Philips / Tesla 208U -45

1941 - 1944

Condition and performance:

	Cabinet	80%
	Reception AM	50%
	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, UY1N.
	Wave Bands:	LW, MW, SW from 16 - 50 meters.
	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:	28 x 16 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 an extra shortwave (SW) band.

Repairs:

The power cable is rotten, makes a shortcut and need to be replaced.

The dropper resistor lost also enamel and even the resistance wire is damaged, due to excessive overheating in the past.

Resistors of 1K 9 Watts and 150R % Watts are fitted, so the radio can now operate up to 245 Volts AC.

The loudspeaker coil scratches on the magnet pole.

After removing the loudspeaker, the black capacitor is removed and a new blue electrolytic capacitor of 100 µF 63V is placed.

The loudspeaker can be easily repaired. Dust and rust are removed of the magnet pole.
The black pipe is the old 100 µF 12,5 Volt capacitor.

After fixing the magnet again, it is only a matter now of centerring the speaker cone and the nuts can be tightened.

The baffle doesn't look original.
The power plug may be original.

The bake-lite cabinet is in good condition.

The electronics before repairing.

The electronics after repairing.

In the past the volume potentiometer is renewed.

Further repairs:

An extra leakage resistor and a coupling capacitor of 10 nF 630V is placed between the taper and G1 of the UCH21.
Reason: Prevent the influence of the negative voltage on G1 of the UCH21.
2nd part of the power capacitor of 2x 50 µF has a lot of leakage.
Temporary solution: Replaced by 47 µF 350 Volt.
All the paper capacitors are renewed.
Reason: Paper capacitors have often too much leakage after decades.
Several resistors are renewed.
Reason: The resistance values of the old resistors are increased too much.

The band switch works only on 2 bands and need to be modified, but that is quite difficult, since in the past, this radio is badly repaired.

Performance:

After repairing, the reception of the broadcast stations is better, but still too weak.
The sound quality is poor. Harsh and no bass sound.

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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