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GALAXY SATURN NO RECIEVE

Discussion in 'CB and Export Equipment and Accessories' started by BAGEBOY, May 25, 2021.

  1. BAGEBOY

    BAGEBOY Member

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    I hear only strong signals. They give 2 or 3 db The speaker is not quiet..I can hear them talking

     
    #16 BAGEBOY, May 28, 2021
    Last edited: May 29, 2021

  2. nomadradio

    nomadradio Analog Retentive

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    I think you said that turning down the RF Gain won't change the signals that are loud enough to hear.

    This should mean it's time to test TR17, the first RF amplifier transistor. The RF Gain control connectes pretty directly to TR17 and nothing else.

    And if turning down the RF Gain DOES still reduce the sensitivity, TR17 seems less likely.

    73
     
  3. BAGEBOY

    BAGEBOY Member

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    I tested tr17 and it checked fine.i also replaced it just to be sure still no luck. I saw a thread to change L12 I tried that.. also Where should I check now
     
    #18 BAGEBOY, May 29, 2021
    Last edited: May 30, 2021
  4. nomadradio

    nomadradio Analog Retentive

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    So, refresh my memory. Does turning the RF gain control cause a signal that you CAN hear to change in any way? When you have a signal strong enough to hear, of course.

    And that's another thing I didn't think to ask. Do you have a source of a steady receiver signal, like a signal generator? Hard to troubleshoot a receiver without a test signal that stays the same while you're changing things in the radio.

    73
     
    NZ8N likes this.
  5. BAGEBOY

    BAGEBOY Member

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    The signals I can hear are like 2-3db and shifting. The rf gain doesn't change the signal.
    Unfortunately I don't have a signal generator. so I am a bit stuck..I
     
  6. Handy Andy

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

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    There are several directions you can go here...

    So I'll start simple.

    The TR17 - you said it had a 2SC2999 - so did you change it back to a 2SC1674?

    The basic premise here, is to get this thing back to "stock" and then figure out the problem(s) from there...
     
    NZ8N and kaos513 like this.
  7. BAGEBOY

    BAGEBOY Member

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    I change it ba k to stock.i check tr18 I also check d15 and d16 I can hear my near by stations but 2-3 dbs and even if I try to vary using the rf gain control it makes no change.
     
  8. Handy Andy

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

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    Ok, thanks! I will work on the side here...

    So you know, when RF gain doesn't go up or down - it controls TR17 yes, but if they did any mods to that section, this may turn into being something much harder to track down - trying to put in a different part - if left stock - won't give you much change.
    • TR17 is changed, back to stock, but no change when you turn RF gain.
    • Gotta' verify that RF gain - uses 8 volts, at the pot, and the other side goes to board ground - the wiper adjusts - absorbs - power from TR17 - it flows from the RX 8 volt receive to ground thru TR17 - but uses the RF Gain pot for "ground"
    • Before it get's there, it goes thru a section designed to limit the amount of signal arriving to it. That's the purposes of D15 and D16 - so if you trust your work on this - so far so good.
    • So if RF gain has no control - Check it and verify that it can raise and lower it's wiper arm from 8 volts to zero volts thru it's range - so that means you 'll have to lift the wire up off the board or just pull a part - R66 - a 1K (Brown - Black - Red) - doing that - opens the circuit to L6/TR17 - stops the flow of power from the RF gain knob - one leg of that R66 is simply unsoldered, lifted up - and verify the RF gain control knob, when turned - that wiper arm is between 7.8V to 0.1V thru it's range - tested with DVM Positive lead on R66 line to RF gain knob across to ground.
    • R190 is a 1.5K (Brown - Green - Red) that powers (sources) RF Gain control from the 8Volts RX side. It's done this way so it don't blow up the pot or the circuit from too much current.
    • So if you don't get voltage, that's adjustable - there's part of your problem
    • If you HAVE a voltage and it doesn't adjust - look for open Pot Substrate opened up, and or open part R65 - a 1K (Brown - Black - Red) - they may have changed it or removed it to make the 2SC2999 work


    So to me this may be something more of, they tried to do more receive mods to the radio - and gave up, then you're left holding the bag.

    So my best advice I can give, is to go to CB Tricks Website and locate a Galaxy 88 or 77 board and try to reconstruct the section part by part, just verify parts to their parts lists - I know the part numbering will be different, but they kept a lot of the parts IN THE SAME PLACE - you just have to put the pieces of the puzzle back one piece - or part - at a time.

    I'm sure they didn't do the whole section, you just have to reconstruct the section back to the original platform.

    Once enough of the pieces are put back in their place, the puzzle becomes much more clearer.

    The radio works, just not very well. But it works. So take your time and study what Bennie did up for CB Tricks, if anything - the site was done for a person like you. Anyone, needing help to put back together and keep their equipment working.
     
    #23 Handy Andy, May 31, 2021
    Last edited: May 31, 2021
  9. BAGEBOY

    BAGEBOY Member

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    Thanks Andy
    But I must say the radio was receiving all along I had some challenges with the output which was due ton a final that was sorted out.i took up the radio and it was receiving as I had skip 30db then it just went down and it came up by the time I was able to check it was back down ad all I could hear was loud stations 2-3 dB all that was done was a decal was added to the face ...originally I was saying may be it was moisture from applying the decal but the was t any water on the knobs etc
     
    Handy Andy likes this.
  10. BAGEBOY

    BAGEBOY Member

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  11. Handy Andy

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

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    Got that! Ok, then if you want to keep the 2SC2999 - it sounds like RF gain control doesn't have any voltage to change the output of TR17.

