I got an old National Panasonic tape recorder, model no: RQ-2157, and decided to break it down and see how it works. Being a newbie, I forgot to note down the wiring and connections and dismantled all the individual modules. My question is about how the recorder is powered. The recorder can be powered using 2 "D" batteries supplying a DC voltage of 6 V, or it can be powered by AC supply. If it is powered using AC, it has two modes, 110-125 V or 200-240 V, 50-60 Hz. There is a dial that can be turned to switch between these two modes.


I assume that the dial is a potentiometer from the way it looks. It is rated for 250 V, 2.5 A ~. A wave was next to the rating, so AC? I don't know.
The AC power is supplied through an "AC in" socket, with two round prongs.
The hollow on the bottom seems to be the spring holding the inserted cable in place. This socket is soldered to a peculiar board. I have no idea what this board is for or what it does. There are two diodes on it. The dial is connected to it. The stepped down 6 V taps from the transformer is connected to it. The connections from the 6 V batteries are soldered to it. Two wires go out of this board to power the main board.



The pale red and white wires issuing from the "+" and "-" points on the small board go to the main board.

Please explain how this all works. How is the AC converted to DC to power the main circuit? Thank you.

 

What you have there is a centre tapped transformer, using two diodes to create a full wave psu..




http://www.learnabout-electronics.org/PSU/psu11.php

 

What you have there is a centre tapped transformer, using two diodes to create a full wave psu..

View attachment 117852

Thank you so much, I understand the AC-DC conversion part. Could you explain what that black dial thing is? Where does that fit into the circuit? I tried searching online with the part no: Hosiden HXW133, but I couldn't find any useful information, except that it's some kind of a voltage selector/fuse thingy.

 

It will be a two position switch, changing the input voltage to the transformer primary.

 

It will be a two position switch, changing the input voltage to the transformer primary.

Thank you and I'm sorry to ask this again but, how does this two-way switch fit into the above circuit. There are three leads, one connected to the live wire of the AC power supply. How about the other two?

 

It will be a change over switch for the primary winding voltage.