Aristona SA4135A

Condition and performance:

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

Hint: Press the KG, LG and FM button at the same time for a better audio high frequency reproduction of the P.U. entrance.

Features:

	P.U. Entrance:	Yes
	Tape Recorder Entrance:	Yes
	Extra Loudspeaker Output:	Yes, 5 Ohms
	Loudness:	Yes, only on bass
	Treble Control:	No
	Bass Control:	No
	Tone Register Switches:	Yes, bass and treble.
	AM Bandwidth Switch or Control:	No
	Tuning Indicator:	Yes, EM84
	Build-in Antenna:	Yes, FM and SW
	Build in Ferrite or Window Antenna:	Yes, LW and MW
	Separate AM/FM tuning:	Yes

Technical Specifications (Partially measured):

	Tubes:	ECC85, ECH81, EF85, EABC80, EL84, EM84, EZ80.
	Wave Bands:	LW, MW, SW from 16 - 50 meters, FM from 87.5 - 100.5 MHz
	Intermediate Frequencies (IF):	452 kHz, 10.7 MHz
	Loudspeaker:	AD 3460M
	Resonance Frequency Fs:	?
	Frequency Range Power Amplifier:	30 - 15,000 Hz (After modification).
	RMS Output Power at 5 Ohms:	3 Watts
	Cabinet:	Wood, dark brown lacquered.
	Dimensions:	53 x 35 x 23.5 cm
	Mains Power Voltages:	110, 127, 145, 220 Volts~
	Mains Power Consumption	55 Watts
	Retail Price	?

Description:

Repairs:

• Tuning indicator EM84 doesn't act.
  Reason: Resistor R5 of 470K shows an endless value and is replaced by 470K 1 Watts.

• EM84 still doesn't act.
  Reason: The manufacturer forgot to solder the brown wire to G1. This is fixed and the EM84 works now perfectly.

• FM audio has distortion.
  Reason: Capacitor C40 of 4 µF 70 Volt has dried out and is replaced by 4.7 µF 63 Volt. Also the FM ratio detector trimmer is re-adjusted.

• Amplifier output power is too low.
  Reason: Loudspeaker AD 3460M is connected to the 2.5 Ohms tap transformer and is now reconnected at the 5 Ohms tap.

• Amplifier output power is still too low.
  Reason: Cathode resistor EL84, R32 of 2x 360 Ohm parallel increased in value and is replaced by 180 Ohms 3 Watts.

• Low frequency reproduction has too much distortion.
  Reason: Too much gain in the bass part, as well as the stronger modulation of the today's AM and FM broadcast stations.
  
  • Negative feedback circuit is completely removed and is replaced by resistors of 3K3 and 150 Ohms. This makes the frequency response more flat and reduces the distortion.
  • Loudness capacitor C42 is changed from 8.2 nF into 5.6 nF 630. This results in a more full and warm sound since the feedback circuit changed.
  • Bass control switch is connected parallel over C42 of 5.6 nF (Loudness capacitor).

• High frequency reproduction is poor and the power amplifier tends to oscillate at high frequencies.
  Reason: Paper/tar capacitors C48 of 2200 pF and C56 of 3300 pF are increased in  value and have also electrical leakage.
  
  • C48 of 2200 pF is replaced by a series network of 10K 3 Watt and 1000 pF 2000 Volt. This gives a better high frequency reproduction on FM.
  • C56 of 3300 pF is replaced by 4700 pF 1000 Volt. This results in a better noise and whistling reduction on the AM bands.
  • Treble controls are made passive. The capacitors are now connected to ground potential.  This results in a better treble control and improved stability of the power amplifier.

• High voltage supply is 230 Volts DC which is a bit too low.
  Reason: EZ80 is partially worn out and is replaced. The  high voltage supply is now 250 Volts DC which is a good value.

Performance: