Denon TU-M100 (c. 1996)
The Denon TU-M100 is a late-1990s FM/AM stereo tuner built to display FM character multiplex broadcasting. That was the Japanese "visible radio" teletext system, which sent text and program information in the gaps between FM audio signals. It was introduced around 1996 at ¥69,800, at the tail end of that technology's life. One Japanese repair blogger called it an "endangered species" today.
The big feature is a 2.5-line × 15-character graphic-type LCD. It can show program information, station names (registered using letters, numbers, and symbols), and the time. Page memory holds up to 150 pages, and a redisplay function pages back through 20 previously viewed screens. Network station search functions find affiliate or satellite stations. It also handles AM stereo, which some stations in Japan were still broadcasting at the time. The front panel carries the "DARC" logo, for the Data Radio Channel system used for FM teletext.
Inside, the TU-M100 is essentially the same as Denon's mini-component tuner, the TU-7.5L. A teardown by the Japanese blog BLUESS Laboratory found a small Mitsumi front-end package, two ceramic filters feeding an LA1265 IF chip, and an LA3401 VCO stereo decoder with no adjustment means for separation. Measured separation came in at approximately 25dB, well below the 43dB spec. The AM stereo decode IC appears to be a TA2040AP, though no datasheet was found. The board has only two adjustment points: T103 (FM reception) and VR101 (muting). The same blogger documented a common failure. The FM tuning point drifts out of alignment and stereo reception disappears. Adjusting T103 brought it back. The blog's comments include a 2011 thank-you from a reader who revived his own unit the same way, and a 2022 comment from an owner still using his TU-M100 daily, though the LCD dots are dropping out and the frequency is hard to read. Replacement LCDs aren't available as generic parts. Transplanting one from a junked unit is the likely only option.
The remaining specs are well documented. The FM section covers 76-90 MHz (the Japanese FM band) with a practical sensitivity of 12.8dBf, a frequency characteristic of 20 Hz - 15 kHz (+0.5/ - 1.5 dB), S/N of 77dB stereo / 82dB mono, and THD of 0.4% stereo at 90% modulation / 0.3% mono at 100%. The AM section covers 522-1629 kHz with 18 μV practical sensitivity. There are 40 station presets (8 buttons × 5 banks via a SHIFT key). The unit draws 9W, measures 434 × 75 × 238 mm, and weighs 2.6kg. A multi-function infrared remote (RC-803) was included, running on two AA batteries.
FM teletext broadcasting in Japan has since ended, so the TU-M100's marquee feature is now largely a historical curiosity. What remains is a compact tuner with AM stereo capability and a display that, as one owner noted, still shows frequency and stereo/mono status, as long as the LCD dots hold up.
- FM/AM stereo tuner with FM character multiplex (DARC) teletext display
- 2.5-line × 15-character graphic LCD; 150-page memory; 40 presets
- FM: 76–90 MHz, 12.8dBf sensitivity, 77dB stereo S/N
- AM: 522–1629 kHz, 18 μV sensitivity, AM stereo capable
- ¥69,800 (c. 1996); 434 × 75 × 238 mm; 2.6kg
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