I received a phone call from my neighbor who wanted his
television checked by a technician, I passed by his place and picked the
I went back to the shop and after applying power via my
series current limiter bulb I noted the Television has no sigh of life.
But listening carefully I could hear some chi-chi sound
coming from I can’t tell exactly where. I opened the television and tested
across the man capacitor and I get around 300 vdc which is not bad for those
using 240 Vac.
I tested across all the secondary outputs and I got less
near zero volts on all outlets, I decided to switch the power off and do some
resistance testing across all the secondary outputs, this was done across the
secondary diodes and I noted one line was dead short.
Upon close investigation I noted it was the B+
line and therefore decided to check the health of the HOT transistor and to my
surprise it was dead short.
For those who have been doing CRT television you will agree
with me that rarely does HOT transistor short without a cause.
So do not be quick to replace HOT transistor when found
shorted otherwise chances are high to get shorted again after sometimes or
This problem of H.O.T getting shorted
immediately or after some times of replacement has given many technicians sleepless
that I decided to include a whole chapter in my book CRT television repair course on how to solve this problem seamlessly
replacing the HOT transistor, I decided to do some detective work and I was not
happy with the diode shown below.
Kindly note that the photo was taken after replacing the diode with another I got
from the junk but both were FR(fast recovery) diode otherwise if you use
ordinary diode it will burn instantly.
This diode(D435) has one leg connected to the collector of
After replacing these two components I decided to power up
and see the effect and this is what I saw.
The television is now up and I run it for two hours nonstop
and still no issue detected.
Check out my latest book on foundations
in electricity and electronics NOW selling at my Amazon store, Hard
copy(paperback) now available.
Online classes on basic electronics going on!
Thanks for sharing. Tho am wondering why you didn't replace the transistor driving HOT to avoid call back.ReplyDelete
Not always Sylvester.Delete
Very good, Humphfrey. Quick and efficient. Thanks for sharing.ReplyDelete
Henrique J. G. Ulbrich
Thank you and welcome my friend. J.GDelete
GREAT JOB SIR
Thanks, am humbled by your remark.Delete
gracias por compartir tus conocimientos-muy interezante,gracias.saludos desde Colombia.ReplyDelete
Gracias mi amigaDelete
Hello there. CRT TV is not used much in our country. You fixed it very well. Greetings from Turkey...ReplyDelete
Hi mr. HumphreyReplyDelete
I have a 28 inch grundic tv.
Tv has sound but no picture , as if tv is off but sound come out of speakers.
Heater not glowing , and there is not high voltage in anode cap, i can not see spark in anode cap.
I am from iran , unfortunately in iran there is no repair guy to fix my tv , everywhere i go, they tell me this tv is not repairable, someone told me may be flyback transformer is the problem.
Mr. Humphrey please guide me how i can troubleshoot the problem , i dont have money to buy a new tv. in iran everything is so expensive due to sanctions from usa.
Please help me to fix the tv.