The TC-152SD, also called “TC152SD”, is a stereo cassette recorder manufactured in 1978 by the Sony Corporation of Japan. This together with the TC-153SD was the first portable range of professional stereo cassette recorders, based on the newly created Toshiba’s TA7122 general-purpose pre-amplifier integrated circuit (IC). However, in the design of the Sony TC-158SD they went back to basics, eliminating all the integrated circuits, with a pure discrete component system.
For the TC-152SD, they utilised this IC together with the 2SC range of transistors, to create a design specification that surpasses even today's standards. Its circuit is highly optimised, with a low transistor count, which allows the recorder to operate on battery power for a very long time.
Before the invention of the Walkman, if you wanted to travel and listen to music in stereo, then you had to carry one of these on a shoulder strap. It is 378 mm × 108 mm × 238 mm in size and weighs 5.4 kg together with the batteries.
Compared to all the other decks that I have used -- many of them famous brand names with high-end specifications -- this deck has the best sound reproduction capability because of the unique ferrite head design. Once you hear the impressive reproduction quality of this deck, any other deck with a conventional head will never sound as good. This is especially noticeable when you record tapes on it and play them back on a Walkman.
These units are reliable and continue to operate today in many given conditions, with virtually no loss in performance. I serviced my unit back in 1996 with a new belt kit and it is still performing well. Back then, Sony followed Akio's vision of building consumer trust and sent me a replacement belt kit and a service manual free of charge. I remember sending Mr Morita a thank you letter, which I just recently dug up from the attic. This link shows my 1996 letter to Akio Morita.
I decided to service the unit myself, as there is nobody more experienced than me who could service these, besides I would not trust any knob-head specialist in UK. As you can see in the pictures it is unmarked and in mint condition. I even have the original operating instructions with a schematic diagram at the back.
This design is full of innovations that I have still not seen in modern expensive hi-fi today. Below are just some of the features of this machine.
Ferrite and Ferrite (F & F) Glass Head
This tape recorder has one very special and unique secret ingredient that is available only on this range of models and none other. The high performance F & F head has unique properties and is still a closely guarded secret for this model. Extreme hardness and durability, highly polished glass mirror smooth surface means 1/200 the wear of conventional heads. This means that the greatly extended frequency response remains the same today as it did when new out of the factory.
DC-DC Converter Module
For use as a high fidelity recorder, a DC-DC converter is incorporated in the power supply section to generate +24 V, -24 V, and +9 V rails from a +6 V DC input. Only the best quality amplifiers use the split-rail power supply, and the high voltage operation ensures good signal to noise ratio. The DC-DC converter also regulates the power supply to provide a constant level of voltage, ensuring minimum load on the batteries thereby prolonging their operation time.
The DC-DC module circuit, which is inside a metal container, consists of a high frequency oscillator circuit. The circuit is still a closely guarded secret, but having it means that the unit operates on battery power three times longer than conventional power supply designs.
Closed Loop DC Servo Control Motor
For recording on the move, a DC servo control motor operates to minimize vibrations, and keep the tape speed smooth and constant. The servo system maintains tape speed even when the battery power is low.
Dual NiCad and standard battery operation
These machines shipped with a Sony BP-8 rechargeable NiCad battery pack, which provided three hours operation time. The BP-8 was Sony's proprietary design. However, the same battery compartment also accommodates standard UM-1 dry cells, which provide two hours operation time. I have continued to use dry cells, and it operates very well.
The UK model powers on 240 V AC mains, and requires 6 V DC. Its power consumption is 12 watts.
I just love these little stereo sound level meters. They automatically illuminate when the unit is mains powered, or by pressing the “Light” button. The meter function also doubles to indicate the charge left in the batteries.
Other innovations were removable cassette compartment for easy cleaning and servicing, detachable shoulder strap, Dolby noise reduction, CrO2 tape selector, sound limiter, RCA sockets, and headphone sockets.
These units prove to be popular amongst audio professionals and their value tends to increase over time.
The supplied accessories were Sony UM-1 battery pack, mains lead, connecting cord RK-74, and shoulder strap.
If you had the big bucks, then you could choose some expensive Sony branded cassettes, or get a stereo condenser microphone such as an ECM-99. There was a MX-12 microphone mixer, DR-4A headphones, HE-2 head demagnetiser, and LC-28 leather carrying case.
I would love to get my hands on a leather carrying case but to date have not even seen one!
Akio Morita founded Sony in 1958. He was an Engineer and one of the few people in the world who understood what good engineering really meant. Sadly, he passed away in 1999, and was the last of a generation of corporate leaders that transformed the image of the electronics industry from makers of tat to creators of finely engineered electronic products. He encouraged his engineers to innovate, and to create something that endures, and lasts. He hated short term thinking that is currently the trend of many large corporations, which is to create it today, and throw it away tomorrow.
I love vintage electronics, as I can admire and appreciate good design engineering. It is fascinating to study the mechanical and electronic engineering aspects and see how design problems were solved using the technology of that time.
This Article Continues...
TC-152SD / TC152SD Stereo Cassette-Corder
TC-152SD Audio Board
TC-152SD Cassette Deck
TC-152SD Automatic Stop Issue
Power Supply DC-DC Converter
TC-152SD & TC-153SD Mains Cable
TC-152SD Circuit Diagram
Toshiba TA7122 Preamplifier IC
TC-152SD Features & Images
TC-152SD Audio Connections