A little modification of this good performance receiver. This little radio is an useful travel radio, being compact and having a lot of SW bands and AM+FM. I attached DC plug, an useful feature which is missing from the factory. Sometimes is useful to use a DC external power when the batteries are not available. Unfortunately, there is a very little space inside of the receiver to allow mounting a DC plug, so I studied a bit where to put that plug. The single space available I found, is the position shown in the video. I used a DC plug from an old walkman casette player (in total 3 pins-see my video about SRF-18) which I had to fix in place with glue (unfortunately I could not find other way to make it stay in place, but the glue is strong enough, until now I did not have any problems). The DC plug has enabled the feature of disconnecting battery. Do not be confused by the aspect of 2 wires when you look at the video: there are 3 wires in fact. The gray(grey) wire is not a single one: it is a co-axial small wire recovered from a destroyed laptop, so there are 2 wires in one. It is connected to those 2 pins which interrupts the batteries and allow connection with printed board. So, the red wire is attached at (+) of the DC pug, in the center. The gray coaxial wire is attached to the other 2 pins which allows in the same time the battery disconnection and connection with printed board. I drilled a hole to allow access to DC, and I replaced the spring of (-) at battery, with a spring which is attached at battery interruption circuit, not directly on printed board (the original spring of the radio, due to its shape, can not be used for the modification). I built also a reverse polarity protection with a Schottky diode type 1N5817, because if the polarity is reversed and the device is not protected, it will be a big problem! I SRONGLY recommend that the AC/DC 3V Adaptor to be regulated (stabilized), maybe with LM317 (the cheapest and simplest solution). Do not use any 3V adaptor from the market for this kind of receiver (even if is Sony adaptor) if it is not stabilized! I measured some Sony adaptors and I found 6v instead of 3V, or 7-9V instead of 4.5V! Those are designed for receivers which contain inside a voltage regulator, so those adapters are not suitable for a receiver designed only for batteries. Also, switched-mode power supply has a lot of noise, so is more recommendable to use classical system: transformer + rectifier + regulator (the filtering capacitor must be minimum 2200 microfarad).
Another minor modification is replacing red tune LED with green tune LED and I enlarged a bit the hole to allow more light.
Success!
Негізгі бет Radio Sony ICF-SW20 modification
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