TRK-1255ER inside View

The inside of the Hitachi TRK-1255ER shows an example of wonderful electronic engineering. These radios would have been hand constructed, and people would have soldered these wires by hand, which is a skill and industry hard to find today. They built these radio cassettes to last almost forever, before recycling became so important, and therefore they still have some value.

The 10E1HS is a 3-watt 8 Ω loudspeaker, which sounds clear. It is an open-magnet loudspeaker that sounds very reminiscent of the 70s.

This little mains transformer still operates today.

The HA1319 is an audio amplifier IC for tape recorders manufactured by the Hitachi Corporation. It usually drives a complementary symmetrical power amplifier stage consisting of 2SD170, and 2SB370 transistors. This IC provides equaliser characteristics, automatic gain control (AGC), and operates on voltage as little as 4 V making it ideal for portable applications.

This is the complementary symmetrical power amplifier stage showing the transistors. One transformer would split the audio phase, whilst the other recombines it at the output to drive the loudspeaker. This type of output design was very typical of the 70s, and later designs in the 90s became output transformer-less (OTL).

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