Grundig TK 850

The Grundig TK 850 (also known as TK 850 Hi-Fi FM or TK 850 FM in some documentation) is a high-end, solid-state open-reel (reel-to-reel) tape recorder and integrated FM receiver produced by Grundig Radio-Vertrieb in Fürth, Germany. Manufactured primarily from 1974 to 1976 (peak production around 1975), it was a premium consumer stereo model aimed at audiophiles and serious home users who wanted a self-contained hi-fi system with tape recording capabilities. It combined a quarter-track stereo tape deck with a built-in FM tuner, stereo amplifier, and dual loudspeakers, all in a compact, low-profile cabinet with smoked glass lid and carrying handle.

The TK 850 was priced originally around 1,000–1,200 DM (a high-end consumer figure, equivalent to roughly £100–150 in export markets), positioning it as one of Grundig's most advanced combination units in the early-to-mid 1970s. It gained collector interest for its forward-thinking design (integrated FM stereo receiver with tape deck), clean solid-state performance, and versatility as a complete audio center, though it was not a pure professional deck.

Key Technical Specifications

Track System: 4-track (quarter-track), 2-channel stereo / monaural (stereo record/playback; monaural operation also supported; records on one quarter-track per pass, allowing four tracks total on standard tape by flipping reels twice)

• Tape Speeds: Three speeds — 4.75 cm/s (1⅞ ips), 9.5 cm/s (3¾ ips), and 19 cm/s (7½ ips); switch-selectable (higher speed for high-fidelity music, lower for extended runtime)

• Reel Size: Maximum 18 cm (7 inches); commonly used with 13–18 cm reels; supports standard NAB/international hubs

• Heads: 3 heads — separate erase, record, and playback (permalloy construction; allows real-time off-tape monitoring during recording, a key hi-fi feature)

• Motors: 1 motor (capstan drive; single synchronous motor with mechanical reel assistance; high-quality design typical of mid-1970s premium consumer machines)

• Drive System: Mechanical transport with push-button controls; constant tape speed; foil-sensing automatic stop at tape end; advanced tension regulation suitable for standard and thinner tapes; additional features include automatic/manual recording modes, input mixing, sound-on-sound overdubbing, and built-in twin amplifiers

• Frequency Response (all ±3 dB):30 Hz – 20 kHz at 7½ ips
  30 Hz – 15 kHz at 3¾ ips
  30 Hz – 8 kHz at 1⅞ ips (excellent for the era, especially at 7½ ips; meets high-fidelity standards with wide bandwidth and good extension)
  

• Signal-to-Noise Ratio: Better than 55–60 dB (weighted; excellent for mid-1970s consumer stereo, aided by separate playback head and low-noise solid-state circuitry)

• Wow & Flutter: Less than 0.08–0.12% at 7½ ips; less than 0.15% at 3¾ ips (outstanding for domestic use; among the lowest figures in Grundig's late lineup, thanks to synchronous motor and precise drive)

• Equalization: IEC/CCIR/European standard for the period (some export versions note NARTB compatibility)

• Inputs:Microphone: Low-level (two inputs; dynamic mic via DIN or proprietary socket; often supplied external mics)
  Line/Radio: High-level via DIN connector (Grundig 5-pin standard)
  Phono/Grammophon: Additional high-level input for record players
  

• Outputs: Built-in loudspeakers (two integrated high-flux elliptical permanent-magnet dynamic type, fed by 26 W total stereo amplifier); low-impedance ext. speaker; high-impedance line out (stereo preamp output for external amplifiers) via DIN socket; output power 26 watts total (internal stereo amp)

• Power Supply: Alternating Current (AC) mains — 110–240 V (multi-voltage taps for export); power consumption around 60–90 W; no battery option (mains-only domestic/portable hybrid)

• Dimensions: Approximately 510 × 160 × 420 mm / 20.1 × 6.3 × 16.5 inches (W × H × D) — compact low-profile table model with smoked glass hood and carrying handle

• Weight: Approximately 12–15 kg / 26–33 lbs — substantial due to metal chassis, 3-head assembly, integrated FM tuner, and stereo amplifiers

• Electronics: Fully solid-state (transistor-based; 71 transistors reported in some sources, including output stages; no tubes, marking Grundig's shift to transistorization in hi-fi models)

• Other Features: Integrated FM tuner (FM broadcast band only, with station keys); recording level indicator (VU meters or glow type); mechanical tape counter; automatic tape-end stop; pause function; input mixing; sound-on-sound overdubbing; tone control; recording time up to 8–16 hours total (depending on speed, tape thickness, and track usage) on 7-inch reels with long-play tape

Design and Performance Notes

The TK 850 was a forward-thinking combination unit with a focus on hi-fi fidelity and convenience: quarter-track stereo allowed two stereo tracks (or four mono tracks by flipping), doubling capacity compared to half-track designs. Dual (or three) speeds provided flexibility—7½ ips for near-professional music fidelity (wide bandwidth, excellent transients), 3¾ ips for balanced domestic use, and 1⅞ ips for maximum runtime on speech/dictation. The three-head design enabled real-time off-tape monitoring during recording, a significant upgrade over 2-head models. The integrated FM tuner and 26 W stereo amplifier with two loudspeakers made it a complete audio center. The solid-state electronics delivered clean, dynamic stereo sound with superior clarity and imaging—modern vintage ratings place it around 7–8/10 for sound (one of the finest combination Grundig recorders of the 1970s) and 7–8/10 for build reliability/durability.

The drive mechanism was robust and precise (single motor, belt drive), with additional features like mixing, sound-on-sound, and FM reception enhancing everyday use. Common long-term service needs include:

• Cleaning heads, capstan, pinch roller, and tape path

• Replacing rubber drive belts/idlers (common failure point in 1970s solid-state models)

• Replacing electrolytic capacitors (leakage common after 50+ years)

• Lubricating mechanisms

• Checking transistor stages and power supply

Historical Context

The TK 850 was part of Grundig's late TK series that transitioned toward solid-state hi-fi combination units with integrated FM tuners and stereo capability. It followed earlier stereo models like the TK 244/TK 247 and preceded Grundig's full shift to cassette dominance (e.g., C-series). Surviving examples are highly sought-after by collectors today, often prized for their outstanding audio performance and condition due to robust construction, but most require basic restoration (especially rubber drive components and capacitors) for reliable operation. They represent a high point in vintage solid-state open-reel collecting, especially for those interested in mid-1970s German audio engineering and all-in-one DIN-compliant quarter-track stereo designs with three-head monitoring and FM tuner.