[R-390] Still wondering about the 100mV detector test

[Flowertime01 at wmconnect.com]

Barry,

You are OK.

Love Boston and Ayer Mass. Fort Devens is now a gated upscale community.
There is a prison over on the Shirley gate end of the post.


TM 11-5820-358-35 page 37 para 25. Line Audio Channel.

"The maximum audio power output available at TB103 terminals 10 and 13 is at 
least 10 milliwatt's."  You report 15.

10 milliwatt's is +1 VU

I see some of the other things you added about the switch in +10 and reading 
+2.
How ever I think things are crowed up on that end of the meter. I think you 
are doing OK.

VU   Dbm    Volts             Power
 0       0       0.775 volts      0.001 watt
+1    10       2.449 volts      0.010 watt
+2    20       7.740 volts      0.100 watt
+3    30     24.494 volts      1.000 watt

The 5 200 ohm resistors in the H pad toss 490 milliwatt up in heat.
There is a meter circuit in your R390.
The designers knew you would hang a meter on the back panel.
The designers knew the transformer existed.
The designers knew the 200 ohm H pad was going into the circuit.
The designers selected meter resistor values to deal with all these problems.

What the VU meter reads and what is on the terminals of T602 do not agree.
What the VU meter reads and what is on the terminal board TB103 terminals do 
agree.
Keep your fingers outside the box.



I rewired my audio deck as follows
Remove the terminal board TB103 jumper between pins 11 and 12.
Move the wire on T602 pin 4 to pin 3
Mover the wire on T602 pin 5 to pin 6
Add a jumper on T602 from pin 4 to pin 5.

You now get a 1/2 watt out on pins 11 and 12.
Pins 10 and 13 act just like they always have.


Roger AI4NI