This vintage original HP Model 400L Vacuum Tube Voltmeter operates and is in reasonably good cosmetic condition (main blemish is several numbers written on top and side of case). When tested with a 2.00 V sine wave, the meter readings were within +/- 5% at frequencies from 400 Hz to 1.0 MHz, except for 1 kHz, where there was a 10% error. Readings got worse at lower frequencies: 1.3 V at 100 Hz and 0.87 V at 50 Hz. Lower voltages and other ranges sometimes had much larger errors. Readings toward the low end of a range fail to register.

Since the instrument is not in proper working condition, it is being sold "for parts or not working". This vintage instrument is sold in "as is" condition and no guarantees of continuing operation are given. No returns.