Blaupunkt B52W

1952

Condition and performance:

	Cabinet:	90%
	Reception AM:	70%
	Reception FM:	70%
	Sound Quality AM:	70%
	Sound Quality FM:	70%
	Sound Quality P.U.:	70%

Features:

	P.U. Entrance:	Yes
	Tape Recorder Entrance:	No
	Extra Loudspeaker Output:	Yes, 7000 Ohms
	Loudness:	No
	Treble Control:	Yes, switchable
	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:	No
	Separate AM/FM tuning:	No

Technical Specifications (Partially measured):

	Tubes:	ECH42, EF80, EBF11, EL11E.
	Wave Bands:	LW, MW, FM from 87.5 - 101 MHz
	Intermediate Frequencies (IF):	473 kHz, 10.7 MHz
	Loudspeaker:	18.5 cm diameter, permanent magnet type
	Resonance Frequency Fs:	?
	Frequency Range Power Amplifier:	?
	RMS Output Power at 4 Ohms:	4 Watts
	Cabinet:	Bake-lite, dark brown.
	Dimensions:	50.3 x 33 x 21 cm
	Mains Power Voltages:	110, 127, 145, 220, 245 Volts~
	Mains Power Consumption	48 Watts
	Retail Price	DM 239.50

Description:

The Blaupunkt B52W is the little brother of the Blaupunkt F511WP.
The EL11E tube is in fact an EL84 tube with a socket adapter.
The radio works regarding to the super hetero-dyne principal, but there are only 4 tubes applied in stead of the usual 6 tubes. It seems tubes like the ECC85 and EAA91 are missing.
Well, the FM ratio detector is done by 2 crystal diodes RL24.
The ECH42 works also as an oscillator for the FM.

The EF80 has 3 functions at the same time.

Audio pre amplifier. (< 20 kHz)
IF amplifier for AM and FM. (473 kHz and 10.7 MHz)
Tune-able HF amplifier for the FM reception. (> 87.5 MHz)

Repairs:

Selenium rectifier is replaced by a 1N5408 diodes with a series resistor of 150R 5 Watt.
Reason: High voltage supply was too low and is now 250 Volts DC which is a perfect value.

Other repairs need to be done for safety reasons, like replacing leaked capacitors, but so far the condition of the original components are quite well.

Performance:

The audio performance is quite well, even without the application of a loudness circuit. The EL11E has a local feedback circuit which increases the low and high audio frequencies, so the type of sound is full.

Disclaimer:

The build in power transformer is only meant for the heater voltage of 6.3V~ and the different primary voltages. The high voltage supply is directly taken from the mains power, which means the radio chassis carries the 220 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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