AVO 8 Circuit and Components

The AVO 8 uses some very specialist coils and components, many not readily found today. Most of the resistors and capacitors are replaceable with conventional components; however, the moving coil movement is irreplaceable. Many of the coils are un-obtainable as well. I just recently bought a meter on eBay with dishwasher salt in the coils! The salt was shorting the coils; however, I managed to get my friend Rufus to re-wind new replacement coils. Many of the "Panclimatic" resistors are wire wound and they are difficult to find as well, however, there is always some old stock on eBay going cheap.

Rectifier Repair

The rectifier is the component, which converts an AC current to a DC one. If your meter can no longer measure AC currents and voltages, then this is the component to check. My friend Rufus had one with a faulty rectifier and he repaired it with an ordinary bridge rectifier! Heavy peak currents can sometimes puncture the semiconductor-based rectifier, as it is impossible for the mechanical cutout system to react fast enough to protect it. Hence, AVO instruments manufactured after 1954 were fitted with a surge suppression rectifier across the main rectifier to provide protection.

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