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FM hiss, vintage 1973 receiver

Discussion in 'Electronic Repair' started by mc, Jan 3, 2006.

  1. mc

    mc Guest

    FM stereo receiver, vintage 1973, has a noticeable background hoise
    (hiss/white noise) on FM stereo regardless of the incoming signal level. It
    disappears completely upon switching to mono.

    Is this normal in a receiver of that age? If not, what components are
    likely to be deteriorating?
     
  2. Nothing wrong with it, other than it should have been thrown out 20
    years ago. Why are you still dicking with old recievers. Don't you have
    a girlfriend or a life?
     
  3. JANA

    JANA Guest

    It is impossible to guess at what can be wrong. There are many components
    involved to receive, and process the signal. An experienced tech who is
    knowledgeable in servicing tuners should be able to troubleshoot the tuner
    for you, and find the failed components.

    --

    JANA
    _____


    FM stereo receiver, vintage 1973, has a noticeable background hoise
    (hiss/white noise) on FM stereo regardless of the incoming signal level. It
    disappears completely upon switching to mono.

    Is this normal in a receiver of that age? If not, what components are
    likely to be deteriorating?
     
  4. If the receiver has a multipath filter, try that.
     
  5. Guest

    Guest Guest

    Aaaah, shaddap before we bomb Dresden. Again.


    Hugs & kisses,
    Francois.
     
  6. mc

    mc Guest

    I knew that already, except the "impossible" part.
     
  7. gb

    gb Guest

    How good is your antenna for the station that you are trying to receive?
    Do you have an outside antenna?

    These symptoms are common for fringe reception (stereo not full quieting -
    but mono is better).

    If you are trying to receive the signal with a small dipole in a tall steel
    and concrete high rise - then you are not getting sufficient signal strength
    to the receiver.

    gb
     
  8. That would be useful. ;-) Do you mean multiplex?
     
  9. Peter Larsen

    Peter Larsen Guest

    mc posted a question compliant with usenet standard: 3416554677697809809
    section B, page 27, paragraph 8: Any initial question must omit at least
    one piece of vital information, otherwise it can not be considered for
    followups.
    Noise in Stereo FM is out of phase between the channels, and thus
    disappears when the signalchannels are added to mono.
    This is not about age - rather about quality, unless of course something
    is broken and age, if it was left unused for an extended period of time,
    may have caused some components to deteriorate. Have you just found or
    gotten it or do you know for sure that it has deteriorated. Try adding
    the elementary information: make and model, someone may then know
    whether it was likely to have been good or bad ex works.


    Kind regards

    Peter Larsen
     
  10. Smitty Two

    Smitty Two Guest


    Is it only on FM, or with other sources, too? If it's noisy from a line
    input too, a dirty stereo/mono switch could be at fault. Some of those
    old pushbutton types were pretty marginal.
     
  11. mc

    mc Guest

    How good is your antenna for the station that you are trying to receive?
    A 1/4 wave ground plane in the attic of a wood-framed house. Some of the
    local stations (within 5 miles) are very strong, and I can get some stations
    80 miles away (not with good audio). The antenna is not the problem. What
    concerns me is that even the very strongest signals do not give full
    quieting on stereo.
     
  12. mc

    mc Guest

    FM stereo receiver, vintage 1973, has a noticeable background hoise
    That I knew...
    Nikko STA-5010. FM stereo demodulator is a UPC554C chip.

    Circuit diagrams somewhere on www.covingtoninnovations.com/audio.

    Thanks!
     
  13. mc

    mc Guest

    Only on FM stereo. No problems with any other signal source, stereo or
    mono. Anyhow, would a dirty switch produce continuous hiss?
     
