measuring quieting sensitivity to determine how well your front end is aligned at those frequencies.
Rick,
Here are the results of the test you asked me to perform.
I'm assuming I performed them correctly.....
I am displaying the output setting of my generator as it reads in dbu EMF.
I suck at converting db, dbu, dbu emf, dbm and anything else not mentioned......LOL!
No Ant input............AC Voltmeter reading......... .170 v
No modulation..............Start......... -20 dbu EMF............ .170
10 ............ .180
20 ............ .185
30 ............ .190
35 ............ .200
38 ............ .190
39 ............ .180
40 ............ .170
41 ............ .150
42 ............ .135
43 ............ .110
44 ............ .090
45 ............ .070
46 ............ .050
47 ............. .040
48 ............ .033
49 ............. .025
50 ............. .016
51 ............. .008
52 .............. .002
53 .............. NO NOISE FROM SPEAKER!
Not sure why there was an increase in voltage from 10 to 39 dbu EMF.
Attached is the spec sheet for this tuner.
I was able to get most of the alignment settings completed on my spare practice unit but am still having an issue with alignment procedures # 20 and 21 on the attached alignment sheet.
I used my Amber distortion meter for all other distortion readings and had no problem seeing the changes on the analog meter as I was adjusting the pots......as a matter of fact, most of the factory settings were dead on or very slightly off. But with procedure 20 and 21, I was not able to see any changes happen at all when adjusting the pots. Those procedures require me to feed a 10 khz into my generator which I did from the Amber and read for distortion but could not see any changes no matter what configurations I tried.
I did make sure I had the generator set for external input and was clearly able to to see the 10 khz signal at the audio output of my tuner on my scope. The generator selector was also set for MAIN and L as per the procedure.
I do have another generator that I had tried using to feed the generator with but had the same results. At first I thought perhaps the other generator output signal might have to high a distortion level which was not allowing me to see any changes when adjusting the pots but like I said, even the Amber generator is giving me the same results so I'm confused.
Update!..........
I looked over the attached schematic for the distortion cancelling circuit board where all of the distortion alignment pots are located.
Alignment # 20 and 21 pots are located on the lower left hand corner and each adjust the input of both halves of IC 15 .
So this is what I tried......I turned off the power and connected a test lead to pin 7 of the chip and connected to the distortion meter and tried once again to adjust VR 9 and was able too see great changes to the analog meter of the distortion meter. I set the pot for the lowest distortion level and it brought me to almost identical factory setting so I'm guessing I must be on to something.
I then did the same thing for pin 1 and VR 8 and I had the same results!
So my question is.......am I actually reading distortion and is it ok to do it like this?
And why the heck couldn't I get the same results at the audio output just like the rest of the distortion readings from that circuit board without having to go right to the chip pin out?