Digital FM Stereo Tuner AJ-1510

• alternative name: Heath Company

The Heathkit AJ-1510 (and its successor, the AJ-1510A) is a landmark in high-fidelity history, recognized as one of the first digital frequency-synthesized FM stereo tuners introduced in the early 1970s. Unlike standard tuners of its time, it featured a keypad for direct frequency entry and no tuning knobs. 

Technical Specifications:
According to a May 1972 review in Audio Magazine, the AJ-1510 was a high-performance unit with the following specifications: Sensitivity (IHF): Less than 1.8 µV. Selectivity: Greater than 95 dB (alternate channel). Distortion: Harmonic distortion is rated at less than 0.3%. Frequency Accuracy: Better than ±0.005%. Dimensions: 16 3/8" Wide x 6" High x 14 3/4" Deep. Weight: Net weight of approximately 15.75 lbs. 

Key Features:
Digital Interface: Tuning is performed via a 10-key keyboard, auto-scanning, or specialized pre-programmed punch cards. 
Memory Cards: The unit includes three slots for plastic "programming cards" that allow users to save favorite stations by cutting notches into the cards to represent frequencies in Binary-Coded Decimal (BCD). 
Display Technology: The original frequency readout uses four RCA Numitron incandescent tubes, which glow behind a green filter. 
Internal Build: It utilizes a pulse-counter detector for low distortion and features two five-pole IF filters for high selectivity. 

Maintenance & Modern Upgrades:
Because of its age and the early digital technology used, certain components often require attention:
Display Failures: The original Numitron tubes are fragile and now difficult to source. Modern LED display replacement kits, such as the AJA-1510-1 from Heathkit, are available to replace these tubes with more reliable LEDs. 
Restoration Kits: Complete recap and restoration kits are frequently sold on sites like eBay to address aging electrolytic capacitors and other drifting components. 
Programming Cards: For those missing the original station-select cards, reproduction programming cards can be found through vintage electronics specialists. 

Kit AJ-1510, Tuner less cabinet, 23 Ibs., mailable $539.95 USD.
AJA-1510-1 , Pecan cabinet, 6 Ibs., mailable. $24.95 USD.

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