A little more Harman/Kardon ST-7 info

A little more Harman/Kardon ST-7 info

Postby MisterFishey » Fri Nov 04, 2011 9:54 pm

As an owner of a Harman/Kardon ST-7, I thought I would add some interesting information about this table not covered in the TVK museum:

- It is mentioned that the one circuit board contains two ICs. For a linear tracker, this is remarkable in and of itself, but the even more remarkable fact is that both ICs are actually just 6-pin optocouplers, the still-available 4N27. This means that this table is 100% repairable from an electrical standpoint, as all other parts are available as well.
- The three unlabeled controls for 45rpm, Stop, and 33rpm, are capacitive touch controls - quite advanced for 1976! They work extremely well and are magical to use.
- Though the ST-7 was built in Plainview, NY, the DC hall motor and motor drive assembly was constructed in West Germany by Pabst, and is labeled as such. There is no schematic or board layout of the motor drive assembly in the service manual.

Though the ST-7 is electrically simple, mechanically it is not, and has 12 listed mechanical adjustments in the service manual. The main age-related issue is that the tonearm assembly rests on a rubber roller that degrades over time. This roller is an odd size and is somewhat difficult to replace (though easier than changing belts on some tape decks), but once replaced, the turntable is good to go. It is really a wonderful table, perhaps not a sonic masterpiece but certainly a design masterpiece!
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