R-390A Carrier Level Meter reading?

[WBear2GCR]

Trying to make my #2 R-390A percolate.

It's up and running. But the Carrier Level reads rather low.
Can't at this point find any bad parts or tubes...
Seems to be receiving normally... no sign of overload (AGC works).

Wondering what your R-390A shows with the CAL signal on the meter?
What's the DC voltage on the back side between ground and the AGC jumper at the
same time? The bands will vary, but maybe at 3.900mc would be a good
reference frequency?

Any ideas or experience with the same symptom(s).

Thanks in advance...

                  _-_-bear

[WB4YVO]

My R390A  a EAC Sn 399 reads at 3.9 mhz a 40 on DB scale..4kc Bandwidth. BFO off

Cannot get to back of unit as its in a cabinet.

Skip

[WD8KDG]

bear,

The carrier level meter sits between V506A & V504. Where that old meter needle rest depends on the condition of both tubes and their respective circuits. In the years I've played with the R390/A, odd readings of the carrier meter was the result of a failing tube. In general; a 20DB reading on my R390/A's is about a S9 on a YaeComWood. These comparisons are usually on the 75 meter AM segment.

Cal signal readings vary band to band. I like to believe DB on a R390/A means "dog biscuit". Down load the Y2K R3 manual and find in the later chapters the "how to" measure the Signal plus noise vs noise ratio. Using that method a 20:1 ratio means you are there, not much else left to do. But if'n you have a warehouse full of tubes go for the 30:1 holy grail.


Craig,

[WBear2GCR]

Turns out I was re-inventing the wheel!!

Problem is/was that the stock meter has a 17ohm internal DC resistance.
The 1ma movement that is/was in the radio has a 100ohm internal DC resistance.
Won't work.
This is laid out in a compendium of emails from the old listerve over a period of about 15 years!

Radio works fine - wrong meter!

I think I have a solution to the "wrong meter" issue in general.
One fellow made an opamp based meter driver many years back, mounts on a PCB behind the meter.
I think I can make it simpler by using a differential pair as a simple current amplifier... either that or
a pair of jfets...

                              _-_-bear