My Telefunken Collection

MA 1

Device Type

Integrated Amplifier

Start of Sale

1981

General Description

The MA 1 was Telefunken's high-class amplifier offering in the line of Midi-sized (30x30 cm basic area) Hifi components. Compared to its size, it offers a quite respectable output power of 2x50W RMS and almost all features one would expect from an amplifier at that time, including a power level meter with selectable range. It is part of the M 1 component system, and shares the unusual housing concept: the housing is made of an inner frame, and aluminium profiles attached to it make the 'outer skin'. This housing concept is similar to laboratory devices and in contrast to standard housing concepts of Hifi devices at that time, which were based on bended metal sheets. It gives the whole system a very worthy look, and Telefunken won an industry design award for it. But even among the other M 1 components, the MA 1 looks unconventional with its exposed heatsinks on both sides.

Features

four inputs, tape copy function, loudness, tone controls may be bridged with the defeat switch, noise filter, LED level meters with selectable range, two pairs of speakers may be attached.

Connectors

Technical Data

(taken from the service manual)

Nominal Impedance:	4 Ohms
Nominal Output Power:	2 x 50 W RMS
Peak Output Power:	2 x 80 W
Distortion Factor:	0.1 % at 1 kHz (45 W/4 Ohms),
	typ. < 0.5 % at 40 W/4 Ohms, 20-16000 Hz
Power Bandwidth:	< 10 Hz ... > 40 kHz for K <= 0.7 %
Phono Deemphasis:	acc. to DIN 45 547
Nominal Input Voltages/
Nominal Input Impedances/
Overdrive Reserve (4 Ohms):	180 mV / 470 kOhm / 33 dB (tape)
	180 mV / 470 kOhm / 33 dB (aux)
	180 mV / 470 kOhm / 33 dB (tuner)
	1.6 mV / 47 kOhm / 33 dB (phono)
Output Levels at Nominal
Output Power:	1 mV/kOhm at tape input and 1 V
	input voltage at aux input
	14.14 V at speaker output (4 Ohms)
	0.42 V at headphone output (8 Ohms)
S/N ratio acc. to DIN 45 500:	> 60 dB at tape/aux
	> 60 dB at phono
Channel Separation:	> 55 dB at 1 kHz
	> 40 dB at 10 kHz
Input Separation:	> 80 dB at 1 kHz
	> 65 dB at 10 kHz
Tone Control:	Bass: +13 to -13 dB at 40 Hz
	Treble: +11 to -11 dB at 15 kHz
Balance Control:	0 to -40 dB
Noise Filter:	7 kHz turnover frequency, 12 dB/oct.
Semiconductors:	15 integrated circuits
	25 transistors
	28 diodes
	37 LEDs
Mains Supply:	220/110 V, 50/60 Hz
Dimensions:	298 x 114 x 250 mm

Common Failures

The MA 1 is principally a solid amplifier with discrete power stages. I had so far only one minor failure: a -12V three-terminal voltage regulator, located on the power supply board on the underside. While the +12V regulator has a heatsink, the -12V regulator only supplies the input amplifier board and Telefunken therefore used a 100mA version (78L12, TO-92 housing) without any heatsink. 78xx/79xx regulators however have no SOA protection and are therefore sensitive to overheating, which seemed to have happened to the regulator in this case. I replaced the regulator with a standard 7912 1000mA version, which seems to work well. If you want to make things perfect, use a regulator from National Semiconductor's LM340 series, which are pin-compatible to the standard 78xx/79xx devices, but have an SOA protection and cannot be 'cooked'.

Spare Part Numbers

(taken from the service manual)

