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Stereo indicator lamp, vintage receiver

Discussion in 'Electronic Repair' started by mc, Jan 2, 2006.

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  1. mc

    mc Guest

    Stereo receiver, vintage 1973, with uPC554C (ECG1142) FM demodulator chip.
    Sounds fine, but the stereo indicator lamp (newly replaced) is on nearly all
    the time, when any FM signal is tuned in (even a very weak one), but never
    at full brightness. That is not how I remember it behaving, years and years

    Specified bulb is 8 V 40 mA; actual bulb is 8 V 35 mA.

    There is no potentiometer to adjust anything to do with the stereo indicator

    Any thoughts? I plan to replace all the electrolytic capacitors in the
    system, a few of which are around the uPC554C. Perhaps one of them is
  2. I have a thought. Who needs FM anymore? I takes it it has RCA inputs,
    so if I were you, I would get a Sirius Satellite Receiver listen to
  3. CJT

    CJT Guest

    Why would he want to pay for something he can get for free?
  4. DaveM

    DaveM Guest

    FM is still a very viable medium for entertainment... just because one
    person might think it's the cat's meow doesn't mean that it's obsolete.
    The adjustment, if any, would be for the pilot level, pilot frequency, or
    something similar. I couldn't find a datasheet for either the uPC554 or the
    NTE1142, so it's hard to visualize the circuitry around the IC. If you have
    a copy of the schematic for your receiver, scan the FM portion and post it
    on alt.binaries.schematics.electronic
    Replacing the capacitors may help, especially if the unit has been on the
    shelf for many years. It may fix problems than you don't even realize that
    you have.

    Dave M
    MasonDG44 at comcast dot net (Just substitute the appropriate characters in
    the address)

    Never take a laxative and a sleeping pill at the same time!!
  5. James Sweet

    James Sweet Guest

    Is there a transistor to drive the lamp? It's possible it's become
    leaky. Your replacement lamp should work just fine so there's some fault
    in the receiver. It's remotely possible it was damaged when the original
    lamp failed.
  6. James Sweet

    James Sweet Guest

    Come on now, quit feeding the trolls, at this rate I'm gonna end up with
    half the people in this group killfiled.
  7. Because it's all 100 percent commercial free music.
  8. have fun talking to yourself then.
  9. Until they get a substantial listener base.
  10. mc

    mc Guest

    Thanks. I haven't actually gotten around to doing that, but it's in the
  11. mc

    mc Guest

    Is there a transistor to drive the lamp? It's possible it's become leaky.
    The driver transistor is inside the uPC554C.
  12. Franc Zabkar

    Franc Zabkar Guest

    Pin # Function
    1 19kHz tank
    2 19kHz tank
    3 Input
    4 Stereo switch
    5 Mute switch
    6 Lamp drive
    7 Ground
    8 NC
    9 Vcc
    10 38kHz tank
    11 Left channel out
    12 Right channel out
    13 38kHz tank
    14 Filter net

    - Franc Zabkar
  13. mc

    mc Guest

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