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Leon Crampin · 10th Oct 2017, 9:53 am

For general information, I've measured the current drawn from the battery terminals of this set when fed from an accurate 9V external power supply. FM was selected and the volume set to minimum.

Using an AVO Model 8, the current draw settles at about 27 mA, there being some change as the output transistors warm up. This set has previously had the quiescent current set accurately according to Grundig's published service sheet (in German).

Leon.

One characteristic of these sets when set to an AM band is high oscillator radiation. A look at the circuit shows that the oscillator output is fed to a coil on the ferrite rod to achieve mixing with the incoming signal. You could exploit this by using your second set (or any other suitable AM set) to detect the oscillator radiation from the set under investigation. The oscillator runs high and the AM IF is 460 kHz, meaning that if you tune your suspect set to a quiet spot at the low frequency end of the MW band, the oscillator will be receivable on a second set towards the high frequency end of the same band. (Tuned frequency + 460 kHz). I tried this test and it works well.

10th Oct 2017, 9:53 am	#35
Leon Crampin Octode Join Date: Nov 2005 Location: Surrey, UK. Posts: 1,874	Re: Grundig Concert Boy 1100 For general information, I've measured the current drawn from the battery terminals of this set when fed from an accurate 9V external power supply. FM was selected and the volume set to minimum. Using an AVO Model 8, the current draw settles at about 27 mA, there being some change as the output transistors warm up. This set has previously had the quiescent current set accurately according to Grundig's published service sheet (in German). Leon. One characteristic of these sets when set to an AM band is high oscillator radiation. A look at the circuit shows that the oscillator output is fed to a coil on the ferrite rod to achieve mixing with the incoming signal. You could exploit this by using your second set (or any other suitable AM set) to detect the oscillator radiation from the set under investigation. The oscillator runs high and the AM IF is 460 kHz, meaning that if you tune your suspect set to a quiet spot at the low frequency end of the MW band, the oscillator will be receivable on a second set towards the high frequency end of the same band. (Tuned frequency + 460 kHz). I tried this test and it works well.