Is it necessary to power on in order to diagnose failure IC of CRT TV?

[bshi02]

I finally measured voltage of STR-W6754 with switching on.(I placed black probe to negative pin of big capacitor(main filter capacitor) and placed red probe to #pin 4 of STR-W6754.)
It was measured DCV 10.2
So I browsed through STR-W6754 datasheet, and found below information.

Standby Non-Operation Circuit Current: Icc(s) Vcc=10.2V Vfb=1.6V
FB Terminal Inflow Current,Standby Operation Ifb(s): Vcc=10.2V Vfb=1.6V

I think that something prevent STR-W6754 from got into "Standby Operation Start Voltage(15V)",So It always remained "Standby Non-Operaiton Voltage(10.2V).
Is there any method to check components which affects
Standby Voltage" of Switching regulator in HOT area?

 

[bshi02]

I tested Horizontal output transistor with LCR-t4 meter which has been desoldered from pcb of CRT TV and It was written "C6090" on its surface.

But Whenever I test this HOT with lcr-t4 meter, it always displayed capacitor result instead of NPN transistor.

I tested spare AOD412 MOSFET with LCR-t4 meter and It displayed correct result.

And I followed below guide which shows how to test Horizontal transistor with analouge meter.

I found that when I placed red probe to # pin2(collector) and placed black probe to pin3(emitter), Indicating needle won't move at all in x10 ohm mode.
Is this HOT IC(C6090) defective and Should I purchase it in order to fix symptom of staying in Standby Non-Operaiton?

 

[poormystic]

Hello.

A few days ago,I stumbled on A slimCRT TV(21fu1r-ns of 220 voltage) in a recycling bin.

But,Unfortunately It is impossible to power on this slimCRT TV.

So I dismentled this slimCRT TV,and found that its fuse never have been blown and Voltage of big capacitor(main filter capacitor) is 315v

But I have little experience and knowledge about electronics repair,So I searched for any information about repairing "Not turning on CRT TV"

I found that it is necessary measuring voltage of drain and source pin in STR power regulator or measuring voltage of diode anode and cathode with power on.

But I really really dread that If I power on PCB of this slimCRT TV and If there is something wrong with measuring method of digital multimeter,It would cause burst of cathode-ray tube or catching fire or electric-shock accident..

So I want to measure any doubtful diode or power regulator or any IC with power off.

Is it really necessary to power on this slimCRT TV in order to diagnose failure IC of this slim CRT TV?

I like others here especially the moderators, have undergone extensive professional training in electronics repairs
If my first day apprentice were to go near the circuit you're trying to fix I would think him very likely to die. I would absolutely stop him from doing any such thing and I now advise you the same.
I'm in my late 60s and I've seen a lot of **** go down so take notice!
With smiles but, and do find some safe stuff to get started on

 

[bshi02]

I know that It is really dangerous for novice to measure voltage on the soldering point of CRT TV with switching on.
So Before measuring CRT TV's voltage with switching on or discharging anode cap, I ALWAYS put on a leather and plastic or cotton gloves in layers,and I even made an analogue meter probe with crocodile clip like below screenshot and So I clip it to the negative pin of the main Capacitor or turner gound and take voltage measurement using one hand, So It give no chance any current in CRT TV to pass through my body.

 

[ramussons]

Hello.

A few days ago,I stumbled on A slimCRT TV(21fu1r-ns of 220 voltage) in a recycling bin.

But,Unfortunately It is impossible to power on this slimCRT TV.

So I dismentled this slimCRT TV,and found that its fuse never have been blown and Voltage of big capacitor(main filter capacitor) is 315v

But I have little experience and knowledge about electronics repair,So I searched for any information about repairing "Not turning on CRT TV"

I found that it is necessary measuring voltage of drain and source pin in STR power regulator or measuring voltage of diode anode and cathode with power on.

But I really really dread that If I power on PCB of this slimCRT TV and If there is something wrong with measuring method of digital multimeter,It would cause burst of cathode-ray tube or catching fire or electric-shock accident..

So I want to measure any doubtful diode or power regulator or any IC with power off.

Is it really necessary to power on this slimCRT TV in order to diagnose failure IC of this slim CRT TV?

You will be taking a lot of risks, mainly because you are new to this.
CRT's handle about 10 Kilo Volts on its screen!. The capacitors can retain charge for quite some time - maybe days. And you cannot troubleshoot without switching ON.

 

[poormystic]

And if you succeed in this venture I fear you'll think you're now ready to tackle a microwave - thinking that's only 5kV so you must now be ok with that, after your 10kV experience.
It's not just novices who are at risk

 

[Delta Prime]

with that, after your 10kV experience.
It's not just novices who are at ris

This has been covered already the gentleman is competent understanding of the risks involved and have taken the proper precautions he has done his own research and is looking for confirmation.

 

[Delta Prime]

The capacitors can retain charge for quite some time - maybe days.

Same as above.
Resources are limited in South Korea....

https://maker.pro/forums/threads/is-it-necessary-to-power-on-in-order-to-diagnose-failure-ic-of-crt-tv.300307/post-1853802

 

[bshi02]

By refering to below tutorial,I tried to repair another 29 inch CRT TV(LG CN 29H3) which i sometimes have used for playing retro game console and It suddenly broke down a week ago.
I measured voltage of power regulator ic(STR-S6707) with switching on, which is a crucial component of CRT TV's PCB in HOT area.
https://www.electronicsrepairmadeas...er-supply-problems-smps.html?lr=1715042500018
I successfully measured voltage pin#1(collector 370-400DCV)#9(vccin 6.2-6.6DCV) of STR-S6707 with analogue meter.
But I noticed that when I measured voltage between the biggest capacitor(main filter capacitor),It was 300-320DCV,But when I measured voltage of pin#1 of STR-S6707 It was 370-400DCV.
In order to raise the accuracy of voltage measurement, So I tried to measure it with hioki CARD HiTESTER 3240 which my father ,who has already passed away, bought me more than 30 years ago.

To my surprise,As soon as I placed hioki CARD HiTESTER 3240's black and red probe to negative pin of the biggest capacitor and pin#1 of STR-S6707,I saw big sparks from soldering point of STR-S6707(pin#1)

This big spark cause to peel off some of upper soldering pad(pin#1 of STR-S6707) like below screenshot.

It is screenshot After I finished to desolder STR-S6707..

And I doubt that this big spark would spoiled component(FB802,FB804) which is very close to pin#1 of STR-S6707.
I think that If I connect this PCB of CRT TV to cathode ray tube and switch on, There would be a possibility to malfunction or even catch a fire as high voltage(370-400DCV) pass through this damaged soldering pad(pin#1 of STR-S6707).
Should I throw away CRT TV's PCB which has damaged soldering pad of power regulator ic(pin#1 of STR-S6707)?
Or Although some of soldering pad(pin#1 of STR-S6707) have been damaged ,where high voltage(370-400DCV) pass through, Is it safe to mount STR-S6707 power regulator by soldering and continue to test it?