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'LIVEWIRE?' · 10th May 2012, 11:50 am

Martin, I've just found some Blaupunkt service data, including an audio amplifier circuit dating from the early 70s(a 7631 series). In this the NTC is connected between the bases of the AD156(AD162)&AD157(AD161) and is a 60ohm type with a 270 ohm resistor in parallel. Unfortunately I have trouble scanning in legible copies of documents otherwise I'd post the circuit on the forum. It's a conventional DC coupled amplifier, using silicon transistors(BC108c and BC178A or similar in the early stages) Some versions include a protection lamp in series with the speaker connection, which detects any DC flowing due, e.g., to a leaky speaker coupling capacitor.

10th May 2012, 11:50 am	#9
'LIVEWIRE?' Rest in Peace Join Date: Mar 2006 Location: N.W. Oxfordshire(Chipping Norton) Posts: 7,306	Re: Blaupunkt Frankfurt repair Martin, I've just found some Blaupunkt service data, including an audio amplifier circuit dating from the early 70s(a 7631 series). In this the NTC is connected between the bases of the AD156(AD162)&AD157(AD161) and is a 60ohm type with a 270 ohm resistor in parallel. Unfortunately I have trouble scanning in legible copies of documents otherwise I'd post the circuit on the forum. It's a conventional DC coupled amplifier, using silicon transistors(BC108c and BC178A or similar in the early stages) Some versions include a protection lamp in series with the speaker connection, which detects any DC flowing due, e.g., to a leaky speaker coupling capacitor. Last edited by 'LIVEWIRE?'; 10th May 2012 at 11:57 am.