Hazardous thing happened at work

[BGAmodz]

I am bad with Digital...even my Meter is Analogue like me

All the best,
tv

I also use analog meters , specially for diode/transistors tests.

 

[fezder]

I also use analog meters , specially for diode/transistors tests.

care to tell WHY specially?

 

[tvtech]

care to tell WHY specially?

Hi Fez

An Analogue meter loads the Junction under test with a little Current (Milliamps) when on the X1 range when checking Forward Biasing. This tends to show up a Junction going faulty or indeed faulty under a little load.

Analogue can reveal these suspect Junctions where a Digital declares them OK.

I have a packet that I have collected these Digital foolers in over the Years. All Junctions test fine on a Digital but fail with an Analogue. And all of these solved my problem with a repair.

Regards,
tv

 

[Nigel Goodwin]

care to tell WHY specially?

I'm with TVTech - analogue meters are still VERY useful.

 

[cowboybob]

I'm with TVTech - analogue meters are still VERY useful.

Especially if your looking for a very short (single digit ms) voltage/current/whatever spike/dip (and can't find your 'scope).

 

[tvtech]

Especially if your looking for a very short (single digit ms) voltage/current/whatever spike/dip (and can't find your 'scope).

Hi Bob

For me it's really the whole package. Running numbers on a Digital don't tell me all that is happening when a set is "tripping" for example.
An Analogue does. Pointer is showing me that it is twitching as it displays stuff. I can then fathom things out.

Old school I guess. But you know what in my experience Analogue meters never lie when repairing stuff.

Sure, the CRT game here. Others might disagree. Anyway, that is the way I do stuff. And it has worked for me

Regards,
tv

 

[fezder]

hey guys, thanks a lot for info! yet again learned something new! luckily i do have couple analogue meters, probably in working condition, i have kept them mostly as decoration....

 

[Nigel Goodwin]

An interesting fact with digital meters (at least in my experience) is testing LOPT stages in TV's - it's fed with around 100V to 150V DC, but has a 1000V flyback pulse on it when it working correctly. Using a digital meter (on the 1000V range) reads the correct DC voltage, but also lights up ALL the decimal points in the display - if there's no decimal points, then the LOPT isn't running.

 

[BGAmodz]

An interesting fact with digital meters (at least in my experience) is testing LOPT stages in TV's - it's fed with around 100V to 150V DC, but has a 1000V flyback pulse on it when it working correctly. Using a digital meter (on the 1000V range) reads the correct DC voltage, but also lights up ALL the decimal points in the display - if there's no decimal points, then the LOPT isn't running.

Nice info nigel .

But i thought a ring tester also known as RINGER was necessary for LOPT or other SMPS transformer.

I mean can a analog meter be used for other SMPS transformer types ?

Here is a schematic for a commercial ringer btw.

 

[Nigel Goodwin]

Nice info nigel .

But i thought a ring tester also known as RINGER was necessary for LOPT or other SMPS transformer.

Even better, but a digital meter gives more info than you think - showing if it's running or not.

Normally if the LOPTX has shorted turns it blows the LOPT - that's where the ringer comes in (I threw mine away a few years back - no call for them now ).

 

[tvtech]

Even better, but a digital meter gives more info than you think - showing if it's running or not.

Normally if the LOPTX has shorted turns it blows the LOPT - that's where the ringer comes in (I threw mine away a few years back - no call for them now ).

Lol....never used a ringer. I remember in the early 90's someone tried to sell us something like that.....tests for shorted windings and all...problem is that it does not test at actual working Voltage and stuff when things are oscillating...big difference.

My 2c. No offense Nigel. I am set in my ways and that is what I chirp about.
I always talk about what has worked for "me". As Mickey Mouse as I am

Regards,
tv

 

[Nigel Goodwin]

Lol....never used a ringer. I remember in the early 90's someone tried to sell us something like that.....tests for shorted windings and all...problem is that it does not test at actual working Voltage and stuff when things are oscillating...big difference.

It doesn't need to test at working voltages, a shorted turn is a shorted turn - and that's what it's testing for.

A forerunner of the LED and logic chips versions was using an old oscilloscope - some of those had a timebase output, and you could apply that to the LOPTX (a pulse to make it ring) and checks the ringing on the scope trace.

But neither the scope or LED version is foolproof - you need to have enough experience with different makes and models to know how they 'should' behave under a ringing test. The tester I used (which I built from a kit) had green LED's at the top (for good), red LED's at the bottom (for bad), and a fairly wide range of yellow in the middle (for - not really sure) But a few years of experience with it soon showed you what readings are good or bad on different sets.

