My Telefunken Collection

RT 300

Photo of RT 300's Front
Photo of RT 300's Back
Photo of RT 300's Innards

Device Type

Digital Synthesizer Tuner

Start of Sale


General Description

The RT 300 is the largest and most luxurious tuner of Telefunken's 1981 lineup. It offers almost all features one would have expected for a good tuner at that, with the notable exception of the timer functionality found in the RT 200, and the analog tuning wheel found in the TT 750. It can however still be regarded as a direct successor of the TT 750, since the digital tuning system is almost the same, built around three chips custom-made for Telefunken.

The RT 300 was part of Telefunken's T 300 high-end component system, and it has a remote control input that allows the drive functions to be controlled via the RP 300 pre-amplifier.


FM/MW/LW, 40 program memory places, manual/automatic tuning, digital frequency input, LED field strength indicator, exact tuning indicator, fluorescent display, automatic muting via RP 300


FM antenna (both dipole and coaxial), AM antenna, AF out(DIN and Cinch), Remote Control

Technical Data

(currently no documentation available)

Common Failures

Photo of RT 300's
Power Supply Section

Selen-based rectifiers were still commonplace in Telefunken devices at that time. Though it is generally known that such rectifiers have a finite lifetime, the B30C400 in the RT 300 is an especially sad story; from the five RT 300s I own, three had a broken rectifier when I received them, and on another one, the rectifier blew within the first hour of operation - immediately detectable by the disgusting smell of selen and sulfur. It is therefore my advise that whenever you get an RT 300, immediately replace the rectifier with a newer silicon-based one, regardless whether the original one still works or not! I have a device where a fried rectifier led to a failure in the power supply section and killed the custom-specific ICs in the digital tuning section. And opposed to a simple rectifier, these ICs are irreplacable these days :-(

The rectifier is a red, rectangular-shaped component between the regulator's copper heatsink and the large filter capacitors. The photo shows a sample of the rectifier left to the board, the rectifier has already been replaced in this unit. Finding a silicom-based replacement shouldn't be a problem, a rating of 40 volts and 300 milliamps is not very high for a silicon rectifier. The pinout will probably not fit 100%, but there is enough space to bend the wires appropriately.

Photo of RT 300's
Digital Tuning Section

Another problem is shared with the TT 750: dried-out capacitors in the digital tuning section. It consists of two boards held together by a metal frame, and there is few chance for the heat to escape from the section. Furthermore, a small light bulb is used as a current limiter, and this bulb burns from time to time...

Spare Part Numbers

(taken from Telefunken's 1981-1991 service handbook)

ICs, Transistors, Diodes
Position Order No. Designation
309 368 312 microprocessor DFC103
IC 170 309 368 133 IC TDA 1046
IC 704 309 368 283 IC LM 324
IC 707 309 368 311 microprocessor DFC103A
IC 709 309 368 240 IC ER 1400, DIL case
IC 703 309 368 284 IC CA 3080 E
T 700/701 309 001 933 transistor BF 241
GR 501 309 320 928 rectifier B 30 C 400 A
D 717 309 325 114 diode BZX 85 C 6 V 8
Miscellaneous Parts
Position Order No. Designation
309 395 040 LED display, 10-fold

Available Documents

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©2002 Alfred Arnold,