, for instance we never had one at Panasonic.
I would hope that in a Panasonic product you don't have to hunt for shoddy one-hung-low capacitors  :o

See my other Thread https://www.eevblog.com/forum/reviews/repair-3com-basline-switch-model-2808/ about failed Nichicon capacitors in a 3com network switch. A quality product with quality caps. The brand doesn't matter the frequency of failure will so it can happen.
I hope you don't think Panasonic only use Panasonic Capacitors?
 

Offline What_NZ

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Re: Dave's fault finding technique and other stuff.............
« Reply #23 on: June 19, 2014, 05:42:18 am »
I've always found Design Engineers to be really awful Repair Engineers. And Repair Engineers/Technicians exceptionally good at repairing and correcting bad designs.

 :)

Yes in general I would agree. Some designer's don't want to hear about their bad design but it is amazing how it gets corrected in a future revision. I worked with the team that designed the world's first Direct Drive electronically commutated washing machine. It was a great design but the lead designer had the communications lead from the control panel module coming down from the top of the machine and the motor harness going into a plug/socket on the top of the motor drive electronics module. I warned him that any moisture or condensation from a hot wash would collect on the wires and run down into the plug with obvious consequences. He didn't want to know about such a trivial thing and guess what happened after the product was eventually finalised and sold.... It only took a few months before we had trouble with corrosion in the connector. His solution was to make the wires longer so a drip 'U' could be put in and wrap some foam tape around the wires entering the plug.

God, I hate when people play the 'I told you so' card.

You believed there was a problem with the design, you had one conversation with a stubborn twit, and then let the company deal with the consequences?

If you were so sure of your convictions why did you not pursue this further?

Not a great team player there...

In my career I've done tech, design and now management, and I've learnt a lot from everyone at each phase.  But its surprising how hard it is to get people to COMMUNICATE with each other.  Blame belongs on both sides there.

He was the lead designer, I was the junior maybe you never worked in a large company before or maybe you are just different. My concern was heard and documented, I was overridden by the man in charge. Yes, there is no 'I" in "Team" I didn't want to be the no "U" in team either. I am not going to loose my job just for the sake of pride.
 

Offline What_NZ

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Re: Dave's fault finding technique and other stuff.............
« Reply #24 on: June 19, 2014, 06:01:05 am »
If he had it would have been a guess, you did the right thing by opening it up.

Come on, any experienced person in this situation is going to have a guess up front.
If you, as professional repair tech claim you don't do that, then I'm going to call you liar  :P

Wow that's a bit strong. Really you're going to call me a liar?
Your are not in the repair industry and haven't been since 1989/90 but profess to know "A professional TV tech probably could likely have told you the fault without even opening the case." All I said is, "it would have been a guess" anyone can guess of course but that doesn't mean they "know" and if he had said "It is the caps" he would have been wrong, as you found.
 


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