Aetherkruiser AK1500 2nd Version

1950

Condition and performance:

	Cabinet	60%
	Reception AM	90%
	Sound Quality AM	90%
	Sound Quality P.U.	90%

Features:

	P.U. Entrance:	Yes
	Tape Recorder Entrance:	No
	Extra Loudspeaker Output:	No
	Loudness:	Yes, only on bass
	Treble Control:	Yes
	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

Technical Specifications (Partially measured):

	Tubes:	ECH42, EF41, EBC41, EL41, AZ41.
	Wave Bands:	LW, MW, SW from 16 - 50 meters
	Intermediate Frequency (IF):	452 kHz
	Loudspeaker:	AD 3700AM
	Resonance Frequency Fs:	?
	Frequency Range Power Amplifier:	15 - 20,000 Hz
	RMS Output Power at 800 Ohms:	3 Watts
	Cabinet:	Wood, light brown lacquered, dark brown side panels.
	Dimensions:	38 x 26 x 21 cm (knobs excluded).
	Mains Power Voltages:	110, 125, 150, 200, 220, 250 Volts~
	Mains Power Consumption	40 Watts

Description:

Aetherkruiser shares the same production line as Erres in the Hague. The chassis and the electronics are the same as Erres, but the cabinet has a different style.

Repairs:

After removing the back-plate, I saw immediately that the condition of the electronics are very bad. The loudspeaker isn't original. Many of the paper/tar capacitors are visible broken. Also the tube sockets of the EL41 and AZ41 are overheated and make internal shortcuts.
The volume potentiometer isn't original and has no loudness tap. Usually this makes the sound harsh and very thin.

Many resistors are also increased in value.
For the reception part, this is restored with new resistors and capacitors.

For the audio part, a Philips AD3700 AM of 800 Ohms is placed. The power amplifier is also build from scratch with EL86, EL84 and EBC41 tubes.
The volume potentiometer is also replaced with a loudness tap. The AZ41 is replaced by 2 diodes 1N5408 and the power capacitors are also renewed.
See the schematic diagram below for the power amplifier and power supply parts.

Schematic of a power amplifier for 800 Ohm loudspeakers.

The amplifier output power is approximately 3 Watts in 800 Ohms.

Further repairs:

Both potentiometers are renewed.
Loudspeaker is now the Philips AD 3700AM.
Reason: Old loudspeaker isn't original and the speaker cone is also damaged.
New AM detector circuit is applied.
Reason: Preventing DC component on the volume potentiometer.
Dial cord is renewed.

Performance:

After repairing this radio, the reception is good and the sound quality is very well, due to the output transformer-less (OTL) power amplifier.
OTL power amplifiers have a very wide frequency range, usually from 15 - 20,000 Hz.

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Download the schematic diagram