grundig: Grundig Satellit 600 sharp audio volume decrease & failure

Dear friends.

I met a problem with one of my Satellit 600 models: After several years of normal working, the sound started to show sharp volume decreases without any apparent reason, from time to time, but always deteriorating and increasing the ellapsed time of low volume, until it was absolutely impossible to get a reasonable loudspeaker sound (but without sound distorsion!)

Following the information provided in the Forum by Charles Weigel (23.Jun.12) regarding "Grundig Satellit 600 repair - No LW/MW/SW/FM ", I have found that the origin of the presently described behaviour is very similar to the one described by C. Weigel (after a hard work around the "Programmumschalters MOS IC 601 MC 14066 B" -program changing- and T601 muting transistor circuits)

Refering to the link provided by C.W., Satellit 600 Power Switch (80 KB), the failure was finally found because of the presence of an unstable voltage (between 2 and 3 Volts) on Power switch position 2 C, when the radio was turned ON. This voltage should be 0 Volts when ON, but instead it was driving transistor T601 just in small conductive state via resistor R929 (39K) (T601 is used to mute sound when switching among bands, or tuner frequency quickly, or to external Audio input, avoiding so cracks and noise)

Once again the origin of the problem is printed board contamination, in this case almost sure because of leakage from dry batteries (former owner carelessness produced a non working set when I received it)

At the time, in some areas, the cooper printed lines had dissapeared, and also some other remaining lines were in a very poor condition. The isolation among some of them was very poor (for example, the AC connector printed lines were not present) After some rewiring and deep solder surface cleaning where possible, the set has been working perfectly for years, as described.

But since some areas are not accesible (without tearing apart the whole set, specially component side), time has played against the printed board characteristics.

So, after a new cleaning procedure around Power switch pins and heating them by soldering iron, the set is again working well. Until next occasion...

 

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