Item nr.

Philips B1X42A Table top

Small tubed FM radio

Data for Philips B1X42A
ProductionThe Netherlands, 1965.
Price was 199 guilders.
BandsMW, FM (88-108MHz), IF is 452kHz (AM), 10.7MHz (FM).
TubesECH81 (AM conv, FM IF), EBF89 (IF), ECL86 (preamp and output).
OA90 (limiter), 2x AA119 (ratio det.), BA102 (AFC), B250C100 (rect.), AF124 (FM amp), AF125 (FM conv.).
CabinetPlastic. Size 37x17x16cm. Weight 3.3kg.
PowerAC 110/127/220V @ 27W (measured).

The Design

The tube era ran towards its end in the mid sixties. Tubes were still cheap as AF amp and AM reception, but appearently, for the FM tuner, transistors were already better or cheaper. Read designer Rudolf Drabek about this.

Around 2015, also the AM era ran to an end, so I wanted a small tubed radio with FM reception. The type shield mentions a power consumption of 30W, but the measured consumption is 27W, a little lower as is frequently the case with tube sets.

Obtained1/2016 from John; sn=338132.

This Object

The external condition is good, and the radio is complete. When I got it, it had some nasty hum and audio oscillations.

I replaced a handful of capacitors, and measured the voltages to find everything OK. The top of the cabinet is clearly stressed by the heat of the three tubes. I refixed the metal sheet that is there to stop the heat.

After two years, in February 2018, it needed another repair. The FM didn't work on the higher frequencies of the band, and the lower frequencies dropped after some time of playing, a problem that seemed to worsen over time. I thought I should first check the components of the AFC, but when measuring R41 and R11, I saw that R7 had a bad solder joint. I found that voltage +2 was only 7V (instead of 9.2). Voltage +2 is the supply for the transistorized FM front end, and is derived from B+ through a voltage divider consisting of R9 and R7/R6. I could increase +2 with R7, but I found that R9 had gone up to 41k. I replaced it, and also R6, which measured 5k2 rather than 4k7. During operation, R9 would get warm, further increasing the resistance, of course, which caused the FM stations to drop all after half an hour of playing.

Part of Gerard's Radio Corner.
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