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SDR40 v6.1 TX/RX stopped working

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  • ian mcphedran
    Hi all, after lots of help from this group members I got my tx/rx v6.1 working on Rocky. I am using an maudio D44 amp for line in (1&2) and line out (3&4) and
    Message 1 of 47 , Jul 28, 2007
      Hi all, after lots of help from this group members I got my tx/rx v6.1 working on Rocky.
      I am using an maudio D44 amp for line in (1&2) and line out (3&4) and the built in soundmax audio system of my Dell PC for audio output.
      I worked one contact with a G station on CW and another contact with a DL station on BPSK so all was well until yesterday.
      Suddenly I am back to symmetrical output from the RX, lots of sensitivity but mirror image upper and lower band signals about the null point 7.056MHz. All plugs and sockets are correct but curiously the 'Ring' channel is not working into the D44. I broke the contact on tip and ring in turn and the tip channel is giving output but the ring circuit is not. Reversing the inputs gives no output, so the tip signal doesn't get through the former ring channel, and the ring signal doesn't give an output on the former tip channel.
      my settings on the D44 are:
      Delta 44 Hardware settings
      Internal xtal
      96,000
      Rate locked
      Single and in sync
      disable audio application use of monitor mixer and patch bay router
       
      o/p's     in1 to in4
      +4dbu      con
       
      --------------------------
      Rocky view /settings /audio
      I/Q input device   mAudio Delta44 1/2
      96 kHz
      left/right = Q/I
      audio output device   Soundmax digital audio
       
      Suggestions to return it to working, welcome!
       
      Ian GM3GTQ


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    • Len Warner
      ... Perhaps, but output near the +ve rail could be: a) inputs driven to output saturation b) output pulled high externally (i.e. by a pins 7-8 short) c) device
      Message 47 of 47 , Aug 3, 2007
        >U8 86 F
        >U8 pin 7 reads 4.2V
        >
        >Ian
        At 2:44 am ((PDT)) Thu Aug 2, 2007, in Digest 1865 Tony Parks wrote:

        >Sure looks like U8 is a problem.

        Perhaps, but output near the +ve rail could be:
        a) inputs driven to output saturation
        b) output pulled high externally (i.e. by a pins 7-8 short)
        c) device failure which also emulates (a) or (b).

        Both (b) and (c) can explain the U8 heating
        but only (c) is that device's fault.
        (There's no source for the heating current in case (a).)

        Meanwhile, none of these explain why:
        d) Q9 ran hot and
        e) Q9 replacement ran hot
        This doesn't seem to be in a related part of the circuit,
        so was Ian just unlucky with two rogue 2N3904?

        [BTW, my apologies for saying that Q9 collector pad voltage
        3.63V with Q9 removed seemed too low. I recalculated as
        3.64V - within the DVM last digit uncertainty.
        (Vcc-Q8vbe) * R40/(R35+R40) + Q8vbe =
        (4.32-0.65) * 22.1/(4.99+22.1) + 0.65 = 3.64V ]

        >Let me know what components you need to restore your board
        >and I will send them right away at no cost.

        I continue to admire your outstanding support for this project;
        "May Great Leader Tony live ten thousand years!"


        Regards, LenW
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