[Dept. of Computer Science]

Philips L4X71AB

Our Department and University.
See my other radios too! (Here is the next one.)

The L4X71AB is one of the more luxereous models among tubed portables. While most of these battery tube radios receive only AM bands (MW and sometimes LW) and are equipped with four tubes, this one receives FM also and has seven tubes. It can be supplied from AC mains and has the possibility to charge the batteries from the mains; if only I could find a 90V rechargable battery!

This is also one of the last Philips tubed portables; the years 1957/58 marked the change from tubes to transistors for portable Philips radios. In 1957 Philips made its first transistor portable; actually three transistorized models came out that year. The next year, 1958, was the year of the last tubed portable, and in 1959 only transistorized portables were made, while tubes were used in home equipement until the late sixties.

Data for this radio
Type Philips L4X71AB, tubed portable
Serial no. W10958A
Bands LW (870-2000 m), MW (186-580 m),
FM (87.5-100 MHz).
Cabinet Wood with leatherette covering,
Size 33x23x12 cm, weight 4.8kg inc. batteries
Tubes DF97 (FM osc./mix.), DF96 (RF stage AM),
DK96 (AM osc./mix.), DF96 (IF stage),
DF96 (2nd IF, FM only), DAF96 (det. and AF),
DL96 (output).
Semicon-
ductors
WE35889 (rectifier), 2x OA72 (FM detector).
Controls Volume, Tone, Tune AM, Tune FM,
Pushbuttons Off, Recharge, LW, MW, FM.
Power AC (110/125/145/220V) 8W, or
Batteries 1.5V @ 200mA and 90V @ 10mA.
Produced The Netherlands, 1957

At first the baby didn't want to play. I changed some tubes, then it had a terrible hum until I discovered that the rechargeable filament battery is also needed when the set is fed from the mains: it filters the 50Hz ripple. The hum was solved with a 3000uF capacitor taking the place of the battery. Altogether the repair wasn't too difficult; here is a picture of the chassis:

Gerard Tel, gerard@cs.uu.nl