Vintage Piccolo SR-F300A Transistor Radio Repair

History

​The Piccolo SR-F300A Transistor Radio was a product of Standard Radio Corporation of Tokyo Japan.

This model was first introduced to the US  market in 1960, although I am not sure which year mine was manufactured. 

The SR-F300A is standard AM Radio broadcast receiver of the Super-Heterodyne design. It employs 6 transistors in  a Mixer/Oscillator and three IF (Intermediate Frequency) stages. In addition, it uses a Germanium diode as the Detector to strip the RF (Radio Frequency) envelope from the audio signal. 

A Ferrite antenna is used instead of a whip antenna, the radio is powered by two type N 1.5 Volt Batteries. 

The Piccolo SR-F300A typically came with a brown leather case with strap, emblazoned with the words "Standard" and "Piccolo" in gold lettering. I am not sure what happened to the case for my radio. 

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The Problem

I installed two fresh type N batteries in the back of my Piccolo SR-F300A then powered it on by rotating the Volume control to the position labeled "2".  All that came out of the speaker was this strange "motorboat" sound that change pitch and got higher in frequency  as the volume was turned up. The Tuning control had did not have any affect and no atmospheric sound, typical of AM radios, could be heard from the speaker.

Disassembly

The first step to repairing this 50 year old radio was to take it apart. The back cover just snap fits in place so it comes off pretty easy. The printed circuit board is held in place by two screws and a nut circled in the picture below. Note, I already removed the top screw when this picture was taken.
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The next step was to remove the speaker from the front cover. It is held in place by a screw and standoff. The standoff is also used to secure the printed circuit board in place. See picture below:

The thumbwheels for the volume and tuning control will need to be removed in order to get at the printed circuit board. The volume thumbwheel is held in place with a small nut, while the tuning thumbwheel is held in place with a tiny screw.

Replace Electroytic Capacitors

As electrolytic capacitors age, their electrolyte dries up causing their electrical capacity to drop and leakage current to increase. It is definitely a good idea to replace electrolytic capacitors that are over 50 years old!  I always replace vintage electrolytic capacitors before performing any other troubleshooting. There were eight electrolytic capacitors that needed replaced in this radio. I have circled them in the picture below:

Workspace

I am a firm believer in a clean workspace. I use small containers to hold loose parts during a radio restoration so as not to loose anything. I clean my workspace at the end of each work session. A clean workspace allows me to continue my restore project, free of clutter, the next time I sit down.

Soldering Problems

Standard Radio Corporation decided to place a lots jumpers and some resistors on the foil side of the printed circuit board for this radio. This made replacing electrolytic capacitors difficult. On several occasions, I had to unsolder jumper wires so that I could get to the pads that held an electrolytic capacitor in place, then re-solder the jumpers when finished. I took several close up pictures of the foil side of the printed circuit board so that I had a record of where the jumpers and resistors terminated. 

Problem

I noticed that the cases of the replacement 4.7uF 25Volt Capacitors were extending past the edge of the printed circuit board. This was a problem as it would prevent the printed circuit board from fitting back into the front cover. I had to switch to 4.7uF electrolytic capacitors that had a smaller physical dimensions. The smaller electrolytic capacitors actually had a higher working Voltage rating of 50Volts!   

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Here is a picture, component side, once all of the vintage electrolytic capacitors had been replaced.

Testing

It was time to retest the Piccolo SR-F300A radio, after all of the vintage electrolytic capacitors had been replaced. I reinstalled the Volume and Tuner thumbwheels, inserted two fresh N type batteries in the battery holders, and hoped for the best as I turned on the radio. SUCCESS! The "motorboat" sound was replaced with AM atmospheric noise. I was able to immediately pick up several stations by carefully rotating the Tuner thumbwheel. In fact, I was able to pick up stations across the full tuning spectrum of the radio.  The Volume control worked as expected. 

I was so happy that no further troubleshooting was needed for this radio as I could not source a free copy of schematic. It seemed kinda silly to purchase a SAMs PhotoFact Schematic for $20 when the radio was F-R-E-E free!

Assembly

To assemble the Piccolo SR-F300A radio, first install the speaker back into the front cover and tighten the screw and nut that hold it in place. You have to put the printed circuit board in sideways so as to allow the Tuning thumbwheel to protrude from the slot in the case. Two screw and a nut hold the printed circuit board securely in place. The back cover is just a snap fit to the front of the case. Below is a picture of the finished product.

Conclusion

It always pays to replace the electrolytic capacitors FIRST in a vintage radio before doing any other troubleshooting. I have fixed many a radio with a just a "re-cap" or electrolytic capacitor replacement.

My Piccolo SR-F300A radio in Action!