Digital Synthesizer Tuner
1981
DEM 799,-
The medium-sized tuner of the Silver Series includes a feature even not present in the larger RT300: a digital timer/clock, allowing to turn the tuner plus two other devices on and off at preselected times. A single point of time and a daily-repeating time may be programmed. The tuner is never really off: the power switch is in reality only a key that instructs the microprocessor to turn the relay for the outlets and the tuner section off; the display then switches to a 24-hour time display. Since there are only five digits available, the time display doesn't include the seconds.
In contrast to the RT300 and MT1, the other digital tuners in the Silver Line, the RT200 does not allow entering a frequeny via the numeric keys. Note that '16 program memory places' means 8*FM and 8*AM; you can't have more places in one range and less in the other!
(taken from the user's manual and the service manual; I took the values from the service manual in case of contradictions)
| FM Receiver | |
|---|---|
| Wave Band: | 87.5 - 108 MHz |
| Circuits: | 11, 4 adjustable |
| Sensitivity: | 0.8 µV / 2.6 µV Mono/Stereo |
| at 26 dB at 75 Ohms | |
| 1.6 µV / 5.2 µV Mono/Stereo | |
| at 26 dB at 300 Ohms | |
| Limit Range: | <1.0 µV for -3 dB at 75 Ohms |
| Intermediate Frequency: | 10.7 MHz |
| IF Bandwidth: | 160 kHz |
| Selection: | 65 dB (2 signal method) |
| Mirror Selection: | >=70 dB |
| Capture Ratio: | <1 dB |
| Phase Suppression: | >55 dB |
| Carrier Signal Suppr.: | >70 dB |
| Frequency Response: | 10 Hz - 16.0 kHz |
| Distortion Factor: | <0.5 % stereo |
| <0.3 % mono | |
| at 1 kHz and 40 kHz deviation | |
| Cross Talk Dampening: | >38 dB at 1 kHz |
| >30 dB at 12.5 kHz | |
| Voltage Ratio: | >62 dB stereo (eff) |
| >65 dB mono | |
| S/N Ratio: | >64 dB stereo |
| >67 dB mono | |
| Range of Strength Display: | 1 µV - 2 mV |
| Accuracy of Standards: | 0 digit for station frequency in 50 kHz steps |
| AM Receiver | |
| Wave Band: | MW 522 - 1611 kHz |
| Sensitivity: | 9 µV at 600 kHz |
| (at 1 kHz 30% Modulation) | |
| Circuits: | 6, 2 adjustable |
| Intermediate Frequency: | 450 kHz |
| IF Bandwidth: | 4.8 kHz |
| Voltage Ratio: | 36 dB at U = 1 mV, |
| Accuracy of Standards: | +/- 1 digit |
| Range of Strength Display: | 8 µV - 5 mV |
| Frequency step: | 9 kHz |
| General | |
| Components: | 13 Integrated Circuits |
| 42 Transistors | |
| 43 Diodes, 20 LEDs | |
| Mains Connection: | 220 V |
| Fuses: | 1 x T 2.5 A (primary) |
| 1 x T 630 mA | |
| 1 x T 100 mA | |
| Dimensions: | 435 x 56 x 250 mm |
| Weight: | ~ 4.5 kg |
The RT200 contains a 4.8V NiCd accumulator pack. This is needed to keep the processor and the clock running while the device is disconnected from the mains supply (as I noted above, the microprocessor and its supply is still on when you turn the tuner off). During normal operation, the accumulator will be recharged. However, there is no protection against driving the accumulator into deep discharge when the tuner is disconnected from power for a longer period of time. Similar to the accumulators on older PC mainboards, this will (1) destroy the NiCas and (2) make them leak! If you see a pack with the white, crystal-looking electrolyte leaked out, immediately replace it, since the acid can also destroy traces on the PCB. The cells used in the pack have a non-standard size. Simply use a pack of four standard AA/R6 cells and connect it via some inches of wire to the PCB. Even the smallest AA cells available these days have four times the capacity of the original cells, and there is plenty of space in the case to install the new pack somewhere.