		Cabinet Parts
Position	Order No.	Designation
201	339 132 021	front mask, complete
202	339 272 016	indicator window
203	339 272 017	level indicator dial
204	339 917 026	knob guide for treble/bass
205	339 270 010	knob guide for mains switch
206	339 220 016	knob guide for volume
208	339 202 009	knob for treble/bass
209	339 220 015	knob for mains switch
210	339 202 007	knob upper part for volume
211	339 202 008	knob lower part for volume
212	339 270 009	knob frame, 4-fold
213	339 272 018	knob frame, 3-fold
214	339 272 019	knob frame, 1-fold
215	339 220 017	push button (small)
216	339 915 020	pressure spring
218	339 872 024	cabinet lid
220	339 127 006	front mask holder
222	339 137 013	rear panel
224	339 872 029	bottom plate
225	339 060 006	foot for bottom plate
		Mechanical Parts
Position	Order No.	Designation
226	339 872 025	mounting sheet for mains transformer
227	339 872 026	mounting plate
228	339 872 027	mounting angle for headphones socket
229	339 872 028	shielding sheet for pre-amplifier
		Electrical Parts
241	339 332 011	O/P Amplifier Board
Position	Order No.	Designation
C 413/414	339 586 102	Al-electr. cap. 220 µF/50 V
D 401/402/	339 529 017	diode 1 S 1555
405-408
D 403/404	339 529 268	diode 05 Z 9 1 L 0.5 W 9.1 V
FU 401/402	339 570 024	fuse T 2.0 A
R 429	339 502 018	variable resistor 470 Ohm
R 430	339 502 017	variable resistor 1 KOhm
T 401	339 556 393	transistor 2 SA 798 GF
T 402/405	339 556 382	transistor 2 SC 1328 ST
T 403	339 556 383	transistor 2 SA 722 ST
T 404	339 556 385	transistor 2 SA 912 QR
T 406	339 556 384	transistor 2 SC 1885 QR
T 407	339 556 390	transistor 2 SC 2320 GF
T 408	339 556 387	transistor 2 SA 999 GF
T 409	339 556 389	transistor 2 SC 1567 QR
T 410	339 556 388	transistor 2 SA 794 QR
242	339 337 018	Equalizer Board
Position	Order No.	Designation
IC 101	339 575 220	IC NJM 4558 DA
IC 102-104	339 575 087	IC NJM 4558 D
L 101/151	339 347 047	choke coil
243	339 337 017	Electronic Fuse Board
Position	Order No.	Designation
D 501/503	339 529 266	diode SRK 1 100 V
D 502/504-507	339 529 265	diode 1 S 1588
IC 501	339 368 294	IC HA 12002
L 501/502	339 347 046	coil 1.6 µH
RE 501	339 360 006	relay ICA-2 24 V
T 501	339 556 387	transistor 2 SA 999 GF
T 502/503	339 556 390	transistor 2 SC 2320 GF
244	339 337 019	Power Supply Board I
Position	Order No.	Designation
C 818/819	339 588 038	Al-electr. cap. 10000 µF/50 V
FU 806/807	339 572 007	fuse T 80 mA
GR 802	339 520 052	rectifier S 5 VB-20
245	339 337 015	Power Supply Board II
Position	Order No.	Designation
C 802	339 586 100	Al-electr. cap. 1000 µF/50 V
C 805/806	309 414 791	Al-electr. cap. 470 µF/35 V
D 801	339 520 053	diode S 1 VB
FU 801	339 570 029	fuse T 1.6 A
FU 804	339 570 007	fuse T 630 mA
FU 805	339 570 017	fuse T 315 mA
IC 801	339 575 238	IC MC 7815 CT
IC 802	339 575 239	IC MC 78 L 15 ACP
IC 803	339 575 240	IC MC 79 L 15 ACP
246	339 337 021	Level Indicator Board
Position	Order No.	Designation
D 601-624	339 529 259	LED LN 224 RP, red
D 803/804	339 529 267	LED LN 24 YP, yellow
IC 601/651	339 575 241	IC BA 683
R 602/652	339 505 015	variable resistor 500 Ohm
248	339 337 022	Control Board
Position	Order No.	Designation
IC 301/351	339 575 242	IC TA 7322 P
R 301-303/	339 502 019	variable resistor, lockable,
351-353		100 KOhm
R 315/319/	339 502 020	variable resistor, 100 KOhm
365/369
249	339 337 029	Speaker Switch Board
Position	Order No.	Designation
S 702	339 442 021	push button switch (A-B)
250	339 337 023	Sensitivity Switch-Over
Position	Order No.	Designation
R 702/752	339 502 022	variable resistor, 1 KOhm
S 701	339 442 022	push button switch
251	339 337 024	Mains Switch Board
Position	Order No.	Designation
S 851	339 442 023	mains switch
252	339 337 025	Selector Switch Board
Position	Order No.	Designation
IC 201	339 575 087	IC NJM 4558 D
S 201	339 442 025	push button switch
S 202	339 442 024	push button switch
253	339 337 026	Speaker LED Indicator
Position	Order No.	Designation
D 814/815	339 529 251	LED LN 221 RP
254	339 337 027	Type of Operation LED Indicator
Position	Order No.	Designation
D 812/813	339 529 251	LED LN 221 RP
255	339 337 028	Selector Switch LED Indicator
Position	Order No.	Designation
D 805-811	339 529 251	LED LN 221 RP
BU 901	339 540 127	speaker DIN socket
BU 902	339 540 126	speaker clamp socket
BU 903	339 540 125	headphones socket
TR 901	339 312 010	mains transformer
LT 1	339 480 007	power cord with connector
LT 2	339 480 006	power cord with socket
T 901/903	339 556 391	trnasistor 2 SC 2525 GB
T 902/904	339 556 392	trnasistor 2 SA 1075 GB

Available Documents

• User's Manual
• Service Manual

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