[R-390] Detector tests followup

[Flowertime01 at wmconnect.com]

Barry, ask the following question.

One interesting thing about the BFO.  With it off, there is very, very 
little no-signal noise.  With it on, the no-signal noise jumps up 
dramatically.  Don't know what this has to do with anything but thought I'd 
mention it.  It's one of the main things that made me start trying to 
diagnose this deck.

_______________________
So first off most of the receiver is disconnected so we expect a low noise 
level.
When the receiver is working well we still think we have good tubes and 
expect a low noise level. We do not hear a lot of the noise from the from the IF 
deck because it is not at audio frequencies. We detect the modulation on any 
signal in the IF deck. Most of the noise is of constant amplitude and has little 
if any modulation to detect.

Once the BFO is turned on then we hear more audio output. The noise is of 
amplitude but of different frequencies. as the "random" noise mixes with the BFO 
it produces more "snap crackle pop" at audio frequencies. 

Pretty much a normal response.

Look what happens when you inject 455 into the IF. You expect -7 volts on the 
diode load. You ad modulation and you get -7 volts on the diode load but 1/2 
watt of audio output.

You turn on the BFO and you peg the -7 volts off the meter scale.

The BFO mixes with the noise and you get a lot more out of the audio.

BFO levels vary with every tube. So no one has tried to characterize how much 
change is possible or meaningful.

Some is there and that good.


Have you got the distortion out?
Is the receiver sounding good?
Is MGC giving stronger audio signal than AGC?
Are you getting a good 1/2 watt output with the TS585?
Both line and local audio channels?
When you get a 1/2 watt out on the line with the TS585 and back the line gain 
down to read 100 Milliwatt Zero DB on the TS585 does the VU line meter read 0 
VU?

Roger AI4NI