  14. Asimov

    Asimov Guest

    "mc" bravely wrote to "All" (03 Jan 06 00:00:37)
    --- on the heady topic of "FM hiss, vintage 1973 receiver"

    mc> From: "mc" <>
    mc> Xref: core-easynews rec.audio.tech:186013
    mc> sci.electronics.repair:353686

    mc> FM stereo receiver, vintage 1973, has a noticeable background hoise
    mc> (hiss/white noise) on FM stereo regardless of the incoming signal
    mc> level. It disappears completely upon switching to mono.

    mc> Is this normal in a receiver of that age? If not, what components are
    mc> likely to be deteriorating?


    Vintage 70's equipment is making a comeback and is all the rage now.
    A big noise is absolutely normal between stations if there is no
    muting circuit but when tuned to a station the noise should drop
    dramatically. It is also normal to have a little extra hiss in stereo.
    However I have no idea how much hiss is normal for your particular
    receiver. If it seems excessive then perhaps the components to look at
    are electrolytic capacitors around the stereo decoder/demultiplexer
    circuitry. If you can find a separation adjustment trimmer, sometimes
    reducing the separation a little can lessen the hiss significantly
    without affecting the stereo effect too much.

    A*s*i*m*o*v

    .... A stereo system is the altar to the god of music.
     
  15. Asimov

    Asimov Guest

    "null" bravely wrote to "All" (03 Jan 06 05:56:45)
    --- on the heady topic of "Re: FM hiss, vintage 1973 receiver"

    nu> From: ((null))
    nu> Xref: core-easynews rec.audio.tech:186020
    nu> sci.electronics.repair:353710


    nu> In article <>,
    nu> Erich J. Schultheis, The Man with the 15 inch Cock.


    nu> Aaaah, shaddap before we bomb Dresden. Again.

    Don't feed the trolls!

    A*s*i*m*o*v

    .... Your E-Mail has been returned due to insufficient voltage.
     
  16. David Tweed

    David Tweed Guest

    Don't be so sure. It used to be (and probably still is) that commercial
    FM transmitters were almost always horizontally polarized. A pair of
    crossed folded dipoles (made from 300 ohm twinlead) in your attic will
    probably have markedly superior performance to your vertical quarter-wave.

    -- Dave Tweed
     
  17. mc

    mc Guest

    Asimov wrote:
    Vintage 70's equipment is making a comeback and is all the rage now.
    A big noise is absolutely normal between stations if there is no
    muting circuit but when tuned to a station the noise should drop
    dramatically. It is also normal to have a little extra hiss in stereo.
    However I have no idea how much hiss is normal for your particular
    receiver. If it seems excessive then perhaps the components to look at
    are electrolytic capacitors around the stereo decoder/demultiplexer
    circuitry. If you can find a separation adjustment trimmer, sometimes
    reducing the separation a little can lessen the hiss significantly
    without affecting the stereo effect too much.


    Thanks. Several people are saying that. I'll also look at the power supply
    for the tuner section (which has its own regulator). The power may be noisy
    or not the correct voltage.
     
  18. mc

    mc Guest

    Thanks, I'll try that.

    I thought they were going to vertical polarization because of car radios.
    I'm wondering where I read that, and whether it's true.
     
  19. David Tweed

    David Tweed Guest

    I'm pretty sure that commercial VHF services like FM radio and TV
    prefer horizontal polarization because of fewer problems with
    absorption and/or diffraction from vertical objects such as trees
    and poles.

    Also, most customers for these services have fixed antennas, and
    can do horizontal just as easily as vertical. FM radio in the car
    is an exception, as you note, but most cars these days either have
    a horizontal dipole in the window glass somewhere, or a whip that
    has a significant amount of tilt.

    On the other hand, VHF services that are intended *primarily*
    for mobile customers (public service bands, etc.) use vertical
    polarization because the car antennas really want to be vertical
    whips for mechanical simplicity.

    -- Dave Tweed
     
  20. Karl Uppiano

    Karl Uppiano Guest

    Almost all commercial FM stations in the US are circularly polarized (1/2
    power vertical; 1/2 power horizontal, 90 degrees out of phase). That covers
    both types of antennas, and if you have a CP receiving antenna, you can
    dramatically reduce multipath if it is oriented toward the transmitter.
     
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