icom r-71a

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icom r-71a

Post by sprman on Wed Feb 04, 2009 7:45 pm

Hi my icom r-71a has bad distortion on LSB.The AM,USB,CW,FM all work fine.Anyone ever seen this befor?Sprmam : [

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Re: icom r-71a

Post by exray on Wed Feb 04, 2009 8:39 pm

This might not apply to your r-71 but I had a IC-745 which is of the same genre. Although the 745 covered 'all' bands it was actually split internally over something like 5 or 6 bands. Each 'band' had its own bandpass filters, etc and had individual oscillators. You just didn't *know* that by tuning around.
The crystal oscillator on one of the bands went wonky on me and everything on that particular band (about 5 MHz wide) had a warbly sound. A simple tweak of the trimmer fixed it.

I point out this example because maybe the ' band' that you are suffering from the most just so happens to be where you use LSB the most. I forget exactly how the LSB/USB are set up in the Icom but it could also be that side of the beat oscillator just needs a tweak. I seem to recall that USB and CW used the same local oscillator and LSB was the odd man out. FM and AM would not use a beat oscillator at all. RTTY was a third oscillator.

So compare it across a bunch of widespread freqs and see if the LSB distortion occurs all over. If its the same all over I'd suggest checking that LSB oscillator's frequency to see if it has ' jumped' out of whack.
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Re: icom r-71a

Post by sprman on Wed Feb 04, 2009 10:17 pm

Hummm i have service manual and just now a looking at it some.The band is 80 meters and 160 meters. This R-71a was moded by EEB now out of buissness.Has better filters,audio mods and low noisepre-amp and spike protection.Was burned in 24 hrs and aglinment was rechecked.Has 2.1 kc filter and 2.8khz and 4khz filters.Was bought new in 5-9-88 by my brother.Got it playing now and it sounds ok ,but will wait and see.Could be a heat problem ,after 5 to 10 mins it goes into distortion.Sprman : )

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