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Another from Ranger RCI-X9

The receive static is typical RCI / Galaxy also. Thankfully it is remedied in the same way. Adjust L8, this one took one full turn to the right. I assume this is the normal L8 can at the output of the double fet stage. It seemed to work the same way but I haven't found a print to verify.

The turn or twist - is subjective. In some feedback experiences I've had retuning the Galaxy L8 and L6 mess - the detune of the FET-side for the less "noise" effect, tends to make some weak signals "peak in - with in - the noise level" much like how the sound tracker works - the speaker is quiet until the signal "breaks-in" then the noise level is mixed in.

Some people don't like the results while others don't mind and feel the quiescent result of the detune helps to hear the signals they want to hear and not the swooshing of AGC that tends to compress the audio and the noise level present - together.

"To rant a little more-:"
I remember in the older CB Tricks days, the Galaxy series of radios came out with the "twin-FET" amp design. Many thought of it as a "savior" while others, like myself - dreaded it.

As others are now experiencing - the noise levels - even in ambient no-signal presence. There are now many newer noise sources we have yet to fully understand and decipher how they get in there, the older single FET and even the Bipolar designs (think TRC-427) of IF strip - gave the radio a sort of warm tone to both signal to noise level as well as tonal performance in how the AGC and the detectors worked together to develop a sound similar to a much larger system without the expense - as well as the ability to push down the noise floor because the engineering of the strip took into account the quiescent current in the bias for that stage as needed to keep the semiconductors from injecting their own noise.

We seem to have lost that art...
 
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I'm still on a base station huatus but finally the rci-x9 returns today from Superior cb.

A really nice woman called to update me Monday and said it was now completely aligned and ready to talk. He had to replace some parts and did some update mods and should be all squared away. Eventually will get to try it out and decide if it's a keeper.
 
Gentleman I'm in need of some help with one of these. I had one of these donated for parts because I already had one. It had multiple components toasted but before dismantling it I wanted to give it a shot.

So I'm now to the point of setting bias on the rt1's. My first time working on one of these with double rt1 pre-drivers to drive a single rt1 final before it goes into the amp.

How do I go about the bias on this monster?

The amp I can set no problem but this radio is a new one to me.
 
I did it by putting a current meter in line with the radio's main power. Needs to be the 20 Amp range, pretty much. Setting bias will call for turning the bias trimpot for minimum current with the mike gain at zero keyed in either sideband mode. The trimpot will place zero bias current on that transistor at this end of its travel. Now key the mike and advance the trimpot for the additional bias current you want over and above the reading with zero bias. Unless you're a sideband fanatic, 10 mA is safer than the traditional 40 mA. Was on the 2995 radios, so RCI told us.

A differential measurement. They didn't give us a test point to interrupt the drain circuits and insert a meter in a proper way.

But setting the trimpot for the difference, starting at the trimpot's zero-bias end of travel is how we set bias for the 4 and 8 IR520 amplifiers. No way to break the drain circuits on those boards, either.

The manufacturer/importers don't want you to revive a failed unit, so the means to do it has to be hacked.

73
 
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