Failure Of Motor Control IC BA6209 In KENWOOD KX-880D Cassette Deck
This antique cassette deck was brought to me by a new customer, referred to by one of my regulars. The complaint was that none of the functions worked, but lights were on. I opened the set and cleaned it thoroughly and downloaded the nearest service manuals KX-880HX & 880G from the website. Since the customer informed me that some motor control IC was replaced by another technician who attended the set a few months back for the same problem, I looked at the board and found two motor control ICs side by side.
This is a set with direct drive motors (BA6229 & BA6209). The capstan was run by a brushless DC motor, the head mechanism assembly loading was by another motor and FF/REW was done by yet another. So, there were no belts!
In order to look at the bottom of the board, we need to remove the PCB holding screws from the rear and the control panel case holding screws from the front side, upon which the PCB can be tilted. I managed to keep it upright with a component box kept underneath so as not to strain the AC input wires from the transformer. This is because such sets won’t have bottom cover.
Then found that the BA6209 was the IC replaced by the previous technician. On applying power, the Capstan motor was found running. But none of the press to on buttons of Play, FF or REW worked. The cassette was stuck inside and could not be removed as the head mechanism was engaged and the eject door could not be opened. I removed the motor connectors from the board and used an external power supply to rotate the Mechanism Loading motor located underneath on a trial and error basis with touch and go tactics.
The input voltage was also varied from 6V step by step until motor turned. Upon one of the trials, the mechanism slid back and I could then eject the door and remove the cassette. The + & (-) had to be inverted until the correct position of polarity rotated the motor to the desired level. Since the motor was mechanical without any speed control unit within, there was no danger in trying it out.
Then I checked the voltages to the uController IC and checked its crystal. These were normal as per the service manual.
Then I checked the voltage to the suspected IC and found it to be normal. The IC was getting slightly hot even after removing the load. Then I checked whether the trigger pulse was reaching its drive control pin 7.
The pulse was reaching, when I pressed the play button, but the IC did not respond, indicating that it had gone bad. I fetched new ICs (bought two pieces to be on the safer side) and replaced this IC, upon which the set worked very well when power was applied.
Looking through the circuit diagram, I tried to assess what caused the IC failure and replaced 0.1Caps on the loads of both ICs. Then removed the cassette door sliding it out, then the inner cover to expose the function of play and gear wheels. Then inserted a sheet of thick paper on the leaf switch that senses door closed. This switch is typical that it opens when pressed releasing the ground from the other side, which goes to the uController door open sensor pin through two transistors. I did a lot of study of the functions of uController and checked all connected circuits related to the mechanism before replacing the IC and in the process enriched my knowledge on such feather touch mechanisms.
Then applied power, upon which the head mechanism motor rotated once or twice to place itself in correct position. For your information, the truth table of the three leaf switches that are controlled by the rotation of the loading motor is given below the uController IC descriptive diagram. I had to refer to both the service manuals to learn these.
(Please use cntrl+upward arrow to zoom to a readable image)
Then fixed the inner cover back and loaded a cassette and applied power. I was glad to see that it functioned very well on all modes; Play-Fast Forward-Rewind-Pause. I played both A and B sides of the cassette and also tried some of my own.
The set worked perfectly, upon which I switched off and re-assembled the set to how it was before. Once again I tried a few more cassettes and the set was found working wonderfully well. Misson accomplished with a lot of knowledge gained and bulgy satisfaction getting added to the collection bag.
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.
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Albert van Bemmelen
February 22, 2025 at 11:33 pm
Odd that these motor driver ic's like the BA6209 got bad so soon after they previously already were replaced by another engineer. I suppose it had also something to do with the bad 0.1uF caps?
Parasuraman S
February 23, 2025 at 9:17 am
Many ICs available in the market are bad and they fail too soon. Surrounding components do contribute, though! Many thanks, dear Albert, for your expert comments!
Waleed Rishmawi
February 22, 2025 at 11:41 pm
So what was the cause of the IC failure? I enjoyed the article and thanks for sharing. Have a blessed day.
Parasuraman S
February 23, 2025 at 9:18 am
Could be the quality of the IC. Many thanks, dear friend!
Francisco Maciel
February 23, 2025 at 12:24 am
Hello from Mexico.
Question:
How do you (and all tech-friends) manage or deal how much to charge to customer per a repair?
Best regards
Parasuraman S
February 23, 2025 at 9:21 am
Depending upon the complications, time spent and the value of the set. The charges vary according to the situations. It cannot be specified or fixed though we do have some directions from our Technicians' Associations. Thanks for your comments!
Mark J
February 23, 2025 at 5:13 am
Parasuraman another great cassette deck repair article. I aspire to be as good as you are at repairing these. I learn a lot from your articles.
Parasuraman S
February 23, 2025 at 9:22 am
It is the encouraging comments from experts like you, that help me move forward and take up new challenges, dear Mark! Many thanks!
Mark J
February 24, 2025 at 4:04 am
Parasuraman you are welcome. You are far more an expert than I am.
Parasuraman S
February 25, 2025 at 4:43 pm
No such comparisions. It is your humbleness that makes you say so! Each and every one of us is a unique personality and opening up the way we are all supposed to. Many thanks, dear Mark!
MUYKIT
February 23, 2025 at 10:24 pm
Thanks Engineer Parasuraman.Though I last handled casette players quite some while ago, I always had a feeling that the general driving motor operation system was under considerable load caused by draggy(not turning easily) casettes. Its a pitty when the system is faced with a C90 casette to play.Motor driver ICs may well not escape the overload damaging effect. So I think.
Parasuraman S
February 25, 2025 at 2:47 pm
Very true! It's an issue of torque and load! Thanks for your comments!
Yogesh Panchal
February 23, 2025 at 10:55 pm
Good Job!Sir
Parasuraman S
February 25, 2025 at 2:47 pm
Many thanks!