Technics Receiver SA-424 - Tuner doesn't do it anymore

Hello,
I do have a receiver make Technics SA-424. It was stored in the dry basement for many years. As it is today raining cats and dogs, I grabbed the "forgotten" receiver and cassette deck RS-M260, hooked them up to the power line and speakers. However, I had to realize that the tuner did not function at all. The receiver has a buildt in analog and digital metering to show the frequency selected. Both did not work. Except the analog meter (to show the field strenght) at least lit up, nothing else. The ability to select the preset channels and to tune is completely lost. All the LED diodes did not light up. The LCD scale to show the channel frequency selected was dead, too.
However, the amplifier works very well in conjuction with the cassette deck. Pretty good sound.
To tell you I'm lost at the moment. Beforehand opening the receiver, I would like to spread the information into the forum. May be anybody has an idea how to remedy the problem. I hope, that there is an easy solution to remedy the problem reported, e.g. a microfuse to be replaced etc.
Thanks for a qualified answer.
 
Check the lithium battery at points 901-902 you need to measure 4.5 volts. Followed if there is power in the radio part and the part that switches the audio signal.
Thanks for the hint. I'm going to follow this up. I just wonder why there should be an additional lithium battery installed inside the Technics SA-424 machine as there is a battery compartment on the back-side to hold 3 RR batteries. Those batteries are to support the storage of the radio stations pre-selected.