I was visiting a client, who wanted her television checked by a technician; she has left a message to her neighbor who has a shop on the same block to direct me to her house.
Once I reached the shop, I introduced myself and my
mission there, while talking to the lady another client of mine whom I have
repaired his television previously passed
by and as we greeted each he mentioned that I really helped him to revive his
dead television.
The shop owner heard the conversation and was interested
to see if I can revive her television which was hit by power surge and decided
to keep it in the store.
I proceeded to my mission and while coming back I found the
lady has already picked the television from the store waiting for me.
I opened the television and since it was hit by power
surge I was much interested on the power supply which always super heavy
casualties once hit by power surge.
First I checked the state of the main capacitor and found
its top part lightly swollen.
With this I concluded indeed this was power surge, sorry I
did not take a photo before removal from the board.
I tested the bridge diode using my digital meter and
found its okay, after changing these two components I decided to apply the
power using the series current
limiter and noted the bulb was shinning like the sun even after one minute, with this I concluded there is a
still a shorted(s) component on the power supply.
I tested the voltage across the bridge diode middle pins
(ac pins) and found the voltage was quite low.
I decided to replace the diode bridge directly and see if
it was failing under load since I had already tested it using the meter and
tested good.
After replacing the bridge diode I noted the voltage is
now normal and the voltage on the secondary side was also present, the B+
voltage was also present and stable, but the TV could not fire, No High voltage.
The power on Led was also blinking and this leads me to conclude
I am not out of the wood.
I pulled my ESR meter and begin testing the secondary
output filter capacitors starting with the lines which I noted the voltage was dancing
a lot for lack of better word.
I bumped on capacitor C945 rated 1000uF/25 volts which in
circuit ESR reading was around 3 ohms, I decided to remove it out of circuit
and test again using multi-components tester and this is what I got.
ESR of 14 ohms and capacitance has dropped by half not forgetting the V-losses.
I replaced this capacitor and again tested the effects of
that and I was happy with what I saw.
The TV is now up and running
Thank you guys
See you on the next class
Online classes on basic electronic course going on here.
Great article,how much is the esr meter in Kenya.
ReplyDeleteHi Brian, Not in Kenya market. You can buy from Aliexpress.
DeleteRegards Humphrey
Good read for refreshing the logical steps in crt tv repair. Am also interested in multicomponent tester as mine stopped working. I like component level repair rather than replacing a whole board which are expensive and not readily available in our market. Have also learned that most people who sell spare parts are clue less about their wares. Some don't even know the parts they have in stocks.
ReplyDelete