DIY TV repairs?

[presta]

he started poking and prodding inside it with a kitchen knife

If you're working on safe low voltage equipment you can sometimes learn quite a lot about what's going on by prodding around with a finger, or my tool of choice: a scalpel. Depending on whether it has an effect when it shouldn't, or no effect when it should, you can home in on where the problem is quite quickly. (But don't try it if you don't know what's safe and what isn't, obvs.)

 

[Alex321]

If you're working on safe low voltage equipment you can sometimes learn quite a lot about what's going on by prodding around with a finger, or my tool of choice: a scalpel. Depending on whether it has an effect when it shouldn't, or no effect when it should, you can home in on where the problem is quite quickly. (But don't try it if you don't know what's safe and what isn't, obvs.)

I'm not sure the insides of a CRT television really classed as "safe low voltage equipment"

 

[Regular.Cyclist]

I do the odd bit of home repair and have an ok amount of test gear. That includes a DVM, an oscilloscope (which I built myself), a bench power supply and a small thermal camera.

Problem I have found with a lot of low and mid end televisions is that the internals of two TVs with identical model names can be very different so buying another faulty unit as a possible parts donor often doesn’t work.

 

[Profpointy]

How do people find out these things in the first place?

Maybe someone with a decent understanding of the components things "what I need is a mild, non damaging, abbrasive. Mmm, wonder if a pencil rubber will work. I'll give it a try".

Whilst I can't now recall specifics, I'm sure I've gone through a few instances where I've
thought through the issue and wondering if such and such would work. Sometimes triumph, other times, well, it was busted already !

In a similar vein in the mobile phone world, after turning it off and on hasn't resolved an issue, the next thing to try is to rub the SIM contacts with a rubber

 

[CXRAndy]

Years ago back in the 80s my dad had a Philips CRT tv in his bachelor pad and it was making an awful crackling sound and flickering picture.
It had the old style fibre board type cover on the back with loads of thin slat type vents in it ,and you could see the wall behind the tv randomly light up with the silhouettes from the slated vents.Its was clearly shorting out somewhere.
My dad was a total nightmare / wally when it came to diy and he had no common sense or fear of electricity.
One night he got fed up with it and decided to try and fix it..
Most normally sane people would switch the TV off and unplug it before taking it apart but not my dad.
Armed with just a few kitchen knives he took the fibre board back off ,with the telly still on because in his words"he wanted to listen to the news"
With the back off the tv he started poking and prodding inside it with a kitchen knife and asking me if there was any improvement in the picture.
I was sat on the sofa horrified waiting for him to blow himself up , and then all of a sudden the picture stopped flickering and the cracking noise disappeared.
He emerged from the back of the tv looking rather please with himself.
It turned out the braided earth strap on the back of tube had come loose and he somehow managed to tightened it up with a kitchen knife to sorted it out.
To this day I don't know how he never got electrocuted.
How he's managed to get to the ripe old age of 80 is a miracle 🤣

The lecturer at college used to say the CRT television was the perfect piece of equipment to work on for learning.

Rf tuner circuits

It incorporated signal circuits both AM and FM modulation, from audio range to video.

Power amplifiers in push pull and standard drive for audio and video and frame, line scanning

Inductive circuits for frame, line, correction

Power supplies both mains, low voltage, right upto to 37kVolt EHT tube drive for focus and final acceleration of beam.

Digital circuits for control, teletext, and storage.

If you could fix all of these you were OK at your job.

Like most repairs, common faults were know, bread and butter earning. The fun was you got an unusual fault where the manuals had to come out, fault finding, down to component level.

 

[CXRAndy]

If you're working on safe low voltage equipment you can sometimes learn quite a lot about what's going on by prodding around with a finger, or my tool of choice: a scalpel. Depending on whether it has an effect when it shouldn't, or no effect when it should, you can home in on where the problem is quite quickly. (But don't try it if you don't know what's safe and what isn't, obvs.)

Try that with a microwave.

I used to test the magnatron in a live configuration with an old AVO meter. The only one back in the day that could cope with just short of 3kV Voltage reading. Fluke meters were around 1.5kV

You could ascertain quite a bit from the current being drawn by the magnatron an d where the problem was.

Modern technicians swap a part, check it works. Then swap another if it doesn't.

 

[Shearwater Missile]

Try that with a microwave.

I used to test the magnatron in a live configuration with an old AVO meter. The only one back in the day that could cope with just short of 3kV Voltage reading. Fluke meters were around 1.5kV

You could ascertain quite a bit from the current being drawn by the magnatron an d where the problem was.

Modern technicians swap a part, check it works. Then swap another if it doesn't.

When I was an engineer working on MWO`s we had a probe meter to test the voltage, all well in theory. The only problem was that at the base of the handle which you held it with, there was a socket with exposed metal. As I was checking the voltage my hand must have been in contact with the socket as I took full force of 3kv. It shot me across the room I can tell you. I never used that meter again. It was a wonder I survived !

 

[Regular.Cyclist]

The lecturer at college used to say the CRT television was the perfect piece of equipment to work on for learning.

Rf tuner circuits

It incorporated signal circuits both AM and FM modulation, from audio range to video.

Power amplifiers in push pull and standard drive for audio and video and frame, line scanning

Inductive circuits for frame, line, correction

Power supplies both mains, low voltage, right upto to 37kVolt EHT tube drive for focus and final acceleration of beam.

Digital circuits for control, teletext, and storage.

If you could fix all of these you were OK at your job.

Like most repairs, common faults were know, bread and butter earning. The fun was you got an unusual fault where the manuals had to come out, fault finding, down to component level.

A lot of people in my line of work were originally tv repairers before joining the NHS. No longer happens since CRTs fell out of fashion.

 

[Shearwater Missile]

A lot of people in my line of work were originally tv repairers before joining the NHS. No longer happens since CRTs fell out of fashion.

I was told when I started my apprenticeship in tv repairs to keep one hand in your pocket and use the other to work with. It`s a pity I did`nt do that with the microwave test meter.