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Overhauling Mechanism Of Harman/Kardon Cassette Deck HK300XM

By on April 1, 2023
Overhauling Mechanism Of Harman/Kardon Cassette Deck HK300XM






cassette deck repair

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:

harman cassette deck repair

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:

how to fix a harman kardon cassette deck

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.

harman kardon pcb board repair

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.

fixing a cassette deck

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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  1. Waleed Rishmawi

    April 1, 2023 at 4:10 pm

    these equipment in general are complicated to work on. I have once an amplifier from the same brand name and wow, it took me a while to get it fixed. good job on the repair you did an amazing job. have a blessed day

    • Parasuraman S

      April 1, 2023 at 9:10 pm

      Many thanks for your comments, sharing experience and encouragements!

  2. Albert van Bemmelen

    April 1, 2023 at 4:31 pm

    Indeed a master repair after seeing all those wires and different parts that may have caused new problems just by disassembling the motor/capstan mechanism from the unit! I noticed that some of the DIP ic's already were socketed on the mainboard which is not very common. Using Armstrong Switch Cleaning Oil is new to me. Thanks for sharing another cleaning tip.

    • Parasuraman S

      April 1, 2023 at 9:12 pm

      I have mentioned about Armstrong Switch Cleaning Oil, and if I remember well, I have given a photo of it too, in one of my old articles. Many thanks for your expert comments, dear!

  3. Justice Cele

    April 2, 2023 at 5:29 am

    Thanks Parasuraman, quite nice and patience-requiring task.

    • Parasuraman S

      April 2, 2023 at 2:25 pm

      Many thanks for your comments and encouragement!


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