503
Item nr.
Three tube pocket radio.
| Production | The Netherlands, 1955.
Price was fl 89.50. |
|---|---|
| Bands | MW (200-550m). |
| Tubes | XFW40, XFW40, XFY51. |
| Cabinet | Plastic. Size 105x70x22mm. Weight 200gr. |
| Power | Batt 22.5V and 1.5V. |
| Documents | Vintage, RadioMuseum, schema. |
The Tecla radio is a quite unique product: a pocket radio with three hearing aid tubes. It came in a cardboard box, with guarantee card, user manual, earpiece, and sleeve, which I all have. 
| Obtained | 11/2019 from Maarten Bakker; sn=01245. |
|---|---|
| Condition | 7; very complete set, tubes replaced, chord patched, hardly works. |
| Disposed | Sold 3/2024. |
The inside shows a battery compartment and a small pcb, measuring just 60x54mm, containing all the electronics. When I got the radio, the earpiece wire was cut in pieces, which I soldered, and I made a B+ battery from 8 CR2032 cells. The radio produced some barely audible noise in the direct vicinity of my mini transmitter, but clearly underperformed. I replaced the two 10nF capacitors under the chassis, both were very leaky, and this improved the sound a lot! I loudly heard my transmitter over several meters. The coupling capacitors were almost capacityless so I replaced them as well.
Unfortunately, here I shorted the B+ voltage against the filament circuit and blew the first tube! So, though my results were very promising, I had to defer the work until a new XWF40 has been located.
To prevent further damage, I soldered a 2k resistor in the plate battery lead. Under normal operation conditions, the 0.5mA draw only reduces the tension by 1V, but it limits the shorting current to 10mA which is safe for tube filaments. 
Fellow collector Fred provided me with some hearing aid tubes, DF64 and DF67, which can be used in its place. After mounting the DF64, I found out that the output tube XFY51 was also blown! I replaced it with a (somewhat more powerful) DL67 from Fred's donation. After getting all the solder connections right, the set played again.