No Power In Philips CRT TV Repaired
The complaint of this 21″ Philips CRT TV was no power. The first thing to do is to remove the cover and check the circuit board especially the fuse.
Before I check the fuse I cleaned up the circuit board first that was full of dirt and dust.
After cleaning up the circuit board I took out my digital multimeter and set to buzzer range and measured the main fuse. It was opened circuit because there was no reading registered in my multimeter.
I did not stop there as I proceeded to check on the corresponding components especially the 4 bridge diodes. I found two of the 4 diodes were shorted and this is the cause why the main fuse was opened circuit.
If one or two bride diodes were shorted the best is to replace all the other diodes. If you replace only the two faulty diodes, the other two diodes will get shorted later. I order to prevent repeat call from the customer, direct replace the 4 diodes even if you found only one shorted.
I did not connect the fuse after the replacement of the 4 diodes because I want to connect a 40 watt bulb to check if there is any other short circuit in the board.
The bulb lighted up for a while and then went off which indicates there is no longer short circuit in the circuit board and I can connect back the main fuse and power On the TV. The TV infact was working fine once the power was switched On-see the photo below:
This article was prepared for you by Suranga Bandara who owns an Electronics shop in Anuradapura, Sri Lanka.
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Note: You may check out his previous repair article in the below link:
https://www.jestineyong.com/no-sound-in-3-channel-subwoofer-system/
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Albert van Bemmelen
September 28, 2015 at 6:03 pm
Thank you Mr.Suranga. What could be the reason for the power bridge diodes to have failed? Could it be an over-Voltage in the AC Line? Or is that something that doesn't happen in Sri-lanka? Or is the cause maybe the so called Father/Mother effect that occurs when Father switches on the TV-set, and Mother directly after that switches it off again. And Father switches it on again etcetera. When the TV already was warmed up and the input current rises because of the lower Demagnetizing Coil circuit resistance? Or is it just some inferior Diodes? In my country this mostly happens after lightning strikes on the Power Line or when someone accidentally gives the TV water (like my Brothers wife did when watering a plant on the TV - LOL).
Chris
September 29, 2015 at 4:05 pm
It's cool! I like this FM effect. I never heard this saying Father/Mother effect. 🙂
In most case this can be the problem.
But who will bring the equipment to repair than? Father or Mother? 🙂
I like this FM saying.
Albert van Bemmelen
September 29, 2015 at 10:40 pm
Hi Chris, I guess it has to do with the PTC or NTC effect of components inside the TV.
And why an old light Bulb mostly breaks down when it is cold and it is switched on (PTC).
That Father/Mother effect is something that I must have read somewhere in the past and remembered. Maybe it was in the Television Engineering Course I've completed in the past as one of many Courses I did? I can't tell you.
Humberto
September 29, 2015 at 11:24 pm
Wow! Albert, here in my country the Father/Mother effect is different (one TV set per house most of the times): Father wants to see the Baseball game and Mother wants to see the soap opera broadcasted at that moment (remember, different channels baseball game and soap opera), and therefore the channels are being changed all the time, and most of the times it finishes in a quarrel: LOL anyone who is outer looking at this show.
s ramachandran
September 28, 2015 at 6:15 pm
Mr suranga..
Thanks for yr post ... I am enjoying ur all the repair tipps posted in this blog .. I appreciate your great work . God bless you
Yogesh Panchal
September 28, 2015 at 9:26 pm
suranga. Nice fix with professional approach.
john
September 28, 2015 at 11:16 pm
what might be the problem in a 21 inch crt monitor when picture flicker continuously?
randy
September 29, 2015 at 1:07 am
A nice and proper repair, it is very important to replace any parts that may have been stressed by the failure of the other parts, such as the other 2 diodes in the bridge, not many techs seem to realize this factor of stress in their repairs. The primary cost in repairs is time, and opening/disassembly-closing/assembly is usually half the time in a job, so proper techniques and understanding help to prevent call-backs.
Andrew F. Ali
September 29, 2015 at 4:03 am
Please check the Horizontal Output Transistor and the Large Filter Capacitor as an additional precaution next time. Great job......Regards.
Chris
September 29, 2015 at 4:09 pm
Nice and clean explanation.
Congratulation for the repairing.
My best regards.
Humberto
September 29, 2015 at 11:07 pm
Good repair Suranga, congratulations.
aziz
September 30, 2015 at 4:57 am
Thank you very much
Mahmoud
September 30, 2015 at 6:47 pm
nice work good
Congratulation for the repairing.
My best regards.
Ulises Aguilar Pazzani
October 3, 2015 at 11:45 am
grat job Mr Bandara
Paris Azis
October 8, 2015 at 6:26 pm
Good job Suranga!
Amir Mukhtar
October 13, 2015 at 3:39 am
Mr. Suranga
Thanks you for Another good article
keep sharing
thanks you
Amir Mukhtar Ashrafi
Karachi. Pk.
mhandu
August 26, 2018 at 8:55 am
Thank you very much soon I will become an expert like you
Andy
August 26, 2018 at 12:47 pm
This is awesome thanx