Philips Philetta BD254U

1955

Condition and performance:

	Cabinet:	50%
	Reception AM:	80%
	Reception FM:	60%
	Sound Quality AM:	70%
	Sound Quality FM:	70%
	Sound Quality P.U.:	60%

Features:

	P.U. Entrance:	Yes
	Tape Recorder Entrance:	No
	Extra Loudspeaker Output:	Yes, 5 Ohms
	Loudness:	Yes, only on bass
	Treble Control:	Yes, continuous.
	Bass Control:	No
	Tone Register Switches:	No
	AM Bandwidth Switch or Control:	No
	Tuning Indicator:	No
	Build-in Antenna:	No
	Build in Ferrite or Window Antenna:	Yes, LW and MW
	Separate AM/FM tuning:	Yes

Technical Specifications (Partially measured):

	Tubes:	UCC85, UCH81, UF85, UABC80, UL41, UY85.
	Wave Bands:	LW, MW, SW from 25 - 50 meters, FM from 87.5 - 100.5 MHz
	Intermediate Frequencies (IF):	460 kHz, 10.7 MHz
	Loudspeaker:	AD 3460X (Not original)
	Resonance Frequency Fs:	152 Hz
	Frequency Range Power Amplifier:	?
	RMS Output Power at 5 Ohms:	?
	Cabinet:	Bake-lite, brown, white spray painted.
	Dimensions:	29 x 21 x 17 cm
	Mains Power Voltages:	110, 127, 220 Volts AC/DC
	Mains Power Consumption	50 Watts
	Retail Price	DM 196.00

Description:

The Philips Philetta BD254U is a small but complete Philips radio, made in Germany. It is a good second radio next to the large tube radio's.

Repairs:

First of all I have cleaned the radio inside. The cabinet has a tear and some chassis fixing points are broken. This is fixed by the use of a small amount of super glue.
The loudspeaker isn't original. It should be the AD 2460, but in the past it is replaced by the AD 3460X by a previous owner, which has usually a higher efficiency in the mid-high regions. The AD 3460X has a larger magnet as the original loudspeaker.
Before making any measurements and testing I have replaced the most important 2 capacitors. Then I connected a series bulb of 220V 60W and found out, there is no short cut inside the radio and the power capacitor is in good condition.
Later when connecting directly to to mains power, I found out the FM isn't working. The UCC85 tube has almost no emission and is regenerated.

Capacitor C5 of 22 nF is replaced by a Wima capacitor of 22 nF 1600V-.
Reason: The original Wima capacitor is exploded. Normally you can leave this capacitor out for making further measurements, but for a better AM reception and the use of a "virtual" ground, it is better to use this capacitor.
Capacitor C86 of 10 nF on the UL41 anode is replaced by 10 nF 1000V (ERO).
Reason: When this capacitor gets broken, the output transformer, UL41, UY85 and the dropper resistor can be get damaged. Also the increased cvalaue of the old capacitor results in a poor sound quality on the AM reception wave bands.
Tone control capacitor of 6800 pF is replaced by 6800 pF (ERO) 1000V.
Reason: Leakage which results in a cracking sound of the potentiometer. Also the increased value results in a bad tone control curve. Now the tone control curve is optimal.
Coupling capacitor C82 of 15 nF is replaced by 22 nF 630V.
Coupling capacitors need to be replaced at first before the UL41 and output transformer gets damaged, due to positive grid voltage. A larger value doen't really matter. Theoretically, the radio increases a very little bit in the bass audio frequencies.
Capacitor C81 of 100 nF is replaced by an electrolytic capacitor of 10 µF 350V.
Reason: Leakage. Increasing the value results also in a bit less power supply hum.
Cathode resistor R55 of 180R of the UL41 is replaced by 220R 3W.
Reason: Due to the higher mains power voltage of 230V~, the anode current of the UL41 becomes too high. Now the anode current is 41mA at 220V-. The anode dissipation is now 9 Watts, which is the limit regarding to the UL41 datasheet. A higher cathode resistor results in a less class-A setting, but the life time of the UL41 increases and in many cases, the amplifier power output increases even.
Cathode capacitor of 100 µF 12.5V on the UL41 is removed.
Reason: Reduction of the amplification gain, due to the stronger audio modulation of the current broadcast station on the FM and AM bands.
The power supply hum has also decreased and the loudness function works better. The radio can now play loud without distortion.
Since there is no negative voltage feedback applied, the tone control curve keeps the same.
Grid capacitor C80 of 4700 pF to the UABC80 is replaced by 4700 pF 1000V (ERO).
Reason: Leakage results in a variation of the negative grid voltage of the UABC80. It is also the cause of the a scratching potentiometer. Now the scratching has disappeared.
The loudness capacitor C79 of 4700 pF is replaced by 3300 pF 400V.
Reason: The AD 3460X loudspeaker gives less in the bass. Now the sound is more full and pleasant.
Capacitor C76 of 27 nF is replaced by 22 nF 630V and is connected to the hot taper of the volume potentiometer.
Reason: Leakage results in AM and FM negative detection voltage on the volume potentiometer, which can better be avoided. The life time of te volume potentiometer will also be increased.
Capacitor C86 of 4700 pF on the output transformer is replaced by 4700 pF 1000V (ERO).
Reason: Safety reason for eventually touch currents on the loudspeaker output entrance.
Capacitors C66 and C67 of 5000 pF are replaced by 4700 pF 1000V (ERO).
Reason: Safety reason for eventually touch currents on the P.U. input entrance.
Capacitor C69 of 47 nF is replaced by 47 nF 1000V (ERO).
Reason: This capacitor is for the Automatic Gain Control (AGC) on the AM wave bands. Leakage results in audio distortions of strong AM broadcast stations. Also the capacitance is often increased, which results in a too slow AGC.
Capacitor C11 of 470 pF is replaced by 470 pF 2000V (Wima).
Reason: This capacitor is connected to the AM antenna input. A leakage can result in damaging the SW HF coil as well as too high dangerous touch currents for the human body. It is strongly recommended to replace this capacitor for optimal safety.
Electrolytic capacitor C72 of 5µF for the FM ratio detector is replaced by 4.7µF 63V.
Reason: Distortion on FM reception, especially at receiving of strong broadcast stations.
FM De-emphasis capacitor C75 of 2700 pF is replaced by 470 pF.
Reason: Increasing the treble of FM broadcast stations. The type of sound is now more hi-fi alike more open and more friendly.
MW button is broken and is filled with hot glue. Now the MW button is more sturdy.
2 Zener diodes of 15V 1.3W are connected in anti-series and is connected parallel with the scale lamp.
Reason: During heating up of the radio, the scale lamps gives too much light. Now the amount of light is the same all the time and the life time of the scale lamp has increased.

On the pictures, you still see the old ERO capacitors, but these capacitors are all replaced for optimal safety and performance.

Performance:

After repairing the Philips Philetta BD254U, the reception of the broadcast stations is good, but the sensitivity on the FM band could be better. Probalbly the UCC85 needs to be renewed. Due to the more sensitive AD 3460X loudspeaker, the small radio can play very loud without distortion.

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.

Home

Back to Picture Gallery 2

Contact Kees van Dijke

Download the schematic manual.