I've had a search for rev counter issues, and while there is a lot of information, hints and tips out there, I haven't found a complete troubleshooting guide to try to narrow down the problem.
I've had a problem with my rev counter, and have been trying to fix it using the age old 'stab in the dark' technique, applying the different (valid) suggestions in previous posts. So far it hasn't worked, so I've tried to apply some analysis to what the symptoms are, and what should be checked, in what order (i.e. there's no point investigating the condition of the earth connections if the rev counter needle is missing and the MFA LCD is cracked!)
There are a lot of assumptions in this, based on my own limited technical knowledge, and from other suggestions picked up on here, and not all of it will be right. However, if this is a tool that will be useful for people trying to diagnose their rev counter problems, then any suggestions to improve its accuracy would be appreciated.
Once it is right, I've thought about adding photos, diagrams and links to other 'how to' threads in the diagram where relevant.
http://i716.photobucket.com/albums/ww165/tony_ack/revcounterdiagnosis.jpg