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Very nice work. Seems like the radio came out great.

Sounds kind of similar to an issue I'm having with my 138xlr. I just haven't had a chance to probe around in it yet.

I ended up just wiring in a variable by removing vr13 because I was pressed for time. I did get a tip though that I'm going to use for next time. That is to change r237 to higher value to keep carrier from going to high when variable is wide open. Which is really my main concern.

Good info there unit 75. I'm going to be messing around with this and will post back with results.

Isn't there a way to do it with leaving vr13 intact? I mean it's the same board as the other radios that have variable rf power from the factory. Anyone ever do it a different way? Thanks

Yea I know the hakko is supposed to be really nice. Out of my price range though.

Any good desoldering vacuum guns that are stand alone? I'm starting to get sick of using so much braid. Don't mean to hijack just curious.

Bump

If I run my wires straight from the vr13 location to the potentiometer control knob, do I run the risk of burning out the pot? I want to try this on a ss3900 by using the swr variable control. I thought I read somewhere about putting a resistor somewhere inline? Thanks

Pm sent to you nomad

If I wanted to use the ch. 9 switch on the front for a hi/low, what do you do with the wires currently attached to it? Can they just be removed? Thanks

So if I was to use the spectrum analyzer to do the bias for clean output and linearity; I'm assuming adjust for lowest reading on 2nd harmonic should work? Or just look for any spurs around the fundamental? Thanks

Thanks for the detailed response blasphemy000. So let's say I want to bias my dual final radio for class ab operation. According to what I read that means the transistor will be conducting between 180 and 360 degrees of a cycle. How do you go about doing that? How to see it on the oscilloscope...

So on a dual final mosfet radio for example I can just put my dmm to the amps setting and adjust bias for lowest draw on each mosfet? This is the better way to do it? Thanks

Check c155 its a very small 1pf cap. It may be cut or missing.

Yep I have all the info from unit 399's old page downloaded. Thanks

Bumping this thread, because I am experiencing same issue original poster had. Driver bias sets fine but final bias won't go higher than 25ma or so. Maybe my radio is one that had the factory 15ma final bias? I have to look into that service bulliten.

Thanks LC, I appreciate that tip. I'll definitely be giving it a try.

I have an 8 digit b&k so should be ok. I already tried the mini amp as well didn't see a difference maybe I got a bad one. Which hp counter do you have kaos?

Anyone ever have an issue picking up the 10.695 etc frequencies when doing alignment?