I just completed the whole Smaug mouth servo thing. Ken at JJP was great at helping me through it. I checked voltage on the Smaug Control Board J102 connector pins 1 & 3 when the mouth should be moving using the Smaug mouth min/max settings. These are the 3 pins where the mouth servo motor connects to the board. I set up a stand in the cabinet with the playfield raised to make it easier.
IMG_9391 (resized).jpeg
Here are the settings that I measured:
Min.
Setting, VDC
100, -.206
105, -.216
110, -.226
115, -.236
120, .247
Max.
Setting (Min. at 100)
120, -.246
115, -.235
110, -.224
105, -.213
100, -.202
These progressively inclining/declining numbers showed us that the control board was working but not the servo, so Ken sold me a new servo. The new servo worked and I followed the procedure in the manual to calibrate and mount the control horn. This didn't work for me at all so I pulled the horn off and did my own calibration: I set the min(mouth completely closed)/max(mouth completely open) settings in the middle of their range, selected the min setting, held Smaug's mouth almost all the way closed, and mounted the horn onto the servo (no screw yet). Then I went back and forth between the min & max adjustments to fine tune it by carefully pulling the horn off and rotating it 1 notch at a time then pushing it back on. When I got it close I put the screw in the horn and did final adjustments with the menu settings. Make sure that when the mouth is closed that you can't hear the servo still trying to move. If you can then back the min setting off until you don't hear it, plus a little more.