Sony TC-152SD DC-DC Module

An ideal dc-dc voltage converter exhibits 100 % conversion efficiency; however, in practice efficiencies from 80 % to 90 % are obtainable with conventional components. The latest integrated circuits using MOSFETs can achieve between 95 % to 98 % efficiency.

This is a switched mode chopper circuit, which is very efficient in converting the voltage. The small transformer, known as the chopper transformer, contains the necessary windings to generate the required voltage rails. Majority of dc-dc converters use the buck converter principle, where an oscillator circuit energises the primary winding of the chopper transformer, and the taps on the secondary side provide the voltage rails.

It is very common for a transistor to fail, however since a replacement was unavailable, it was logical to build a new circuit that could provide the +24 V rail and install it into this module.

Many firms manufacture dc-dc modules, and it saves time getting readymade modules than designing and building one yourself. I managed to find a number of commercially available modules that provided +24 V and -24 V rails from a +6 V input.

Circuit Board

It is remarkable that Sony engineers were able to make a circuit so small, and it is a very neat high-density construction.

I decided to build a replacement circuit that converted +6 V DC into +24 V DC and install it within the module. The circuit I designed and installed was based on modern technology, hence it should outlast the lifetime of the tape recorder.

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