595
Item nr.
| Production | The Netherlands, 2024.
Price was €3. |
|---|---|
| Bands | MW. |
| Semi- conductors | TA7642 (tuner), D467 (amplifier). |
| Cabinet | Wood box. Size 18x18x8cm. |
| Power | Batt; AA cell 1.5V @ 1.2mA. |
| Documents | Slide deck, Schema. |
The Sony 304 has a speaker, transformer, ferrite rod plus tuning cap, and doubtlessly, some transistors.
| Obtained | 8/2024 from own construction. |
|---|---|
| Condition | 8. |
| Disposed | Sold 9/2025. |
The schema is standard for the Kid's type radio, just note that I placed the output transformer in the collector lead of Q1 rather than te usual supply lead. Ferrite rod, tuning cap, and various elco's are easily harvested from the donor radio. The power transformer is used as output transformer; without it, the impedance misfit between te transistor and the speaker (3.2 Ohms) is significant and the sound is very weak and shrill. Unfortunately, I considered the SMD components unsuitable for reuse... and the through hole components were all very small and had short leads. 
There were no 100nF caps I could use, but the diodes in the rectifier were bridges by 22nF each, so I used two (for 44nF) for C3 and C6. In the end, besides the TA7642, I used only electrical components from the Sony (estimated value 1.5 euro), a wood box from the thrift shop (1 euro) and a few bolts and nuts (and solder, say 50cts).
Observe in the inside picture, that the ferrite rod is rather short (63mm). Unfortunately, the selectivity of the Balcony Radio is limited, and I think this is because of a low Q ferrite antenna. In my house, MW is heavily distorted by noise and I receive only Radio Paradijs. Taking the radio on a trip to a clean location (Fort Hemeltje), I could receive Radio Caroline, MCB Radio, and R.Paradijs, though troubled by oscillations below 1000kHz.
Later I got the remark that the capacitor on the transistor is not really needed, so I could have put all four caps on the TA7642 to reduce oscillations. The output impedance of a transistor, connected like this, is in the order of a kiloOhm, so a better match would be obtained with a transformer witth a 110V coil.