Galaxy dx-66 squeals on talkback

timspur, hi. First off, using the talkback with a tuned Galaxy will give you problems, so you need to use a good noise cancelling mic like a RK 56, or Astatic 636. If your running an amp, that will only amplify the problem. Here is a mod if your comfortable working on your radio, to tone down the TB volume.
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Talkback can become distorted if these radios have been "peaked," and there is no cure because the talkback just amplifies what goes to the RF section. Try adding a 470k ohm resistor from junction of C155/R207 to the junction of C187/R235 on the solder side of the board. This will also give you clean talkback on SSB and FM. Try different values of resistance to get the amount of volume you want. The less the resistance the louder the talkback will be.**
Hope this was what your looking for,, I know for a fact that the Astatic mics do help tone it down.
Let us know,,, Mechanic

Problem may be solved by several methods:

Re-install TR32.

Disable Talkback.

High SWR.

Antenna mounted such that RF is injected into the mic or mic cord.

TURN OFF THAT LEENYER.

I have "talkback" installed on three of my radios and all talkback is, is a resistor soldered onto the bottom of the board. All you have to do is CHANGE THE EXISTING RESISTOR TO A SMALLER RESISTANCE. I'm NOT a tech and can't say which one but if I was you, I'd take it to a repairman/tech and ask him what size he recommends. Or you can try a "variable talkback" that limits the volume. CHANGE THAT RESISTOR.....SHE'LL WORK "JUST FINE".

Disabling Talkback Disconnect wire located in J15 no more squeals