A Dead CRT TV Was Brought Back To Life. Model: Mieler ML21TV
According to the customer that brought this CRT TV set to my shop; it was working fine but the next day he tried to power it on, it did not.
The stand by light was on. That was an indication that the horizontal circuit and the power supply in both primary and secondary are in good working condition. To make sure all was well, I measured the voltages reaching the HOT, and I got 85 volts there. All the outputs in the secondary section of the power supply were there and stable.
From experience, this TV set should be working but for some reason, it was not. There was no remote control with this TV set and I could not find one for it.
The only thing that I could think of at this time was the EEPROM chip. Sometimes, when operating the TV from the main buttons, the program inside the EEPROM chip freezes and do not function any more. The answer to my problem was the remote control but since there was not remote control for it, I decided to do it the other way and hope it will work.
The EEPROM chip that I was dealing with in this problem was 24C08A. This is a common IC and it should be easy to replace and re program. I got one IC in my shop. I soldered it without reprogram it. I just want to see if the TV works or not. When I powered it, the TV worked and came on but only for a few seconds because the program found on that EEPROM was not the same as the TV’s.
Unfortunately, I do not have a programmer in my shop. I went to see another TV technician, also a friend of mine who has one. He down loaded the program on the new EEPROM. I installed it back on board and powered up the TV set. The TV worked just fine.
This was my first time I deal with this kind of problem. I had to ask a lot of questions and I got a lot of answers. Bottom line, I got the TV fixed and that what counts.
This article was prepared for you by Waleed Rishmawi, one of our ‘Master Authors’ and currently working in the Bethlehem area of Palestine repairing electrical and electronic equipment. Please give a support by clicking on the social buttons below. Your feedback on the post is welcome. Please leave it in the comments.
By the way if you have any good repair article that you want me to publish in this blog please do contact me HERE.
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shehab kably
July 23, 2013 at 4:08 pm
modern and high quality devices uses some strategies by design to protect eeprom from corruption such as power-on reset (POR) and low voltage reset
(LVR) circuitry . to cope with unexpected removal of power combination of hardware and software is used to allow EEPROM operations to complete before power to
the MCU drops below its minimum operating levels. From a hardware design standpoint, the main
considerations are: providing an early indication to the software that power has been lost, and providing
enough reserve power to complete any pending EEPROM operations
beh
July 23, 2013 at 5:55 pm
HI WALEED
if you are suspect to EEPROM IC you should install a new EEPROM IC on the circuit . new means a blank EEPROM IC with same code of course in this case the micro control will check the IC and AUTOMATICALLY generate the EEPROM program and sends in inside ic and/or if you have programmer first you have to save the program of EEPRom on your hard disk of your pc and then via the program of your programmer make this ic blank and then reinstale the blank EEPROM in the circuit most time 80-90% this works. of course this depends on the micro of the set under repair .99% the program inside the EEPROMs are getting defective not the EEPROM IC itself
hope this help you
beh
Waleed Rishmawi
July 23, 2013 at 8:10 pm
Shehab and Beh. I appreciate the input...
shihab kably
July 23, 2013 at 8:43 pm
I would to thank you Mr.Waleed for the informations you provided and the opportunity to discuss this subject
Waleed Rishmawi
July 24, 2013 at 4:03 pm
you are welcome shehab.
beh
July 23, 2013 at 11:50 pm
HI WALEED
if this tv set still is in your shop you may do this test
and tell me the result
thanks
beh
Waleed Rishmawi
July 24, 2013 at 4:04 pm
Beh: no, I do not have it in my shop..customer already took it but I thank you. I will give it a try if I have the chance and will let you know
beh
July 24, 2013 at 6:36 pm
HI WALEED
i want just to know how much this way of repairing would work specially for older sets and older micros . let me know
thanks
beh
Waleed Rishmawi
July 25, 2013 at 4:06 pm
Noted. thanks
Sanan
September 1, 2013 at 3:57 pm
Hi Waleed. Nice article. I would like to ask you the way how the circuitry works in case of if stand by light is on then the technician can conclude that the horizontal circuit and power supply primary and secondary sides are in good condition. Is there any relation between these circuits? Your comment on this question is highly appreciated. Thanks in advance.
Robert
October 4, 2013 at 6:27 pm
Thanks Waleed for sharing the article and to all of you for sharing your knowledge and experience.
raymundo saura
October 6, 2013 at 9:32 am
i am still learning, and very happy recieving this articles i love it thanks and GOD bless
ben daligdig
June 15, 2019 at 4:22 am
hello,what is the problem in panasonic tc-25fg20ru when it is power on the relay clicking.the power is on and off.i tried to many replacement in primary side,secondary side and even the flyback i already replace but the problem i cannot solve.tanx