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Galaxy saturn problem - meter readings

Discussion in 'CB and Export Equipment and Accessories' started by jrd426, Jan 13, 2019.

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  1. jrd426

    jrd426 New Member

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    Hi guys, I'm hoping someone can help me with a problem I have with a old galaxy saturn base. The signal meter when switched to sideband is way to sensitive and off the charts. If I reduce the rf gain it corrects the problem. AM signal meter reading with rf gain up is fine. Any thoughts on how to correct? Another meter I put in does same thing.
    Many thanks!


     

  2. nomadradio

    nomadradio Analog Retentive

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    Pretty sure VR1 sets the S-meter for AM and FM. VR2 sets it for SSB. Sounds as if someone has randomly cranked VR2.

    Normally you feed a fixed level of receiver signal to the radio, like 50 uV and set the meter for S9.

    If the trimpot has oxidized and gone bad, it may refuse to turn down.

    73
     
    Shadetree Mechanic likes this.
  3. jrd426

    jrd426 New Member

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    Thanks for the message Nomad. I tried to turn down vr2 with not much result. It knocked it back from vibrating off the scale to just solid off the scale. I wonder if the trim pot is shot. Other then this signal meter flying off the scale on ssb the radio seems to work great other then a high pitched noise coming from the frequency counter enclosure.
    Wondering now if I should plan to replace vr2 trimmer
    Many thanks
     
    RT431 likes this.
  4. Handy Andy

    Handy Andy Do Your Research First, Then Decide...

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    Wow!

    When you have to trim VR2 AND RF gain, you may need a little more TLC around the AGC side of things for SSB modes.

    IF you encounter problems with adjusting VR2 - then maybe you should look at IC1 and the AGC side of it.

    Does your IC 1 look like this?
    GalaxyAGCIC1.jpg

    AGC in AM may work, but if SSB AGC is bad, you get symptoms like the above because it seem like it acts like too much or not enough - and everything sounds distorted.

    So look over he parts boxed in Green, AM is red, so if you can see if you get power to SSB (Green) to help AGC action. So you see that AGC accepts power from the MODE selector...
    GalaxyAGCIC1AMSSB.jpg

    Hope this helps!
     
    #4 Handy Andy, Jan 14, 2019
    Last edited: Jan 14, 2019
  5. jrd426

    jrd426 New Member

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    Thanks Andy for the message. My ic-1 is different.
     

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  6. Handy Andy

    Handy Andy Do Your Research First, Then Decide...

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    The schematic will apply - look at the R274 - 270 K same spot - so boards are nearly identical so all you need to do is locate the AM cap, then close by is the SSB cap C31 - Schematically it's a 47uF - but considering the age of that radio - it may have failed - it dried out - older electrolytic's turn into "dead shorts" when they do.

    So it may bear to mention that you may have other quirks that will crop up on the older chassis like the Saturn - because of the quality of the Electrolytic Caps - their construction - will make them vulnerable to drying out.

    So if you have a spare moment and a soldering iron and can work on it- may be worth to try and see if the cap C31 can be swapped out for another - or at least testing it with the DVM and see if R49 obtains a voltage from the SSB MODE feed - should show between 8V on resistor to about 3.3 V on the base of TR12.

    TR 12 would have a signal on it from the AGC feed the VR1 and VR2 use from the AM and FM Detector as well as the SSB conversion of what's at TP6 C34 rectified and sent to IC1. So a direct DC check may not reveal anything - just easier to swap out the caps.

    Caps themselves change the "Rate" of Attack and Decay of the AM and SSB signals that appear as a bias rectified from the detectors POWER it sees in the signals strength. It's processed and the out[put of Pin 14 of IC1 which basically tracks the PIN diode front end as attenuators. When SSB mode, the line affects where the attack and delay decay takes place on the feeder line to the IC1 input gate of that Quad Op amp Pin 12.

    Heres' a little help to narrow it down...
    GalaxyIC1C31C32.jpg

    On your radio - there these two...
    OnyourRadio.jpg

    Hope this helps!

    :+> Andy <+:
     
  7. jrd426

    jrd426 New Member

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    Wow Andy. You know these chassis's. Your tips are fantastic. I will try your suggestion and look at those caps and just replace them out. I cant thank you guys enough for your help and suggestions.
    Best Jeff
     
  8. Handy Andy

    Handy Andy Do Your Research First, Then Decide...

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    The Galaxy chassis is the most studied and like the IBM PC - the open architecture platform for radio out there.

    The more diverse, knowledgeable, other-wise just plain smart operators, whom are in radio - CB and Ham alike - use and abuse that chassis due to the Galaxy radios lines architecture being the way it is. They exploit the flaws, perks, Mods, Audio and AM regulation controls that allow for Direct Injection (Fidelity), Echo, Asymmetry mods - that can be developed - honed, sharpened and perfected - and as you can easily see - applied to nearly all the other radios of this genre.

    They can easily lay claim to being what they are, and having their progeny scattered in DNA "Fingerprints" throughout the entire radio lineage even into Ham radio.

    No matter what the demise of RCI or Galaxy as banes to the Radio Universe, they have brought many CB and Ham radio enthusiast alike, many hours of pleasure and fun - learning from this platform.
     
  9. jrd426

    jrd426 New Member

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    I guess they are what they are and agreed on the enjoyment many have had both using them and working with them. I will look for a good source to buy replacement caps of decent quality and take it from there I think. I have a few other similar that need to be all recapped as well. Many thanks for your time!
     

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