I have had some success in repairing the old .Royal tachs, though some of the components are not longer available. For example, if the meter or range switch are gone, there are no replacements available and the whole thing is kaput! What will you take for your DOA tach, shipped to 92704., it might have some good parts.
I have the complete original RCM article, schematics and even with Kinko's elevated copy prices, copies are available should you have a local tech willing to tackle it There are no similar tachs available that I know of, except for a "TNC" which is quite pricey. The digitals have problems. First of all, the engines themselves seldom hold a steady RPM at max throttle, and the tach doesn't either. The resulting reading changes so much it is not even possible to get an average reading.. Luck,
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