Skip to main content

Posts

Showing posts from October, 2016

Extending the frequency range of Pioneer TX-7700 tuner

TX-7700 is AM/FM stereo tuner manufactured by Pioneer in around 1975 - 1980. This is a basic tuner system which is specifically designed for " rack style " stereo systems. Compare with other tuner systems this tuner is not very popular and very limited information is available on the internet about this model. This tuner is mainly built around HA1138 AM radio receiver, HA1156 stereo decoder and PA3001 (HA11225) FM IF amplifier IC. The TX-7700 which I got is manufactured for Japan and because of that it is designed to work with 100V AC and frequency range is limited to 76MHz to 90MHz. In this quick post, we demonstrate how to tune this stereo receiver to 88MHz to 108MHz by without modifying the circuit(s) of the tuner. In this tuner, the main component which needs to adjust is 5 turn inductor located in FM front end circuit (refer A in below photograph). The frequency range of the tuner can be adjusted by changing the spacings of this inductor. If tuning is getting dif