PACO Z-80 Audio-RF Signal Tracer
Overview
PACO's Z-80 is a classic audio + RF signal tracer for tube-era radio and TV servicing (manual dated 1957, cataloged ~1960). PACO was the kit-line brand of the Precision Apparatus Company (Glendale, Long Island NY; later Pacotronics, then part of Dynascan) — sold both as a kit and factory-wired. A probe feeds an internal high-gain amplifier with a 1×–1000× attenuator, whose output drives a 5-inch PM speaker and a 1629 magic-eye indicator tube in parallel. Five tubes: 12AV6, 12AU6, 12AQ5, 12X4 (rectifier), 1629 (magic eye), plus a germanium diode in the RF demod probe; 117 V AC mains. Beyond tracing, it offers output-transformer/speaker-substitution terminals, an AC wattmeter (load outlet), and noise/input testing. Workflow: probe stage by stage from the front end — where the trace dies is the broken stage.
Context
Signal tracing is the dual workflow to signal injection (where you inject at successive stages and listen at the speaker output). For tube-era receiver service, the two techniques together localize almost any signal-path fault in minutes — far faster than trying to brute-force-trace voltages against the schematic. PACO and Eico were the two big names in budget signal-tracer kits of the era; the Z-80 is the higher-end PACO unit. Common service issues: the electrolytics in the audio amp, the speaker cone, and the probe cables (rubber sheaths get brittle and short).
