[Dept. of Computer Science]

Philips BX690A

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

This radio was donated to me; a word of grace to the previous owners is in place here.

Data for this radio
Type Philips BX690A
Bands LW (715-2000m), MW (185-580m), SW1 (37-50m),
SW2 (31-42.5m), SW3 (24-31.8m), SW4 (19-25.8m),
SW5 (15.5-20m), SW6 (13-17m).
Cabinet Wood, 59x35x25cm. Weight 14.5 kg.
Tubes ECH21 (osc./mixer), EAF42 (IF stage and AVC),
EAF42 (AF and det.), 2x EL41 (pushpull output),
EM4 (tuning eye), AZ1 (rectifier), 2 dial lights.
Controls Vol/off, tone/bandwidth, bands, tune.
Power AC (110/125/145/200/220/245V) 60W.
Speaker 21cm, 7 Ohm.
Produced The Netherlands, 1949.
Price was 425 guilders.

The Philips BX690A has a peculiar output stage, consisting of a push-pull output, but there is no tube working as the phase inverter. Instead, one tube is driven directly from the preamplifier and the other tube has no signal on its control grid; the two cathodes are connected to each other and carry the signal, fed back from the output transformer. Thus the second tube is actually driven from the output of the first tube, comparable to the series-balanced output, but here the driving signal goes all the way through the output transformer (big job with 10 wires).

The band indicator is also nice: rotating the band switch elevates the entire dial such that the chosen band is the lowest one visible.

I replaced almost all wax-paper capacitors in this set, and had to replace the ECH21 mixer tube. But still the sound isn't very good so I suppose I had to replace a few caps more. Also the volume control is a bit scratchy. Just a BFO and the 10m and 80m bands would turn it into a nice ham receiver!

Gerard Tel, gerard@cs.uu.nl.