Galaxy SSB Echo Base - no modulation

[Hawkeye351]

Hmmm,

Soldered only the orange wire (8v) to the potentiometer = 8.59v, with gain up or down.

Soldered only orange wire (8v) to its outer pin and the light grey wire (goes to R65) to the wiper pin of potentiometer = 3.61v with gain all the way down and 5.17v with gain all the way up. Hmmm...

Soldered only orange wire (8v) to its outer pin and the black wire (gnd) to its outer pin of potentiometer = 3.64v with gain all the way down and 3.65v with gain all the way up.

Solder all three wires back to their respective legs of potentiometer = 1.59v with gain all the way down and 2.2v with gain all the way up.

In one way I can see it as a bad pot being shorted somehow, but then again I can see it as something downstream of the wiper wire is shorted straight to ground.

Strange...

 

[Dr. Frankenstein]

I was using the 99v schematic where I saw the C333 cap.
I pulled out one of my radios which has the same circuit as the 99v to read the following.

With the RF Gain turned full Clock Wise (CW) you should have close to if not 0 volts on the wiper.
With the RF Gain turned full Counter Clock Wise (CCW) you should have close to 2.2 volts on the wiper.

If you have a scope, now is the time to see where the receive drops out, starting at L6 (which you said you replaced) and going towards L12 and then possibly beyond.

Here is the voltage chart for the transistors right from CB Tricks for the 99v being very close to what you have:

Galaxy Radios DX99V Service Manual

Now it's up to you to find the problem since the RF Gain circuit seems to be working right.

Good luck and don't give up.......

 

[Hawkeye351]

I did notice the audio would scratch and pop, sometimes drop completely out when I start adjusting any of the IF cans in that section. If it goes out then I can just barely tap one of those cans and it comes back as it has been. The only ones that do that when adjusting (gently) are L7, L8, L10, L11, L12.

If I try to gently adjust any of those above, then is when it starts the scratchy noise and popping, sometimes it drops completely out, til I gently tap on any of the above.

It's as though one of those IF cans internal caps has come loose. None of the other cans does that. 2 of the above IF cans slugs (L7, L10) are almost flush with the top of the can. That's where I get the most receive, still low though.

I'll check the trans in that circuit and go from there.

How do you check these IF cans in circuit?

 

[nomadradio]

Would a potentiometer that measures the proper resistance drop an 8v supply down to 2.2v upon connecting to said pot?

Depends on where the wiper is positioned.

The "black" Galaxy base stations from the late 80s/early 90s had a higher-than-average failure rate from front-panel controls. Generic catalog replacement pots usually had a shaft that was just too short. Finding replacements with a split 6mm shaft the same length was a wild goose chase at times.

This may have nothing to do with your symptom, but this generation of black radio would show up with one or more bad controls way more often that average for other base radios.

73