Telefunken M 204 E - VU-Meter Circuit Operation; Oscillator Circuit Function; End Switch-Off Mechanism

Pos. Spare part Price
Nr. em No. group
+ 15 tension spring for brake, left 339 900 619 K+
+ 16 tension spring for forward lever 339 900 603 K +
+ 17 clamp spring for switching rod 339 915 713 H+
+ 18 pressure spring for connecting rod 339 905 703 H+
+ 19 pressure spring for pushbutton
lever 339 905 707 K+
+ 20 tension spring for rest flap 339 900 706 N +
+ 21 tension spring for pushbutton lock 339 900 723 K+
+ 22 tension spring for stop button 339 900 724 K+
+ 23 tension spring for lifting slider 339 900 711 K+
+ 24 tension spring for switching lever 339900719 K+
+ 25 tension spring for notched lever 339 900 705 N +
+ 26 tension spring for recording slider 339 900 722 K+
+ 27 tension spring for additional brake
and reverse lever 339 900 602 P+
106 1 set of 5 rods (one each) 339 825 717 B
1 set of plastic washers 5 each 339 942 021 F
1 set of metal washers 5 each 339 940 014 T
F. Electrical parts
110 sliding switch with spring 339 440 603 Cc
111. sockets carrier, compl. 339 420 605 L
112 bracket with mic. sockets and 2 switches 339 420 606 L
113 loudspeaker socket LB 3 339 540 001 Vi+
114 5 pole socket 339 540 014 A
115 Radio/Micro-switch 339 440 604 A
116 distance tube, black 339 935 017 K +
118 mains lead 339 480 603 E
119 potentiometer 5 KOhms R 12/22/31/41 339 500 608 F
120 potentiometer 25 KOhms R 11/21 339 500 703 J
121. mains transformer 339 310 602 P
122 clamp for mains lead 339 870 707 H +
123 shaded pole-motor E98, U 28/2 50/60cps. 339 300 607 Ss
124 voltage selector plate 339 410 607 |
125 six-functiones selector 339 440 609 M
126/129 slider for switch S 101/201 339 400 608 G
127. distance tube, yellow 339 935 015 K +
128 . slider for switch S 301 339 400 607 F
metal holder for sliding
switches S 101/201/301 339 870 703 K+
130 amplifier plate 339 330 607 Zz
130 amplifier plate, compl. (new type) 339 330 709 Z
131 intermediate transformer 339 315 614 K
132 power plate, compl. 339 335 606 Zz
132 power plate, compl. (new type) 339 335 703 Zz
Continued from Page 7
The VU-Meter Circuit
A capacitor (C 127 / C 227) is connected via a diode (D101 /
D201) to the output (C124/C224) of each amplifier. The
negative half-cycles of the AF output voltage cause the diode
to conduct, so that the capacitor rapidly charges via the low
forward resistance of the diode to the peak value of the AF
voltage. The resulting DC voltage causes a current to flow via
a preset resistor and the VU-meter to chassis. The discharge
time-constant of the circuit is about 2.5 seconds and the charging
time-constant is about 0.15 seconds.
The Oscillator
The single-ended RF oscillator is switched on-for the recording
function by applying the supply voltage. The transistor T 107
operates in a grounded emitter circuit and employs inductive
positive feedback. The oscillation frequency is determined chiefly
a Item oo coe
133 oscillator coil 339 345 603 H
134 variable coil 339 345 604 G
135 ferrite core for pos. 134 339 450 604 P+
136 pot core 18x 14 for pos. 133 339 450 603 F
137 thermistor 47 Ohms 20% 339 530 005 F
138 twin ceramic trimmer B 15 / 80 N 1500 339 510 003 A
139 fuse M 0.4 C DIN 41 571 339 570 006 P+
140 fuse M 0.315 C DIN 41 571 339 570 005 P+
141. selenium rectifier B 30 C 1200/650 K 6 339 520 016 |
142 bulb fitting, compl. 339 560 005 D
143. miniature bulb 24V 80 mA 339 560 002 Cc
144 variable resistor 1 KOhms R 312/412/219 339505 707 A
145 variable resistor 10 KOhms R 102/103/203 339505 703 B
147 variable resistor 50 KOhms R 151/251 339 505 702 B
149 electrolytic capacitor
100 uF 15/18 V ins. C 124/224 339 584 032 A
150 electrolytic capacitor
1800 uF 25 V ins. C 302 339 588 001 |
151 electrolytic capacitor
1000 uF 25 V C 306/406 339 586 018 L
152. electrolytic capacitor
100 uF 15/18 V C 103
153 electrolytic capacitor
100 wF 35/4 V C 129
154 electrolytic capacitor
250 uF 6/8 V C 121/221
155 electrolytic capacitor
250 uF 15/18 V C 118/304/404
157 electrolytic capacitor
10 wF 15/18 V C 102/202
158 electrolytic capacitor
25 uF 10/12 V C 117/217
159 electrolytic capacitor
25 uF 15/18 V C 303/403
160 electrolytic capacitor
25 uF 25/30 V C 501
161 electrolytic capacitor
50 uF 3/4 V C 127/227
162 electrolytic capacitor
50 uF 6/8 V C 107/207
163 electrolytic capacitor
100 uF 3/4V C 112/119/212/219
164 electrolytic capacitor
5000 uF 35 V ins. C 402
165 diode OA 150D 101/201
339 584 026 B
339 584 017 Cc
339 586 002 A
339 586 003 B
339 582 006 A
339 582 010 Cc
339 582 015 A
339 582 016 B
339 584 013 D
339 584 012 A
339 584 028 A
339 588 004 M
339 527 002 A
by the inductance of the coil L103, the inductance of the erase
head and the capacitance of C 131. The different loadings of the
oscillator for mono or stereo operation due to the erase heads
are compensated by connecting a resistor R10 or a capacitor
C1. The bias voltage is fed to the record/playback heads via
the trimmers (C 12 / C 22).
End Switch-Off
The switching foil at the start and end of the tape closes the
charging circuit of an electrolytic capacitor (C 501) via the tape
end contact (S 8). The electrolytic capacitor lies in the base
circuit of an npn transistor which is thus made to conduct and
energise the stop solenoid for the duration of the charging
process. For renewed actuation of the stop function, the charging
circuit must first be broken again, so that the electrolytic capa-
citor can discharge through R 501.