The Philips model 930A was known
as a "gothic" radio and often called a "ham box" because of its shape.
The distinctive pointed cabinet is made of an early plastic material (similar
to thin Laminex) called "arbolite" and made by Philips. The pattern
is a dark rose wood colour but has a better shine. It is a fabricated cabinet
instead of molded and has a bakelite speaker bezel of the Philips logo.
This is a 4 valve receiver for the broadcast band, built in the period 1931-1933. It is a 240 volt model with serial number 35427D. It has a regenerative detector using a REN904 triode and two audio stages using another REN904 followed by a B443 pentode. The rectifier is an 1801 (or G504 or PV430 or RGN504). These are 4 volt filament valves with British bases. There is a main steel chassis holding the 4 valves, mains transformer, capacitors (all in one block) and the resistors. The tuning capacitor has a solid dielectric in the form of sheets between the vanes of the capacitor. The speaker is a normal Philips style "chinese hat", which has the speaker driver inside the cone, rather than on the back.
CONTROLS
The radio has only four controls and is easy to operate. In the centre is the mains ON/OFF toggle switch. At the right is the TUNING control and indicator window. It is marked 0 to 100 and illuminated from behind. At the left is a BAND selection switch which selects the broadcast and long wave bands. Between the BAND switch and toggle switch, is a REACTION control which acts as the sensitivity and volume control. If the REACTION is turned fully clockwise, then you will hear a whistle for each station, as you tune across the band. You should reduce the REACTION, until the whistle stops, and this is the loudest and most sensitive position of the control. By reducing the REACTION further, the volume is reduced. Leaving the control in a position to cause a whistle, means that the detector is oscillating and it may interfere with neighbouring radios. At the back of the radio are four sockets, so that a long wire aerial may be connected to give the best reception. There is also and earth socket. The detector is so sensitive to the aerial, that if a wind is moving the aerial, it can be heard in the received signal. At the rear are another two sockets for a phono connection.
RESTORATION
The radio was brought over from Scotland as personal affects. During the move, the valves were lost and the speaker cloth was pushed in. The light brown speaker cloth had the owners name written on it in ink near the bottom. I removed the cloth, ironed it to remove the wrinkles and reclamped it in a slightly lower place, so that the name is not visible. The ON/OFF switch was missing, so I mounted another one in the original hole and replaced the mains cord. I replaced the dial lamp which is the same as a 6 volt automotive bulb. The speaker was in good condition and worked. The frequency selection switch was warped with age, and some contacts broken. These were repaired. I repaired three open circuit wire wound resistors. I obtained new valves. I powered the set up slowly with a VARIAC and monitored filament voltage and HT. After a few hours on the VARIAC the set was at normal voltage and began to work.
PERFORMANCE
The radio is easy to tune. Just turn the REACTION control fully clockwise, and tune across the band till a strong whistle is heard. Then reduce the reaction control until a clear station is heard at the required volume. The set needs a large aerial and is not very sensitive. Audio volume is adequate but certainly not excessive.
Copyright
Ray Robinson
