Philips 203U

Note: This radio isn't in my collection. It is repaired for a customer

1941

Condition and performance:

	Cabinet	60%
	Reception AM	70%
	Sound Quality AM	50%

Features:

	P.U. Entrance:	Yes
	Tape Recorder Entrance:	No
	Extra Loudspeaker Output:	No
	Loudness:	No
	Treble Control:	No
	Bass Control:	No
	Tone Register Switches:	No
	AM Bandwidth Switch or Control:	No
	Tuning Indicator:	No
	Build-in Antenna:	Yes, metal back-plate
	Build in Ferrite or Window Antenna:	No

Technical Specifications (Partially measured):

	Tubes:	UCH21, UCH21, UBL21, UY21.
	Wave Bands:	LW, MW.
	Intermediate Frequency (IF):	452 kHz
	Loudspeaker:	9668
	Resonance Frequency Fs:	?
	Frequency Range Power Amplifier:	?
	RMS Output Power at 5 Ohms:	?
	Cabinet:	Bakelite, dark brown.
	Dimensions:	24.5 x 16.5 x 13 cm
	Mains Power Voltages:	127, 220 Volts~
	Mains Power Consumption	42 Watts
	Retail Price	f 82.50

Description:

Philips designed this radio in 1939, regarding to the Four European Tube circuit.
See the schematic diagram below, which is basically intended for the Philips 208U, which has as an extra a shortwave (SW) band.

A special item in this Philips 203U radio, is the application of the UY21 rectifier. Later the UY21 is replaced by the UY1N.
Another special part is, the metal back-plate act as an antenna.
Furthermore on the dial scale, you see radio "Kootwijk" printed on LW at around 1800 meters.

Repairs:

After removing the chassis out of the cabinet, the radio is still complete and can play.

Below you see the black paper/tar capacitors, which are visibly broken as well as eletrical leakage.

The brown capacitor is 100 µF 12,5 Volt. This is replaced by a 100 µF 63 Volt capacitor which is smaller in size.
The new capacitor is hidden.

On the front side, you see the bad repairing with superglue in the past. I didn't dare to fix it, because the
bake-lite cabinets are fragile.

All the capacitors and some bad resistors are replaced, so safety and reliability is now optimal for many years.

To get rid of the negative AM detector voltage on the volume potentiometer, the circuit has changed as in the small schematic diagram.
Now the volume potentiometer has only to handle the audio signal, which increases the life time of the volume potentiometer.

Performance:

After repairing this radio, the reception is quite well.
The sound quality is poor, in this case very harsh without any low frequency (bass) reproduction, due to the lack of a loudness circuit.
On the other side, the radio can now play for many years reliable and safely.

Disclaimer:

This radio is directly supplied from the mains power. The high voltage supply is directly taken from the mains power, which means the radio chassis carries the 230 Volt~ mains voltage, which is very dangerous. Before making any repairs on the radio or playing the radio without the back plate, use a safety transformer with separate windings. The insulation of the windings must withstand at least 4000 Volts AC as well as a low leakage current of 0.5 mA~ or less.

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