Sunday, November 13, 2016

21 Inch CRT Television dead now repaired

First let me point out this television belong to my youngest sister, she called me to pass by her place but due my busy schedule I was not able  to make in time.

Therefore she decided to ask for assistance from the nearest technician near her home town.

Of course this I came to learn later otherwise according to her the television never left the house.

I passed by her place and after a small briefing about how the problem started, I was told that there was power brown out in the estate when the problem started.

For those who don’t know what is power brownout- electrically speaking is a drop in voltage in an electrical power supply,so named because it typically causes lights to dim.

Most branded TVs have no problem with brownout but china made tvs have challenges when it come to brownout and therefore if you see lights are dim and you have china made tv it is advisable to shut it down and don’t try to use it as light source in your house otherwise you may end up paying more in repairs.

So I opened the television and since it was dead i started by checking the fuse and I found it open.

Next I checked the switching transistor and I found it open, after that I took the motherboard to my workshop for further testing since I was not intending to do any repairs on site.

After reaching my workbench I pulled the switching transistor out of circuit ready for replacement and after pulling it out I checked the part number and I was a bit skeptical about the part number of this transistor which was BU2523AF.

So I decided to google this transistor datasheet for the specification and this is what I got.

Looking at the general description my jaw almost dropped New generation, high-voltage, high-speed switching npn transistor in a plastic full-pack envelope intended for use in horizontal deflection circuits of HDTV receivers and pc monitors”

With this I concluded this tv was taken to another technician most likely the time I delayed to pass by her place but she didn’t like me to know although to me this was not a big deal.

As you can see this transistor is supposed to be used in horizontal deflection and therefore the technician missed the point big time.

So I pulled transistor D1710C and replaced this transistor and also the Main capacitor which I was not happy with plus the fuse.

Other components tested okay and therefore it was time to test the effect of the two components I replaced.

So I connected the board to the power supply using the series bulb trick and the bulb was bright at first and then dim and with that I confirmed there was no short in the supply.

As if that was not enough I also hear the HV fire and with that I concluded the tv is now working.

Note: It is very important to be extra careful with equipment from other technician and whenever you have any doubt about any component which was replaced previously it is always important to confirm by googling the datasheet of the component in question.

Later I went back to the sister place and re-installed the board back to the tube and after applying power the tv came back to life.

Thanks you guys

Talk soon!

1 comment:

  1. dear sir
    could u plz upload a screenshot
    how to
    connecte the board to the power supply using the series bulb ?
    both in the primary & secondary
    thank you