Out of Tune
The second next common failure is a synthesizer crystal out of tune. This becomes notable by the tuner's exact-tuning display: though the correct frequency for a certain station is set, the exact-tuning indicator does not 'show green'. Typically, it will claim a mistune towards lower frequencies. Since the tuning principle is a PLL synthesizer with a closed loop, aging of analog components like the varicaps or OpAmps is out of question, the synthesizer's reference clock must be wrong - just by a couple ppm, but enough...
You may try swapping the crystal, but since you will need to readjust the oscillator anyway, you may try to get the old one back to the correct frequency: the crystal is stabilized with two small ceramic capacitors. Their purpose is to assure a correct start and a stable oscillation, and they also have the property of slightly reducing the crystals resonance frequency. They are located between the crystals's contacts and ground. Try reducing their values (one of them is adjustable, but that is usually not enough) or unsolder them. For example, I had an RT200 that came 'back into tune' after I removed C272...
Linked to the out-of-tune phenomenon is the tuner's incaopability to reliably receive in stereo; an RT200 going mono in the music's rhythm is not uncommon ;-)
Failed +5V Supply
In case the tuner starts acting 'funny' or the display stays dark altogether, it's worth to check the +5V supply of the microprocessor. If it is more than half a volt too low, try to swap the regulating transistor for the +5V supply, T236. Seems this transistor is slightly underdimensioned and may get 'cooked' over time. I usually replace it with a BD135 plus a small heatsink.
Broken Processor
Another failure I had so far was a broken microprocessor (which is a complete project on its own, see below), but this is surely not a standard failure and more due to incompetent handling/repair of the previous owner...
(taken from Telefunken's 1981-1991 Service Handbook and the Service Manual)
| ICs, Transistors, Diodes | ||
|---|---|---|
| IC201 | IC TA7060 AP | 339 575 227 |
| IC202 | IC HA12412 | 339 575 228 |
| IC203 | IC LB1450 | 339 575 278 |
| IC204 | IC LA1245 | 339 575 285 |
| IC205 | IC LB1426 | 339 575 279 |
| IC206 | IC TCA4500A | 339 575 284 |
| IC207 | IC NJM4558D | 339 575 087 |
| IC208 | IC MN6147 | 339 575 281 |
| IC209 | IC MN1455LF (IC209) | 339 575 280 |
| IC210 | IC MC1741 (IC210) | 339 575 123 |
| IC211 | IC MB74LS42 (IC211) | 339 575 282 |
| IC212 | IC NJM7812A (IC212) | 339 575 283 |
| transistor BF451 | 339 556 289 | |
| transistor BC639 | 309 001 313 | |
| T204-207,209,224,228, | transistor 2SC1815Y | 339 556 292 |
| 229,231,233,234,237, | ||
| 238 | ||
| T201 | transistor 2SC380 | 339 556 052 |
| T202 | transistor 2SK212D | 339 556 453 |
| T203 | transistor 2SK212C | 339 556 454 |
| T208-225,210-223,227, | transistor 2SA1015 | 339 556 216 |
| 230,232 | ||
| T235 | transistor 2SA1020 | 339 556 456 |
| T236 | transistor 2SD592 | 339 556 455 |
| T101 | transistor 3SK45B | 339 556 456 |
| T102,104 | transistor 2SC535B | 339 005 901 |
| T103 | transistor 2SC461B | 339 005 925 |
| D201-204,207,208 | diode 1S446 | 309 327 925 |
| D205,206 | diode KV1225 | 339 529 322 |
| D209-214,217,220-223, | diode 1S1555 | 339 529 017 |
| 304,305,501-504,506) | ||
