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Galaxy 99V No AM Carrier

Discussion in 'General CB Services Discussion' started by Mr. Fortyfive, Aug 29, 2011.

  1. Mr. Fortyfive

    Mr. Fortyfive Member

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    Hello everyone!!
    Got a older model 99V that don't have no AM carrier, but the radio still modulates and shows wattage on my watt meter. There's audio in the
    talkback and the audio sounds distorted and weak.

    I have replaced TR51, TR50, and TR49, also replaced some Elec. caps
    along the audio and modulation circuit, and did voltage checks on TR37
    TR38 and show normal reading and it does switch from RX to TX. TX
    indicator works and show it is transmitting.

    I also replaced the pre-driver, driver, and finals, but still no AM carrier.
    I don't know if something else is shorted out, like other caps, etc. :confused:
    would appreciate any advice and info, and Good Day to everyone. 73's



    Mr. Fortyfive
     
    #1
  2. loosecannon

    loosecannon break on through

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    do you have SSB transmit?
    if so, how many watts?

    are you able to adjust the bias on the driver and finals in SSB mode?

    when you say you have no AM carrier, but it will swing up with modulation, how many watts of "swing" do you have?

    does adjusting the RF POWER knob on the face of the radio have any effect at all?

    does adjusting VR16 or VR13 inside the radio have any effect at all?
    LC
     
    #2
  3. Mr. Fortyfive

    Mr. Fortyfive Member

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    Thanks for the reply!!
    sorry I took so long to answer back, just been busy.:mellow:

    I'm getting about 13 watts tops on USB, and 17 watts on LSB.
    and this is with RF Power on high.

    On AM, On Low Power, 1/2 watt DK with 16 watts swing,
    On Hi Power, 1 watt DK with 16 watts swing.

    VR13 and VR16 seem to be working and I did replace them and
    I'm able to adjust the DK to 1 watt with VR13 turn all the way
    up, and VR16 all the down with 1/2 watt DK.

    I wasn't able to get any bias reading for the driver and finals
    on SSB.
    But I do get readings on AM, but just for the driver (with no
    adjustments on VR11) also my meter can only read up to
    400 ma, but have a .52 amp reading on the 10A scale. But
    wasn't able to get any reading on TP7 for the finals (both
    VR10 and VR20)

    I did a quick test on the driver and finals by using the
    multimeter using the diode-test, and checking the base
    (pin 3) and seem to be getting normal reading, but that was
    just a quick test. So I'm sorta thinking that maybe the driver
    or one of the finals is not working right, but I don't know, but
    you know, I'm still learning.:p

    Mister-45
     
    #3
  4. loosecannon

    loosecannon break on through

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    it actually sounds like its working ok, but need you to do one more test first.

    the driver and finals are probably fine if you are getting that much wattage, but there can be a problem when both bias adjustments are not "in sync" on the dual finals.
    the radio will act like one of them is not there.
    that could be why you are not getting the full 25 watts of PEP watts when in SSB.
    your ability to only get 1 watt of deadkey would seem to indicate that this is not what is happening though.

    try adjusting VR13 and VR16 one more time but do it the way i show you here.
    (they work with eachother and adjusting one does affect the other)

    this should be done in AM mode in the normal CB band, channel 20.
    mic gain all the way down.

    first, turn the RF power knob all the way up.
    now adjust VR13 for max deadkey, but not more than 8 watts.
    if you still cant get more than about 1-3 watts deadkey, turn VR16 to its mid position, and check deadkey again.

    right now ill assume you were able to get a decent deadkey. if you werent, read further for a few more checks to do.
    now turn the RF power knob all the way down.
    adjust VR16 for 1 watt deadkey.
    now turn the RF power knob back up all the way and re-check your deadkey.
    if it need adjusting, turn VR13 to get the "max deadkey" that you want.

    this can take a bit of bouncing back and forth to get the wattage you want for max and minimum RF power knob setting.
    the thing is to have the RF power knob all the way up when you adjust VR13, and all the way down when you adjust VR16.

    as for the driver and final bias setting, your meter going to 400mA is just fine because you will only be measuring 50 to 100mA.
    lets make sure you are doing this right.
    remember that measuring current is not the same as measuring voltage.
    when measuring voltage, you put one lead to ground and one lead to the voltage point, which would be "parallel".
    when measuring current you put the meter leads in "series" with the wire/lead carrying the current.
    if you have ever set your meter to read mA and put one lead to ground and one to the Test Point, then you have probably blown the fuse in your meter and need to replace it.

