Kücke KS E-42

Data

General

• Manufacturer: Kücke
• Model: KS E42
• Year of manufacture: 80s
• Made in: West Germany
• Color:
  • Front: chanpage (brown button); gold, chrome, black (black button).
  • Case: Brown for front: chanpage; Black for front: gold, chrome, black
• Type: (Mono/Stereo) (Analog)
• Remote control: yes via KS V32 + system control cable: BOX1, BOX2, On/Off
• Power consumption: 15 W/400 W (idle/volume)
• Dimensions: 445 x 60 x 365 mm (WxHxD)
• Weight: 10,5 kg
• New price approx:

Connections

• Number of inputs:
  • 2x stereo: 2000 mV, 97 kOhm.
• Number of outputs:
  • 2 x speaker pairs

Technical Data

• Continuous sinus power (at THD).
  • 8 Ohm: 80 W (0.01%)

4 Ohm: 110 W (0,01%)

• Dynamic power
  • 8 Ohm: n.b.
  • 4 Ohm: n.b.
• Total harmonic distortion: n.b.
• Attenuation factor: n.b.
• Frequency response: 100 kHz High frequency protection circuit switches off at approx. 40kHz.
• Signal to noise ratio: 102 dB at 5 W and 100 Ohm source impedance
• Stereo channel separation: 87 dB

Special Features

• Die-cast aluminium housing is also the heat sink
• Toroidal transformer, to reduce magnetic interference in the amplifier circuit, shielded by additional housing
• Can be switched on remotely by control cable via V32
• Electronic protection circuits effective at:
  • High frequency, DC voltage at speaker output

Overtemperature output stage transistors Overtemperature of mains transformer

• Defect of a device fuse on the power amplifier board is indicated by LED.

Remarks

Stereo power amplifier in service-friendly modular design. Classic push-pull power amplifier with bipolar power transistors in AA-B circuit bridgeable to mono. Because of the weak power supply an increase of power up to 280W can only be expected with a loudspeaker impedance of 8 Ohm.

Other models of the same series:

• Tuner T22
• Preamplifier V32

Error symptoms of the aging electronics

Cracked electrolytic capacitors with loss of capacitance on the power amp modules due to high temperatures. Replace suspected electrolytic capacitors with low-ESR types, e.g. Panasonic, at best all per power stage module board.

• Cold solder joints on the input rectifiers

--> Check the solder joints of the board and re-solder suspicious ones. Because of the screwed on heat sink at the bridge rectifier bridge rectifier, cold solder joints often occur here as a result of the application of force. This can be seen if the heat sink is too tight when the heat sink leans in one direction.

• Protective circuit of the output stage switches off after a longer period of operation because of too high offset.

Parameter drift of one transistor in the discrete differential input stage (important to use paired equivalent transistors (current gain factor Ic_beta + Ube) from reputable manufacturers). Pairing is no longer witchcraft with the universal component testers available today!!!

Loudspeaker signal first on one side, then at higher volume on both channels.

Clean oxidized contacts of output relays with emery cloth or replace relays with new compatible type.

--> Oxidised RCA sockets (main cause) or cold soldered joint due to mechanical force

--> Oxidized contacts input relay (Attention: Siemenstype is not pin compatible with DIL-relay). Clean contacts or replace relay contacts with wire bridges.

Missing basses, sound image shifted from the stereo center

--> Loss of capacitance of the only coupling capacitor on one of the power amp boards

Only the experienced electronics engineer should dare to repair his valuable Kücke electronics. ATTENTION: Inside the output stage there are voltages exceeding 42V, the VDE guidelines have to be observed. Often more is broken by the intervention (repair attempt) than repaired and ends up in the worst case in the online auction house. Burned traces, misaligned trimmers (you should know what you're doing if you mess around with trimmers for no reason without knowing their function) etc. are the result.

If in doubt, contact the competent repair service of Kücke see link on the company profile!