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Sound Technology 1000A Stereo Generator problems

Discussion in 'Electronic Repair' started by Pete KE9OA, Oct 3, 2006.

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  1. Pete KE9OA

    Pete KE9OA Guest

    Hi,

    Has anybody ever run into a problem with this unit, whereby the 19kHz pilot
    level is intermittent? It doesn't seem to be a thermal problem, and I have
    cleaned the switches and controls. I don't know if the phase adjustment pot
    on the main board might have a problem.
    Looking at the 19kHz signal on an oscilloscope appears to show a steady
    state signal level; however, the modulation meter on the RF generator itself
    shows an erratic level, suggesting later stages in the signal chain.
    Can anybody help?

    Pete Gianakopoulos
     
  2. mark

    mark Guest

    If your interested In the 19khz signal and it looks ok at the output
    of the generator if thats what your saying then wouldn't you check the
    modulation producing circuits or the meter chkt itself.
     
  3. TimPerry

    TimPerry Guest

    it might be time to replace some caps and do the maintenance that is usually
    needed on old test equipment. check solder joints, broken wires, etc.

    look at the left minus right signal at the output with the 'scope. use a low
    audio frequency like about 100 Hz.
    if it looks like a string of beads (double sine wave) you are in pretty good
    shape.
    expand the 'scope to view the crossover point closely, the waveform should
    be symmetrical.

    if you are referring to a jitter that occurs when audio such as music is fed
    to left and right it could very well be a normal situation. the demodulated
    FM pilot usually shows some jumping around even on the some of the finest
    broadcast generators that are made.
     
  4. Pete KE9OA

    Pete KE9OA Guest

    Hi Tim,

    Thanks for the insight. The erratic indication on the meter shows up with
    the 19kHz only; this is with no other audio input, including the internal
    oscillator.

    Pete
     
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