    ok, to measure the bias current for the driver, set the radio to either USB or LSB, turn the mic gain all the way down, and remove the bias or "mirror" board.
    set your meter to read mA and connect the positive lead to TP9.
    to read the driver bias, connect the negative lead to TP8 (closer to the driver).
    now key the mic and read the bias current on the meter.
    adjust VR11 for 50mA.


    because your radio is a dual final radio, you have to do the bias reading a certain way.
    leave the positive lead on TP9 and move the negative lead to TP7 (closer to the finals)
    key the mic and turn VR10 all the way down as noted by seeing a reducing reading on your meter.
    now with the mic still keyed, turn VR20 all the way down, and you should see a reading of 0 mA on your meter.
    now adjust VR10 for 50mA, and then adjust VR20 to increase the reading to 100mA.
    replace the mirror board.

    if you werent able to get a decent deadkey on AM, measure the voltage on the mirror board in AM mode TX and tell me what that voltage is.
    (remember that since you are now measuring voltage, one lead goes to ground and one lead goes to the mirror board)

    good luck,
    LC
     
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  5. Mr. Fortyfive

    Mr. Fortyfive Member

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    OK, I did some adjustments on setting the DK, but I can get no more than
    1 watt DK. I have VR13 crank all the way up, and VR16 set half way. The
    RF PWR Knob, VR13, VR16 seems to be working OK.

    Still trying to set the Bias in the driver and finals, but so far, I'm getting
    no readings on TP7, and TP8 on SSB. But, I'm getting .52A on the 10A
    scale, Because my multimeter can only read up to 400ma, and I'm reading
    over 400ma on TP8, and this is on AM. And no measurements on TP7.

    I did check voltage on TP9 and I'm getting 7.13 Volts - Unkeyed, and 6.99
    volts - Keyed.

    So, I'll just keep checking different components, more head scratching,
    and see if we figure out whats going here, But appreciate the info.
    Good Day!!

    Mr. Fortyfive
     
    #5
  6. Robb

    Robb Yup

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    DRIVER BIAS:
    Band Switch & Ch. Selector to 26.965 MHz Ch.1 Band E
    Mode to USB
    MIC GAIN at minimum.
    Remove metering jumper (the 'mirror board')

    Connect DC Ammeter between TP9 and TP8.
    VR11: Key the mic/TX - adjust for 50-75mA.

    FINAL BIAS:
    Band Switch & Ch. Selector to 26.965 MHz Ch.1 Band E
    Mode to USB
    MIC GAIN at minimum.

    Connect DC Ammeter between TP9 and TP7.
    VR10 & VR20: First step is to key the mic/TX & adjust VR10 & VR20 for minimum (0mA) current.
    Next, key the mic and then adjust VR10 for 50mA.
    Then, key the mic and adjust VR20 for 100mA total.

    Put the 'mirror board' back in place.
    Done


    From:
    Galaxy Radios DX88HML Service Manual
    (same as a 99V)



    .54 amps on your driver bias reading is slightly more that half an amp - if I understand that you are on the 10 amp scale. You need to test for milliamps; which is a fraction of what you are reading now. You have the driver over-biased, if I understand your reading correctly.

    If you do not have the equipment to do these adjustments; then I strongly suggest that you send your radio to a reputable shop nearby and have them check out your radio and see if it doesn't need anything more than a complete alignment.

    ;)
     

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    Last edited: Aug 30, 2011
  7. loosecannon

    loosecannon break on through

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    there is no reason to check for bias in AM mode, only SSB.

    the fact that you are getting no reading in SSB mode hints to me that you are doing something wrong.
    if you are not getting a reading using the mA scale, its probably because that fuse is blown in your meter.
    usually there is one fuse for the mA scale and a larger fuse for the 10a scale.
    check the fuses in your meter.

    you can use the 10a scale to do the SSB bias testing, and although it will not be as accurate it will work.
    look for .05a for the driver and .1a for the finals.

    the voltage to the TP9 on AM sounds normal so something else is going on.

    try tuning the TX coils shown in the diagram Robb posted.

    sorry to say there's not much more advice i can offer without having the radio in front of me.

    might just be time to have a tech look at it.
    LC
     
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  8. Mr. Fortyfive

    Mr. Fortyfive Member

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    Yeah, I'm probably doing something wrong or something else is not working
    right in the radio, so I'm probably take it to a tech and let them check it
    out. But, appreciate your time and advice LC, You have a Good One and
    73's

    Mr. Fortyfive
     
    #8

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