    TR17, is more of a "common Base Amplifier" - it isn't an amplifier by voltage, it's thru current.

    So how does that happen?
    upload_2021-6-1_11-26-32.png

    It's Collector - sources power all the time from the RX 8 volts.

    The amplification occurs when you have the greatest differences in potential across the Collector to Emitter it's voltage drop.

    You don't have any change...

    So you lost your RF gain control - either at the pot or in the TRACE leading to it.
     
    #26 Handy Andy, Jun 1, 2021
    Last edited: Jun 1, 2021
    NZ8N likes this.
  12. Handy Andy

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

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    Why you only have 2 to 3 S-units (dB's) is from the R66 and R65 combination - there is enough voltage drop across these two parts to get some signal thru - it demonstrates that the section works, but no adjustment means open line - AFTER these two parts, but BEFORE the RF Gain control.
     
  13. Handy Andy

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

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    This is for a EPT3600-13 or 11Z board...

    If I caught your PM, you have the 14B board...

    • Conversions...
    • R65 may not exist...
    • "#57" is common tie point for SQ and RF Gain - TIES TOGETHER - BOARD Ground
    • C133 is used to "quiet" the trimming slide scratch the RF control can add - in Earlier boards they used a simple Disc cap of 103 or 473 value (0.01uF to 0.047uF) (C47 or C48) will have one leg on the TRACE that is to the RF Gain Wiper ARM (Variable)

    Locate your RF gain knob, and R65 and R66 - they should share a common trace.

    One side of R65 will head to foil ground - R66 will cause a "break" in the foil (Series circuit) and continue to head off to L6.

    Once you've located them both, Check R66's Resistor lead that is on the Continuous foil trace away from L6 towards the front of the board - nothing else is in it's way back to RF Gains' WIPER leg.

    You do a continuity check between those two points.

    You may not "hit" RF gain control Wiper arm leg right off the bat (usually it's the Center) but as you "back probe" to find the correct leg - as part of your continuity check, you'll see ohmic readings - some may show low ohmic, other will be O.L. or Flashing 1 (infinite) so check to make sure your Ohmmeter settings on your DVM is for 1X - not 10X or 100X or any above that. You need to check for a DEAD SHORT.

    After checking all the RF Gain legs, and you still have not found your DEAD SHORT, make sure you're checking the LEG of R66 that should be towards RF Gain and the Front panel.

    • When you look at RF Gain control
    • - you can easily see the wiper arm and the two other legs, wires should be soldered to them
      • This is that controls wiring - your color code
      • - locate the pot, check across it's legs to see if any TWO of them are constant
      • - usually the pot is 1K (so you'll need to reset DVM Ohmmeter to 10X or 100X setting) and verify the Pot does measure it's RATED (stamped value 102 or thereabouts) ohmic reading
      • - TWO legs should be the highest ohmic value closest to 1K (1,000 Ohms) while the other "parings" will be less than this.
      • Sooner or later you'll find the WIPER Arm
        • - because the other TWO are constant
        • - when you Test these legs, one will be variable to the other two
        • - lesser in ohmic measured value - this one is your WIPER - that wire soldered to it - is the Color code of the one buried into the front part of the board in it's LOOM.
        • See those "numbers" in the schematic above?
        • #57 is Foil Board Ground.
        • #56 is WIPER (or at least should be)
        • #55 IS 8 Volt RX constant
      • Locate Header at MAIN PCB
      • Locate R66
      • C333? BY TR1 towards Centerline and IC1
        • C333 can be removed as needed replace as per CONVERSIONS with a value similar to C47 or C48 shown above
    upload_2021-6-1_19-29-47.png
    Gotta stop here and make dinner - will pick up in another post.
     
  14. BAGEBOY

    BAGEBOY Member

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    My board is Ept3600-14b no r65..I am seeing 8v at the wiper is that correct
     
    #29 BAGEBOY, Jun 2, 2021
    Last edited: Jun 2, 2021
  15. Handy Andy

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

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    Heed my advice about CONVERSIONS, so yes, no 65.

    Wiper has 8V - too much.

    Should be adjustable - really shold not be higher than 7.2 V and goes as low as 0.1V (Foil Ground)

    If Wiper doesn't change - your RFG pot is open - no connection to Foil Ground. You have to check it.

    So review the work, SQ and RF Gain share common Ground Tie.

    You need to Check RF Gain pot out of circuit to verify it's bad. Else if it's NOT bad, as in you have Variable between BOTH Constants One sides ohmic reading rises as the other side falls, as you turn the knob - if you can verify the Ohms and Wiper is working - you'll need to verify the Circuit.

    • I need to point out something here...
    • Locate your Head - should be LOCATE YOUR HEADER FOR THE POT - goes INTO the board...

    shieesh...

    If Squelch is adjustable, yet RF Gain is not, then Replace RF Gain pot.
     
    #30 Handy Andy, Jun 2, 2021
    Last edited: Jun 2, 2021

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