Westerbeke tach works, hour meter not

[Hoodsail]

I have a 1978 westerbeke w-30 (4 cyl), that has a tachometer that works well, but the hour meter, set within the tach (see pic), stopped moving about 1.5 seasons ago. I have searched the forum, looked in Calder's diesel book & Manley's "diesels afloat" book without finding any answers to my questions. My tach is driven by signal from alternator.
1. Does the tach drive the hour meter? If yes, then hour meter is broken and assume I must replace entire unit.
2. If hour meter gets signal from source other than tach, what is that source?
3. Can I assume that the entire unit is powered from just one source (see my pic of wiring attached)? So if I have power to tach, i should have power to meter.
New tach unit is about $300, so trying to determine if its fixable or not.
thanks