The MA 2 is the amplifier of Telefunken's 1981 entry component system M 2. It is a splendid example for the 'keep it basic' philosophy of this system. The only feature that could be counted as 'extra' is the loudness switch: even the auxiliary input that was otherwise considered indispensable is missing. Fortunately, they didn't leave out the phono input and preamplifier, so one could at least attach a record player without additional (switch) boxes...
Loudness switch, 2x20 W RMS
not available at the moment, have no docs
Of course, the most sensitive section of every amplifier is the power section. The MA 2 makes no exception of that, and the lack of protective circuits makes things even more critical. Fortunately, the one unit I got only needed the power transistors replaced. Selecting replacement types is not difficult, since 20 watts per channel is a relatively small output power. Just beware that the transistors are darlington types. Using normal transistors will make the amp seem to work in the first moment, but the higher base bias will result in a hefty quiescent current - the repair won't last for long ;-)
In this case, I have used BD647/648 transistors as replacments, cheap and easily obtainable types.
(taken from Telefunken's 1981-1991 Service Handbook)
|ICs, Transistors, Diodes|
|339 555 251||transistor 2 SB 751|
|339 555 129||transistor 2 SA 817 A|
|339 556 412||transistor 2 SC 1583|
|339 556 299||transistor 2 SC 1815 GR|
|339 556 466||transistor 2 SD 837 P,Q|
|309 001 221||transistor RCA 17520|