| D215,216,218,224,225, | diode SR1K | 339 529 101 |
| 229,230,303 | ||
| D219 | diode KB262 | 339 529 092 |
| D226 | diode DBA10B | 339 529 368 |
| D227 | diode 05Z7,5X | 339 529 317 |
| D228 | diode 05Z6,8Z | 339 529 318 |
| D301,302 | diode 05Z16X | 339 529 319 |
| D101-104 | diode 1SV53F2 | 339 529 314 |
| D105 | diode 1S2687C | 339 529 315 |
| D520,522,523 | LED SR531D | 339 529 323 |
| D521 | LED SG231D | 339 529 320 |
| D524-528 | LED LN05202P | 339 529 321 |
| D503 | LED SLP135B | 339 529 324 |
| rectifier | 339 520 051 | |
| Filters | ||
| FL201,202 | low-pass filter | 339 368 014 |
| CF201 | ceramic filter 10.7MHz | 339 367 116 |
| CF202 | ceramic filter 10.7MHz | 339 368 016 |
| CF204,205 | ceramic filter | 339 367 132 |
| L201 | coil 10.7MHz (L201) | 339 347 039 |
| L202 | lowpass filter 195 kHz | 339 367 117 |
| L203 | choke coil 2.2µH | 339 348 655 |
| L204 | coil 3.3mH | 339 347 045 |
| choke coil 220µH | 339 347 038 | |
| L206 | antenna coil | 339 347 139 |
| L207 | oscillator coil 100µH | 339 347 138 |
| L208 | coil | 339 367 114 |
| L209 | coil | 339 367 115 |
| L210,211 | choke coil 39µH | 339 347 040 |
| symmetrical transformer | 339 312 114 | |
| L101 | coil | 339 347 134 |
| L102,104 | coil | 339 347 135 |
| L105 | coil | 339 347 136 |
| L108 | oscillator coil | 339 347 143 |
| L106 | coil | 339 347 137 |
| L107 | coil | 339 367 113 |
| Misc. Electrical Parts | ||
| accumulator 4.8V | 339 283 128 | |
| key | 339 442 121 | |
| mains button w. rod | 339 202 109 | |
| push button | 339 222 132 | |
| push button | 339 222 124 | |
| push button, 2 fold | 339 222 125 | |
| push button, 3 fold | 339 222 126 | |
| tuning knob | 339 222 123 | |
| J201 | antenna socket | 309 670 928 |
| J202 | DIN socket, 5 poles | 339 540 114 |
| J203 | cinch socket | 339 540 146 |
| FLU201 | digital display | 339 335 108 |
| FU201 | fuse T2.5A | 309 627 916 |
| FU202,203 | fuse T400mA | 339 572 004 |
| FU204 | fuse T100mA | 339 570 023 |
| R220,267 | var. res. 10KOhm | 339 508 651 |
| R246,279,286 | var. res. 20KOhm | 339 508 653 |
| R355 | var. res. 5KOhm | 339 502 015 |
| RY201 | relay | 339 360 108 |
| S201 | push button assembly | 339 442 119 |
| XTAL201 | crystal 4.5MHz | 339 349 154 |
| battery 4.8V/150mAh | 339 168 006 | |
| FM mixer board | 339 337 145 | |
| C101,109,112 | trimmer | 339 510 061 |
| C124 | trimmer | 339 510 062 |
| station buttons board, cpl. | 339 337 137 | |
| tact switch w/o diode | 339 442 020 | |
| tact switch w. diode | 339 442 018 | |
| scanning board, cpl. | 339 442 130 | |
| key assembly for it | 339 442 120 | |
| mains socket | 339 480 107 | |
| mains switch | 339 442 121 | |
| mains transformer | 339 312 112 | |
| mains cable | 339 480 106 | |
| Misc. Mechanical Parts | ||
| cable binder | 339 911 713 | |
| front plate, cpl. | 339 132 128 | |
| side part f. front plate | 339 232 125 | |
| frame f. tuning knob | 339 222 145 | |
| button frame | 339 222 144 | |
| buttons guiding, 8 fold | 339 222 143 | |
| indicator window | 339 272 128 | |
| display frame | 339 337 142 | |
| push button holder | 339 917 111 | |
| push button spring | 339 917 110 | |
| housing, upper part | 339 112 107 | |
| housing, rear panel | 339 137 110 | |
| foot | 339 062 112 |
Replacing a broken microprocessor
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