Trouble getting RPM reading on Aerovee

[LarryEWaiex121]

Working on a second hand Onex retirement project. Going well except for no RPM indication. Here is the back story so please read before replying.
I have the older legacy MGL Stratomaster 3 1/4" instrument. I also recently installed the same instrument but in the 2 1/4" size primarily for more temp inputs in my setup for EGT's.
Back to the RPM issue. I'm not getting a reading on the Stratomaster with the Sonex factory recommended setup.
I'm pulling signal off of right tab on Reg/rectifier. Per Kerry, I switched the AC leads off the alternator and left the signal wire on the right tab. That resulted in weird reading of 180-240 range. Instrument is set for range of 3500 RPM. No combination gets a reading.
I went back and wired in the new smaller FF-1 engine moniter and same thing. No reading.
Pulse is set to 6 pulse per factory again. I've tried 5 and up to 8. No help.
Now I'm thinking possibly its a Reg/Rectifier issue or the Stator itself?
Again, more back story. I've put my Deltron trickle on the Odessey battery and it always tops at 12.6 volts. I'm used to my lithium battery in my Waiex and it shows 13.3 at rest and under load with Camit alternator it cruises at 14.1 volts at low load (no strobes or position lights) and down to about 13.9 volts with everything going including auto pilot servos and seat heater.
On engine startup I'm showing 12.4 V at 2200RPm and 12.6V at rest. Gradually the voltage is dropping to about 12.1 after about 5 minutes of run time at various RPM's. Including up to 2700 on ground.
What is most likely culprit? Regulator/Rectifier or Stator? How does one check output with engine running? Safely.
I have one of those Tiny Tachs I wrapped around a plug lead and it works quite well. Just not interested in operating a plane with a $15 tach.
Additionally, I've checked my input wiring all the way back to the D sub pin and there is continuity. Not getting something on one instrument is a possibility and reasonable. Not getting anything on either is a stretch.
Any recommendation would be appreciated. I'm homing in on the no charge aspect because to me this seems most likely based on voltage readings.
Thanks, Larry

[Bryan Cotton]

Larry, you covered all the right things I think. Charging issues seem like a possibility. I don't get good charging until I'm flying though, although good enough to give me RPM above 500 or so.

[Panther16]

Disconnect stator output leads and connect ac volt meter to leads and run leads into cabin. Run eng and a good stator will show 30-35 volts ac at hi power. If ok down to regulator if wiring is correct.

[LarryEWaiex121]

Thank you Panther. That is the kind of helpful info I was seeking.
I built my Waiex and not a single electrical glitch in 13 years. Buying someone else dream and sorting things out is a way bigger challenge. Truth be known, I did take this project on as a retirement project to take something not quite ready for prime time and totally sort it out. I'm getting there.

[LarryEWaiex121]

Well in the end, I went back and did the most basic thing one could do. Hadn't dawned on me till I had a beer to contemplate this matter.
I used my voltmeter to do a basic continuity test on the alternator. Nothing. That lead to pulling the stator/ignition plate off the back of the engine. Then it was obvious. Allen head machine screws had backed out of the trigger post and chewed a 1/4" ring in the stator. Destroyed.
After pulling off the trigger shaft, it had marks on the backside of it and the screws that hold the magnet ring to the flywheel had backed out. What a disaster.
I went on the Sonex Service Bulletin site and first thing I found was the screw issue. My screws were the 3/4" instead of the recommended 7/8". Plus there was no sign of any type of locktite. Waiting for parts.
Mystery solved why no rpm and also why seemingly no charge. Because the alternator was toast.