SERVICING LG DVD HOME THEATRE MODEL HT-155DD
This DVD player was brought to me with a complaint that DVDs/CD won’t play but USB and FM were ok. Customer also told me that it was never used ever since bought and lying in its carton for months together! On checking I found that it ejects and closes properly, and I could hear CD running. So, I opened the set. Then I tried playing a CD to observe what happens.
The CD was running at its normal speed, eye unit was moving up and down, Red laser light could be seen from the side. (Caution: Never look at a laser light directly, as it may affect the eyes and we might even lose our sight!) But after running, and movements of the eye unit, the CD gets ejected with a display ‘Disk Error’:
I cleaned the lens and tried with a few DVDs as well with the same result. As the inside of the player was very clean, there was no need for any cleaning. I disconnected the power cord and removed the boards for detailed study.
I noticed that there were no dry solders and no bulgy capacitors. The ESR of Electrolytic capacitors in the power supply board were ok. This has two transformers, one for generating low voltages and another for generating 34V (I think it is for audio amplifier section). I took a snap of the voltages written only at the bottom. The main board consisted of uController, CD Unit Controller, FM tuner, Aux input, Amplifier section, Speaker Outputs. See its rear:
When I checked the ESRs of capacitors on the main board, I noticed that ESR reading of two 470uf/10V caps and four 10uf/16V were either at brim or above the levels. Marked these capacitors with a sketch pen on its top, for identifying and removing it later.
Replaced these carefully, as the capacitor leads were bent and soldered on the other side. Almost all these capacitors were mounted from the component side, but had no connecting tracks on the top. See the pictures below:
Using desoldering linz wire, removed the solder from the leads thoroughly, and carefully straightened the bent lead with a sharp knife, taking care not to tear the hair line tracks, and removed the cap and replaced with a new one after testing it. (Nowadays, if you do not check a new component, before replacing, that itself can give trouble! That is the standard of quality!). Cleaned and lubricated all the connectors as well as the sliding motor paths. Put the PCBs inside the cabinet temporarily, and interconnected. Switched on and ensured that all voltages were in order.Played a CD.
CD started playing, but it was skipping and was also sluggish, indicating that all was not well in the sliding motor section. Checked whether there was any dust particle or some other obstructing things on the rods on which the eye unit moves. I could not find any. So, replaced the sliding motor. Reconnected everything and switched on. The player worked very well! Why should a motor fail in an unused DVD player is anyone’s’ guess!
I played a few DVDs and CDs and kept it on for a few hours. Tried the USB and FM and these were also working perfectly well.
I connected a single speaker that I used for testing all the outputs and these were also ok.
Fixed all the screws and cover properly. Here is a picture of the motor and capacitors replaced:
Another job completed satisfactorily.
This article was prepared for you by Parasuraman Subramanian from India. He is 66 years old and has more than 30 years’ experience in handling antiques equipment Valve Radio, Amps, Reel Tape Recorders and currently studying latest techs classes conduct by Kerala State Electronics Technicians’ Association. He was a BBA graduate, retired as MD of a USA company.
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You may check on his previous repair article below:
https://jestineyong.com/servicing-philips-pet81698-dvd-player/
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Yogesh Panchal
February 15, 2017 at 3:40 pm
Good job! sir.
Anthony Aichem
October 27, 2023 at 5:07 pm
I have same type of this model
Mine the ic got burnt the number on the transistor got burnt out too .
Am asking if you could help with number ,the transistor is located at the other side of the power panel responsible for sound with 6 legs starting with STR ...
Albert van Bemmelen
February 15, 2017 at 3:55 pm
You are as always very good in fixing CD/DVD players and Audio sets Parasuraman S! I myself often find it much easier to repair a SMPT unit than it is to repair CD/DVD players. So again Kudos to you! (By-the-way: I thought that Kudos was Japanese but it apparently originates from the Greek κῦδος. And means Glory or Fame). So it is well deserved!
erik blankers
February 15, 2017 at 4:55 pm
Hello Parasuraman,
Where dit you get a replace motor, new one or sparepart???
nice job
Parasuraman S
March 12, 2017 at 3:52 pm
New spindle motors are available. We have to remove the spindle and use it. Since these motors are working on pulses generated from the control IC, it will work.
John david
October 20, 2021 at 3:31 pm
Helo sir,
I have difficulties identifieing which ic is responsible for any fault on home theater main circuit.
Am a beginner.
Ruben
February 15, 2017 at 9:26 pm
thank you for the dvd repair article ,yes ! sometime a dvd motor will go stock up ,usually the dvd is long time no play , perhaps the magneting wire inside of the dvd already getting rush or burn out . you done very well , thanks, Ruben
Jim Whalen
February 15, 2017 at 10:03 pm
Nice job on finding the caps and motor problem. Just a note : you might want try cutting the cap legs off then desolder the ones that are bent over and they may fall out for you ,so you will not have to worry about the tracks lifting.
Parasuraman S
March 12, 2017 at 3:54 pm
I do this many times, provided access for a cutter is available for insertion.
zaheedi farjan
February 20, 2017 at 1:26 am
Hello sir its really magic what i have learn so far with u n i thank you a lot with appreciation even am a senior technician 30 years of career in electronics so once more hats off sir.plse i have a request i would like to know how i can test very simply a ccfl back light tube
Best regsrds
Zaheedi farjan
Parasuraman S
March 12, 2017 at 3:55 pm
There are many ways to do it. I would advise you to buy one backlight tester with multiple voltages, which are readily available in the market.
Oluwatosin
October 29, 2017 at 11:44 pm
please can you help me out, customer brought LG DVD home theater ht355sd to me, when I power it on it eject by itself when I try to push it back it still come out and I have checked everything therein, I don't see anything burn inside. please help me out.
Bassey
February 4, 2018 at 12:21 am
Great job, you don't know how many people you've helped through this articles.
There's one thing I'd like to find out from you please, I have this LG home theater HT306 with 16-pin powerboard connector to the main board. I want to know what voltage the V-CTRL is supposed to be. Thank you
seree
April 12, 2018 at 11:15 pm
Hey guys may someone have a circuit schematic of power supply of LG HOME THEATER DH3140? I couldn't find it in the internet.
Joseph
April 1, 2019 at 9:43 pm
Sir after reading all this l do have LG home theater ht914 with high pitched sound assistance please write an article for that and thank you
Banula Yeran
November 18, 2020 at 1:06 pm
Hello sir,
I have LG HT356SD model, It does't responding. sometimes DVD CD automatically opens when powered on, I pessed close button but does not go in. Switched to USB, it does not read it, keeps displayed USB.
& FM radio also not working.
I did a factory reset, but problem still exists
Please help me
Benie Vær
December 16, 2020 at 4:15 pm
Hello., What can I do to my DVD player., Same LG model as the one above. Mine powers on but then immediately writes "protection" and never does anything else?
Nsa
April 15, 2023 at 6:43 am
Hello sir..
The system is powered but, the 34v that power the amps doesn't supply voltage, what could be the problem?
Cyril
September 20, 2023 at 2:51 pm
Sir, I have a LG HT355SD DVD Home Theater. This works well. But Display is not working. How to make this a reality?