R-390A anyone know what this is?

[k7iou]

Bought a R-390A Navy (63) Imperial and this strange device on the terminal strip. Trying to diagnose no receive and if I disconnect this Carrier meter drops to 0.
See picture. The relay below Dow Key is a receiver mute
Regards
de k7iou

[WBear2GCR]

looks to my eye like someone potted a small relay with epoxy in an ice cube tray!

Maybe it's plastic resin, not epoxy.

Best guess.

                _-_-

[W2VW]

Probably a 600 ohm to spkr xfmr fb.

[MikeKE0ZUinkcmo]

Maybe an "improvement" of the SSB AGC??  I have a 390 in the refurb Queue, and have documentation, but haven't cracked the book open yet, so I know nothing specific about the 390 AGC, nor even looked at any schematics of same, so this is just a wild guess.

PS,
Sorry for the confusion, my first post was way out in left field.   I saw the word "line" and with out looking further, presumed that to be AC power, and answered accordingly.   Then, after Posting it, I saw "VWs" comment, looked at the pic again, and quickly changed my post to the above, then after posting THAT, I see your second post.  How embarrassing.    

[k7iou]

From R-390 forum:
SSB "enhancer" module.  Here's a description from the list archives --
Subject: [R-390] RE: usb/lsb Tune Aid
The thing from Radiofinder is not worth much. The basic idea is a bridge rectifier connected
to the audio, and that is filtered and run into the AGC. You use the line audio control to
control how much audio goes into it, and listen on the local audio. So it gets you some audio dervied
AGC which is a good way to get AGC for SSB reception; and it knocks down the
RF gain some so that the BFO has a chance of demodulating the SSB signal with less
distortion. But it doesn't work very well; the best thing that can be said for it is that it
requires no internal mods to the receiver..

[k7iou]

I did find this, I could not copy on my iPhone so I snapped a picture.
http://www.r-390a.net/Pearls/SSB_conversion.pdf
I will disconnect it and try the receiver again. Maybe the bridge rectifier went belly up and is causing QRM?

[MikeKE0ZUinkcmo]

Interesting, thank you for the information.   When my receiver gets its turn on the bench I'll have to get busy reading that, and all the other stuff I've accumulated.  

[WD8BIL]

No receive is probably because there is no jumper connecting 14 and 15. (diode load)

[k7iou]

No receive is probably because there is no jumper connecting 14 and 15. (diode load)

Getting the picture now.
Previous owner performed an audio mod.
When I got it the 500k pot wasn't here so I dug thru my junk and temporally added one. I didn't add the capacitor and there is a white wire disconnected from where the Navy diode load was in the front panel. The white wire is a center conductor in a shielded wire.
Please see his modification. This fellow is well known for his audio mods and a well know restorer uses them in his 75A4 restorations.
I have a spare audio module I'm trying to clean up but I don't know as of yet if he modified anything else that would preclude me from swapping it out.

[k7iou]

A friend educated in schematics said it was a straight forward audio mod as I was uncertain if the previous owner modified something elsewhere. He said also I need the jumper so I installed it. I now have speaker audio, RF gain but still no receive. Does the Navy shielded lead for the front panel diode load socket need to be connected?
See picture.