A classic example would be a set 'clicking' (continually powering up and shutting down) - stick the tester on chassis and the collector of the LOPT, and press the button - an instant indication (with near zero effort) of the state of the LOPTX (which was a VERY common cause of such symptoms).

 

[tvtech]

It doesn't need to test at working voltages, a shorted turn is a shorted turn - and that's what it's testing for.

A forerunner of the LED and logic chips versions was using an old oscilloscope - some of those had a timebase output, and you could apply that to the LOPTX (a pulse to make it ring) and checks the ringing on the scope trace.

But neither the scope or LED version is foolproof - you need to have enough experience with different makes and models to know how they 'should' behave under a ringing test. The tester I used (which I built from a kit) had green LED's at the top (for good), red LED's at the bottom (for bad), and a fairly wide range of yellow in the middle (for - not really sure) But a few years of experience with it soon showed you what readings are good or bad on different sets.

A classic example would be a set 'clicking' (continually powering up and shutting down) - stick the tester on chassis and the collector of the LOPT, and press the button - an instant indication (with near zero effort) of the state of the LOPTX (which was a VERY common cause of such symptoms).

Hi Nigel

I love you Teddy Bear. Crazy how we are all taught differently. I toss stuff that never worked for me....

I will never forget the very first day I started working at Early Bird in South Africa. Employed as a Driver...only that. But I came armed with a Fluke 75.
Impressive...for a driver that can actually understand stuff..

My Manager shows me a Sony 191...tells me to test one of the frame output Transistors he has found faulty on the set...(we are talking Frame here and not dead). Easy peasy.

Take it, test it, and proudly proclaim the Fluke says all is good,

He says OK. Takes out his cheap little Analogue Chinese Meter and does a simple test with a little load on the Junction on test...says something like this:

"You see it is hanging there."...shows me....I still did not get it.

Frustrated he says "I will show you now". Takes my Fluke approved and tested Transistor back in the Frame Stage....still frame collapse.
Finds an older working and tested Transistor from a scrap Chassis and says "watch this".

Working. Full picture and all. I will never ever forget that lesson.

And I am sure that Nigel remembers the 191. We learned to do the mods and all and kept them going until guns were not available anymore.
Regunning of Tubes became a problem around 2000?

Lots of history here

Regards,
tv

 

[tvtech]

Now I feel terrible again. And with that comes Arnie.

Everyone has bailed. I am talking to myself. Again.

I still love you all. And with that Arnie comes to my rescue.

EDIT: Nah. Not changing Avatars tonight. Lately Arnie is all talk and no oomph.
Like a Girl without a Mission.

Regards,
tv

 

[JimB]

Calm yourself TV, don't feel too bad, the rest of the western world has other things to do now and again.

Meters, analogue v digital.
For may years I preferred an analogue meter (moving coil) for testing transistors and diodes, even if I was using a digital meter for general purpose fault finding.
Eventually I got to the stage in my day job where a digital meter was the only thing available, and finally I had a post where I no longer needed to test components from one month to the next.
In my home workshop my ageing analogue meter was becoming very unreliable, if I remember correctly it was the range switch that was the problem. I knew that it was time for it to go into the bin. I also knew that if I just put it into the bin, the next day Captain Paranoia would whisper in my ear "it is not that bad, take it back out of the bin", so I hit it with something big and heavy to render it beyond use.
Since that day I have not had an analogue meter on hand in my electronics work area.
I still have two analogue meters but they are in the garage, my "mechanical workshop".

TV tells us about transistors which tested OK but would not work in their intended application, in his case TV frame drive.
I have come across this problem about twice in roughly 50 years, but in my case it was always small signal transistors.
Tracing a signal through a circuit, it would dissapear after a certain stage.
Take the transistor out and test it, and it was ok on the "two diode" test with the meter, but it had no gain. An apparently working transistor but with no gain. Weird stuff.

Oscilloscopes, analogue v digital.
My main "go to" scope for general purpose work is a modern digital scope, made by Agilent, nice hand size to fit on the shelf above the workbench.
However, if I want to display the envelope of a high frequency waveform, such as a an amplitude modulated RF signal, the 30+ year old analogue scope beats it easily.
Maybe I have not got the right technique, or maybe Mrs Nyquists' little boy has a lot to answer for!

JimB