Fully Leaked Capacitors Found In Nakamichi Tape Deck
This antique tape deck was brought to me with the complaint that it was erratic and all controls work intermittently. Even though the Deck was neat and had not collected much dirt inside, which I saw after opening, I just did a routine cleaning up. Downloaded a free service manual from the web and studied its power supply circuit and checked the voltages.
The voltages were very much lesser than specified. So, disconnected the power, discharged the capacitors and checked the ESR of all the capacitors in the power supply. Found some of the capacitors showing NIL ESR. So, removed the tank capacitors one by one. Just see the condition of the board and the capacitors that I found in this deck:
As you can see from the pictures, the capacitors had leaked heavily, legs rusted and broken! How this set was working even intermittently is something that baffled me! I replaced all the electrolytic capacitors on the power supply board. While replacing, as usual I observed not only the polarity, value as per original circuit diagram, its reference number on the board, but also the marking on the board.
This board had its positive side marked with a thick green round. But in one place, the marking on the board was on the wrong place! The positive marking on the top side of the board and ‘+’ mark on the bottom side of the board were not matching! Definitely a PCB design mistake! Just see the pictures. The first picture shows the system followed in the board. Rest is already marked.
I have seen many Nakamichi devices before and have observed that while they claim to be one of the best in audio field, the design of their circuit as well as boards are crude. You can find a lot of resistors and capacitors connected under the PCB, on the pattern side and a lot of such patch work type of changes, which they would have done afterwards as a modification. But in professional class sets, we should not see such patch works. It is possible at the prototype development stage itself. But some minor modifications might become necessary, but cannot be to this extent!
After replacing all the capacitors and cleaning the board, I powered the set up and found it to be working well and all voltages were correct as per its schematic. Incidentally, the 6800/25V was not available in the market.
As these were mounted parallel on the board to make a total capacitance of 13,600uF, I used one 10000/35 and another 4700/35 in its place, the total of which came to 14700uF, which you can see from one of the pictures below. I am giving the pictures of the set working, along with a few other snaps which are for those who might be interested to know its construction:
Finally, here is the picture of all the electrolytic capacitors that I changed on the power supply section.
Needless to say that another work got added to my ever growing satisfaction bag!
This article was prepared for you by Parasuraman Subramanian from India. He is 69 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 repair article below:
https://jestineyong.com/intermittent-in-two-lg-lcd-monitors-repaired/
(73)Dislikes
(0)
14 Comments
Leave a Reply
Albert van Bemmelen
March 5, 2020 at 9:04 pm
I wouldn't have expected anything less but leaking capacitors in this new repair from you. Indeed strange that the polarity for the power e-caps on the mainboard was wrong in this expensive design. It probably also would imply that this machine was faulty long before the standard warranty period had ended?
Parasuraman S
March 5, 2020 at 10:36 pm
Whenever such mistakes take place, the manufacturers issue an internal note that will be circulated only to the assembly and service staff indicating the error and to take caution. These practices are in vogue even in giant companies, as rarely such mistakes will go unnoticed to the last stage!
Yogesh Panchal
March 5, 2020 at 11:20 pm
Good job Sir!
Many local manufacturers are using this gimmick for confusing outside Technicians.
Parasuraman S
March 6, 2020 at 1:44 pm
Yes, I do not want to name them here. Very cheap guys. I even called one guy having factory, and ridiculed him for erasing the IC numbers and marking polarity of electrolytic capacitors wrongly on the board. Even the diode markings were wrong!
Vinod kumar Kaushik
March 7, 2020 at 4:03 am
I admire your talent. I'm professionaly a teacher who have a keen interest in gramophone players and cassette decks.I enjoyed your article.
Parasuraman S
March 7, 2020 at 9:25 pm
Very nice to know about you and your interests! A lot of cassette deck repairs have been published by Jestine Yong. You can search for those! Many thanks!
Waleed Rishmawi
March 7, 2020 at 8:28 pm
congrats on a job well done. it is a good practice when taking out the capacitor to always check for positive and negative markings because I have seen it so many times before ( in this case too) that capacitors are marked wrong and installed wrong. thanks for sharing and have a blessed day
Parasuraman S
March 8, 2020 at 11:33 pm
Many thanks for your input and encouragement, which I appreciate so much!
Robert Calk Jr.
March 9, 2020 at 12:39 pm
Good job, Parasuraman! Manufacturers are the biggest cause of e-waste!
Parasuraman S
March 10, 2020 at 10:07 am
Yes, dear! Very true!
ulises aguilar pazzani
March 12, 2020 at 3:48 am
grate Job Sir , looking into it, good eay
Parasuraman S
March 15, 2020 at 1:57 pm
Many thanks for your comments! It helps!
Humberto
March 12, 2020 at 4:24 am
Hi Parasuraman, I've really enjoyed reading your article, great repair.
Parasuraman S
March 15, 2020 at 1:58 pm
Many thanks for your comments! It really helps!