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RCI 2995DX no transmit power

Discussion in 'Ham Equipment' started by Crambone, Sep 12, 2019.

  1. Crambone

    Crambone Active Member

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    So I will admit my mistake and tell you I accidentally shorted TP7 to the RX Section Shielding Box. After that I lost all TX Power on all Modes. I key the mike and no movement on Bird meter with 5-watt slug. When I un-key the meter on the radio bounces but bird does nothing. No Power No Modulation



    Need some help.
     

  2. ExitThirteen

    ExitThirteen Grumpy and Cranky

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    Sounds like you took out the AM pass regulator transistor. In this particular radio, the pass regulator transistor controls the voltage and current in ALL modes. You'll have to replace Q66, which depending on the year your 2995 was built, will be either a 2SB754, or a 2SB827. It's located on the right side of the chassis bolted up on the side next to the audio IC. There may be an outside chance that you'll have to replace Q67 as well, which should be a 2SB798. Replacing those should remedy your problem.

    Try replacing Q66 first, and see if it restores output before replacing Q67.

    Let us know how you get on.


    ~Cheers~
     
    Shadetree Mechanic likes this.
  3. Crambone

    Crambone Active Member

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    THANK YOU!
     
  4. Crambone

    Crambone Active Member

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    I pulled Q66 and borrowed a tester and got:
    BJT-PNP
    hFe = 261
    Ube = 542mV
    IC = 6.4ma
     
  5. ExitThirteen

    ExitThirteen Grumpy and Cranky

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    That HFE doesn't seem right at all... I can check a 2SB754 and see what the HFE is on it, but I still suspect a damaged pass regulator. Do you have a spare B754 or B827? Also, what was the number on the one you pulled?



    ~Cheers~
     
  6. Crambone

    Crambone Active Member

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    I pulled a B754 I don’t have any laying around so I just ordered a few.
     
  7. ExitThirteen

    ExitThirteen Grumpy and Cranky

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    I checked a couple of known good 2SB754's and I got an HFE of 101/104. I think there's something goofy with yours, I think it may have gotten damaged somehow.

    Let us know how you get on once you get your B754's in. (y)


    ~Cheers~
     
  8. Crambone

    Crambone Active Member

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    Thank you I will let ya know I just looked up on the data sheet and found this, Forward Current Transfer Ratio (hFE), MIN: 70
     
    #8 Crambone, Sep 13, 2019
    Last edited: Sep 13, 2019
  9. Crambone

    Crambone Active Member

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    Well I replaced the 2SB754 and still same so I’m waiting for the 2SB798 to arrive. Sent in 2 different packages ???. Strange but at least it’s on its way. Fingers crossed it’s going to be my first surface mount. Have the paste and hot air gun so should make it easier. This hobby is getting expensive, scope, spec analy, meters, solder station ........
    But I love every minute and without all your guys help I’d be in trouble!
     
    Shadetree Mechanic likes this.
  10. Handy Andy

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

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    And while you're at it, even see if you get power to the part.

    When you "short to the RX side" - I'm presuming you shorted it to the shield of the can by TP7 - means that don't just check for a blown Pass regulator, but the TRACE that goes to it, or From it - may have blown faster than the part.

    If you even get an Hfe out of the part (your SB754) means the part may be ok, just the TRACES may have opened up.

    So the parts may check ok, but the traces that feed the Driver and Final will need to be checked for continuity.
     
    Shadetree Mechanic likes this.
  11. Crambone

    Crambone Active Member

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    Ok good info I will try to check Wednesday as tomorrow is my boys day out drinking!
     
  12. Crambone

    Crambone Active Member

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    Ok I checked some points and this is what I have:

    TP7 6.169 Vdc stby .540Vdc xmit

    Q67 2SB798 Base 12.88Vdc stby and 1.43Vdc xmit
    Collector 6.161 stby and .540Vdc xmit
    Emitter 13.190Vdc stby and 13.08 xmit

    Q66 2SB754 Base 13.74 both stby and xmit
    Collector 6.170 stby and .540 xmit
    Emitter 13.193 both stby and xmit
     
  13. Crambone

    Crambone Active Member

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    UPDATE IM BACK AT IT!
    OK guys I know its been a while but been on some R&R so now I'm back at this issue.
    Update as of today,
    RCI-2995DX CF (EPT695015BR)

    Keys but no power

    Readings taken in Vdc RX unless stated

    Found Q60 (2SC2312C) bad replaced but no voltage to Base (.032Vdc RX / .035VdcTX)

    Q60 was reading as a resistor on my tester.

    Have 2.3Vdc at TP8

    Have 2.3Vdc at L29

    Have 2.3Vdc to C227 but only .034Vdc out the other end

    Can I assume C227 is bad? I jumped it and made NO difference still no power or modulation

    what else should I look for?

    Q66 was replace a while back and I'm reading:

    Outer pin connected to power supply orange trace 13.740Vdc RX & TX

    center Pin 2.33Vdc RX and .233Vdc TX

    Other outer Pin 13.245Vdc RX and 13.099 TX
     

    Attached Files:

  14. Doc813

    Doc813 Member

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    You do not want to jump c227 that's a very good way to blow the 2312 an other things in the circuit....
     
  15. Crambone

    Crambone Active Member

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    I should have written that i lifted it off and put a regular one in place temporally. Still no power out?
     

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