FM-3 EMM801 not indicating

When I turned my system on today, the FM-3 indicator would not respond. The "Stereo" lights up and the strength bars are there, but they do not move when the dial is turned. It sounds just as good as ever, so before I open it up, can anyone tell me if I should be looking at another tube that sends the signal to the EMM801. Fortunately, I have a spare EMM801. Just wanted to save a step of installing the new indicator only to open up again to test other tube(s).
Denny, I hope you see this - you've been a great help in the past with FM-3 questions.

Since your FM-3 is otherwise functioning properly:

With the tuner turned on and connected to an antenna so you can receive stations, check the voltage at Pin 9 of the EMM801 dual eye tube, or at eyelet 29 on PC-8, with a digital voltmeter or VTVM.  If it does not vary in the range between approx. -0.1VDC and -9VDC as you tune stations in and out (NOTE: more or less, but a NEGATIVE voltage), replace R19 and C21 on PC-8 and check associated solder connections on PC-8.

If this looks proper, check for approx. 150 volts DC at Pin 8 of the EMM801 eye tube.  If you don't get it, look for a bad R20 and check related solder connections on PC-8.

Problem solved! I took the lazy way out - swapped the EMM801 for another, with no change to the indicator. I pulled the tuner and checked all the tubes. One aside - the original Mullard EZ80/6V4 is still going strong; no wonder everyone wants Mullard rectifiers! In checking I found one 6AU6 shorted and a 6BL8 was weak. Fired it up and everything is fine!