120V AC Input Transformer Fumed In ONKYO CD Player Model DX-C330
This CD player did a revisit with the complaint that one of the visitors to the customer’s place plugged it in to 230V AC without using the 230 to 120V converter transformer, resulting in burning smell and then the set conked off! I opened the set and checked whether there was any fuse that could have gone and was surprised to see that there was none!
The primary of the transformer was open and so I removed it. Let us have a look at the power supply board:
I took extract of the power supply section from its service manual freely downloaded, in order to study what are the expected voltages from this transformer. I noticed to my dismay that the schematic did not mention the AC input, but secondary DC voltages were mentioned. The diagram showed -32V DC in was regulated to -22 for the display unit and 7 volt for regulated general power supply without any indication of the input DC voltage! Lamp supply for the display was again without any indication of AC voltage! I reverse calculated the AC voltage by applying an approximate formula that we can get about 1.5 times on a full wave rectification. The filter capacitors were of 16V, which meant that the input voltage could be anywhere between 12 to 14 volts. Let us have a look at the schematic extracts:
(Kindly use cntrl and upward arrows to zoom)
When I checked with my techie friends they suggested that the Lamp voltage could be anywhere from 1.5V AC to 3V AC. So I took the transformer to a maker in my town and consulted about possibility of rewinding it so that we need not have to worry about any of the secondary voltages. But the transformer was very badly affected and the bobbin was in bad shape for a reuse. That’s how we decided to make a new transformer that would work on 230V AC, with tapping for 1.5 & 3V AC for LAMP, 6-0-6 and 7-0-7 windings for power supply and 22V AC output for generating the 32V in for display unit. Since the total wattage of the unit was only 13 as mentioned in the model label, he could make a minimum size transformer that could get fit in properly. The extra tapping was to adjust the input voltage if found necessary.
Here is the transformer that I got after waiting for a few days:
You can also see the main board in the above picture, which I removed to check whether any components were damaged due to hike in power supply.
I wired the transformer studying the circuit and positions thoroughly. The connections were crude as he could not fix solder type pins on the transformer due to alternate voltage tapping.
First I connected the board without the loads and checked whether the required DC voltages were present, such as -22V for display, 7 & 8 V for general purposes, as indicated in the first schematic. It was perfectly ok, and then I removed the power and connected the FFC to the board. In order not to peel off the insert assist blue plastic piece; I applied paper tape around it to strengthen it and not to allow a sidewise counter movement when we try to insert the flexible cable into the connector. Let us have a look at this important safety measure taken:
Then fixed the main board back in its place, inserted the FFCs to the connectors and applied power. I was thrilled to see that the set was working very well, with crystal clear display and other functions such as the tray rotating anticlockwise, for checking of CDs loaded. Then I loaded six CDs in it and played and was further amused to see that the output was superb and all functions such as skip CD, open/close, FF & REW, Search etc. were perfectly working.
Then fixed the transformer inside in the place with just one leg screwed and used a cable tie to keep it firm and fixed and then used another for the board on top.
Then played all CDS by using almost all the functions for several hours before fixing the top cover. The set was working very well, to bring a relief to me and give a re-life to the set!
Mission accomplished very well with intuitions and innovations working together to bring a thickly populated satisfaction getting collected to its bag!
The old transformer with its cores, bobbin and fixing bracket Set working very well with its display glowing with precision and accuracy, making reading from a distance possible!
This article was prepared for you by Parasuraman Subramanian from India. He is 74 years old and has more than 30 years’ experience in handling antique equipment like Valve Radio, Amps, Reel Tape Recorders and currently studying latest tech-classes conducted by Kerala State Electronics Technicians’ Association. He has done graduation in BBA degree, private diploma in Radio Engineering and retired as MD of a USA company. Presently working as Consultant to Hospital and other institutions.
Please give a support by clicking on the social buttons below. Your feedback on the post is welcome. Please leave it in the comments.
P.S-If you enjoyed reading this, click here to subscribe to my blog (free subscription). That way, you’ll never miss a post. You can also forward this website link to your friends and colleagues-thanks!
You may check on his previous article on Short Cut Method Used For Polarizer Replacement In SONY LCD TV Model KLV-22BX300
(43)Dislikes
(0)
14 Comments
Leave a Reply
Waleed Rishmawi
May 17, 2025 at 1:40 pm
thanks for the schematics and all the voltages marking on this board. very interesting article. thanks for sharing and have a wonderful blessed day
Parasuraman S
May 17, 2025 at 3:01 pm
My pleasure, dear friend! Many thanks for your lovely comments!
Yogesh Panchal
May 17, 2025 at 2:50 pm
Good Job! Sir
Insert assist blue plastic piece in FFC Cable is always create problem if pilled off from the cable.
Parasuraman S
May 18, 2025 at 10:09 am
Yes, dear! Its a pain once it comes out! Many thanks, dear Yogesh Bai!
Albert van Bemmelen
May 17, 2025 at 3:34 pm
Good to know is that you found the service docs for this Onkyo repair. And after reading your article I also found the service manual for my Onkyo C-7030 also completely free on Elektrotanya!
Strange though was that a search for the Onkyo C-7030 on that website came up with nothing. But after using Google it did find that document on Elektrotanya without any problem!
I am happy with my Onkyo player that never let me down and it is a perfect cd-player and also a MP3 player in one! It no doubt is a decent manufactured brand!
Parasuraman S
May 18, 2025 at 10:11 am
Glad to know, dear Albert! Many thanks!
Henrique Jorge G. Ulbrich
May 18, 2025 at 12:08 am
Very good job, Parasuraman. Really, transformers without voltage identifications are a problem that I encountered too. It´s amazing that you did this maintenance without changing any elcap!!!!
Parasuraman S
May 18, 2025 at 10:12 am
Ha! Ha! E-Cap change is my crazy job and I missed it this time! Anyhow, we shall compensate in the next! (Ha! Ha!) Many thanks!
Imoudu
May 19, 2025 at 4:42 am
Permit me to say you have an ensemble of technical around you working together to achieve same goal..ie making a difference for success.Thanks for sharing.
Parasuraman S
May 19, 2025 at 5:18 pm
Many thanks, dear Imoudu!
Mark J
May 18, 2025 at 2:44 am
It is surprising that there was no fuse on the ac input section. Good job on the repair. Thank for sharing your knowledge and experience.
Parasuraman S
May 18, 2025 at 10:14 am
Yes, how a reputed manufacturer makes a set without a fuse! How did the design get approved! It beats me! Many thanks, dear Mark!
Imoudu
May 19, 2025 at 4:52 am
I need ur help,sony 32" tv with no audio at tuner input,but there is audio at av input,aerial,antenna ok,what do I do to repair this problem
Parasuraman S
May 19, 2025 at 5:16 pm
Ensure that the correct system is selected; NTSC or PAL. The tuner might be defective and needs replacement. Secondly, look for any analogue to digital converter IC which processess the signal. Trace tracks. Look for any leaky or shorted diodes or other components. Download the datasheet of main IC (micro controller IC) and look for input points and continue your check based on that. All the very best!