Modification Of DB Meter In Technics Receiver Amplifier Model SA380S
This set had visited me a few months back and I had posted my report and I request the readers to see the article using the following link, before reading further:
This time, the customer brought it in for two purposes: Firstly to modify the DB Meters so as to function in play mode and secondly to test it with a locally built sub-woofer amplifier he brought. The interfacing with the Sub-woofer was found ok, when checked in front of him.
I removed the bottom cover as well as the top cover of the Technics to look at the DB Meter control IC. It was TA7318P.
I looked at the datasheet of this IC from my collection.
I traced the Pins (4) and (6) which were the inputs. I located the tracks and pulled one side up of the two resistors that were going to recording level circuit. Then used two 103 Capacitors (0.01uF/630V) and linked the inputs to the outputs of the volume control.
The VU Meters worked very well when I played the tuner and there was no need to adjust the pots at the IC level. Mission accomplished with satisfaction of different kind, which also got added to the collection!
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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You may check on his previous article on Mismatching Current In New Edge LED Necessitated Bypassing In SONY KD-43X7000E
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