I got a phone call from a
customer who wanted his television checked and the complaint was picture is
okay but no audio.
I requested him to bring it
to the shop for checking and indeed he brought it up, i applied the power to
confirm what he said about the tv initial symptoms and yes he was correct and
therefore confirmed the television has audio problem.
I opened the set and went straight to the audio circuit and after scanning around the circuit for any suspect component, I found non.
Now it is time to use my ESR
meter to check capacitors around this circuit and again I never got any
capacitor which was suspect.
The next step is to check the
two speakers which were rated 10 Watts and 8 ohm impedance and therefore with
my digital meter set to diode range I tested across the speaker connector and
got open circuit.
I continued increasing the
range until I got open even on 10 Mega Ohm range and I concluded the speaker was
open.
I moved to the other speaker
and the reading were the same” open circuit”
With that I decided to find
out if the Audio i.c was working or not, to do this I have to do some preliminary tests and the most important to start with is to find out if the i.c is getting
stable and correct voltages.
To help me with the expected
voltages I had to google this model which I got easily and here is the circuit
diagram of IC LA42102L here below.
All the voltages were within range and this lead me to
conclude the I.C was suspect, also touching the i.c I found it was cold which
strengthened my case of suspecting it.
I went to the shop and bought a new one and after
replacement I tested with a small speaker around my workshop attached to the
previous speaker connectors and this time got audio and I was a happy man.
Before going into celebrating mode I remembered I have no
speaker of the type used in this television and also they are not in the
market.
To take care of this I decided to salvage one from a JVC
television junk lying around and did a replacement and the audio was good and
clean.
Thank you guys
See you in the next class
hi how about led tv repairs.
ReplyDeleteComing soon Khan!
DeleteRegards Humphrey
Thank you for sharing..
ReplyDeleteThanks and welcome my friend.
DeleteRegards Humphrey
I always enjoy your approach to troubleshooting. Thank You for Sharing!
ReplyDeleteThank you Morakinyo for your feedback. Appreciated.
DeleteRegards Humphrey
Hi sir please help me with my crt tv nippon japan no video only. 32 volts is presesnt on tuner and we also replaced tuner and memory 24c08 but still no reception. Tnx and god bless.don
ReplyDeleteCheck the RGB circuit at the CRT neck board, Seems like you are guessing what to change or not..i strongly advice you to invest in my eBook on CRT tv Repair course and don't forget to thank me later.
DeleteRegards Humphrey
Regards
First thanks again sir humphrey for sharing your repair articles regularly.I have a question on your method of diagnosing the trouble on that tv with no audio.when ypu check the speaker with your digital meter you set it in diode mode why can you not use in ohm setting?One more question sir, when you test the board by using the series bulb connecting to the B+ line is it possible to disconnect all wires leading to the picture tube so with the flyback disconnected to the picture tube as well.Because I read some of your previous articles that when you are in the costumer's house you bring home the board only to test it at home with the series bulb method leaving the picture tube and the TV casing. hope to have your reply soon.
ReplyDeleteHi Romeo, 1.You can also use low ohm range to test the speaker impedance without any problem. 2.When you attach the bulb at the B+ line is called the Load, you are basically disconnecting the horizontal circuit supply and hence shutting it down completely and therefore all the other supplies like focus,screen and HV are not energized and therefore in-active and it is as if there are actually dis-connected from the tube.
ReplyDeleteRegards Humphrey