Overhauling Mechanism Of Harman/Kardon Cassette Deck HK300XM
This was brought to me by a regular customer friend with the complaint that tape did not work and there were intermittent output problems on one channel. As usual, my first duty was to open and clean the inside thoroughly and make it ‘qualified’ to be on my work table. In the process, I saw pieces of two cut belts inside, revealing the reason for failure of deck.
In order for us to replace the belts, we need to remove the cassette door, the knobs and front panel and then take out the mechanism, as there was no way of removing the motor/capstan assembly from the rear due to crammed control board fixed right behind. Have a look at the inside of this Deck, with such a complicated mass of connections:
This deck had two motors, one for turning the capstan and another for play/collection wheels. Let us have a look at the inside of mechanism:
You might notice the press to on button switch array affixed on the front cover of the cassette door. Though the brand is famous, the crude way of design and wiring makes it very difficult to carry out even such a simple work of replacing the belts. Let me be frank to say that I hate to work on such sets. If we removed the boards and carried out any trouble shooting, there was every possibility of wires snapping and sometimes we won’t know from where it came out, even with the help of pictures taken.
I replaced the short flat belt of the second motor and then the capstan motor. Then removed all connectors from the control board, did a dry solder patch up and lubricated the female sockets using a syringe filled with Armstrong Switch Cleaning Oil. Did the lubrication of all connectors on the main board too. Cleaned and lubricated the RC sockets at the rear. The cleaning method that I use is to take a dummy RC Jack, apply the lubrication oil on the socket and insert the jack and turn it clockwise and anticlockwise until the contacts have a clean look. Recording switch is another part that needs to be cleaned without fail. I applied oil and manually pressed and released the switch several times to do that.
Then re-fixed the board and mechanism and applied power. I found it to be working very well. Allowed it to run for a few hours by playing both sides of different cassette tapes.
It worked flawlessly. So, closed the cover and moved it for delivery to the customer.
Mission accomplished collecting another deserving satisfaction as usual!
This article was prepared for you by Parasuraman Subramanian from India. He is 72 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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