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Conference napalm::commusic_v1

Title:* * Computer Music, MIDI, and Related Topics * *
Notice:Conference has been write-locked. Use new version.
Moderator:DYPSS1::SCHAFER
Created:Thu Feb 20 1986
Last Modified:Mon Aug 29 1994
Last Successful Update:Fri Jun 06 1997
Number of topics:2852
Total number of notes:33157

2319.0. "HELP:Carver PM-100 PROBLEM!" by FGVAXX::LAING (Soft-Core Cuddler*Jim Laing*282-1476) Fri Apr 13 1990 20:53

    [Also posted in AUDIO; if the moderator feels it shouldn't be in
    here, let me know ... thought many COMMUSIC people have plenty of
    experience with amps/power/trouble-shooting ...]
    
        I'm having problems with my Carver PM-100 amp (this is their
    1-rack-space "pro" amp).  What happens is this: When the amp is
    first powered up, one and only ONE channel has a noticable distortion
    or buzziness.  It's most notible in the high-frequency end.  The
    distortion/noise GOES AWAY within about 60 seconds.  
    
    I took the amp to have it serviced (still under warranty)...they
    found NO PROBLEM!  I went to pick it up, and tested it at the shop:
    yep, it worked FINE, no problem even immediately after power up.
    
    I take the amp home, set it up - THE PROBLEM's STILL THERE?!?!?!
    And it's definitely the LEFT channel, verified by switching the
    speakers and input jacks.  Also, I have another amp right there
    (the ADCOM GFA-1) and set up IDENTICALLY, it has NO problem, so
    I know that the problem isn't in my source or related to my speakers.
    
    Any idea what could cause a problem in ONE channel at my house,
    yet the problem doesn't appear when the amp is in the shop?  I'd
    thought maybe it's power (AC) related, but only one channel?  I'll
    be doing some more experiments .. anyone care to offer some ideas
    or answers?
    
    	thanks,	
    	Jim
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2319.1Check the contactsCADSE::KOMISKYThu Apr 19 1990 00:3111
    Check the fit of the left channel connectors with your cable
    connectors. Make sure the signal and ground contacts are tight and
    dirt free. Connectors actually change size as they warm up - so any gap
    may disappear after the equipment warms.
    
    Beware also of cracks in your cables that create intermittent breaks or
    low quality connections that may change as the cable heats up.
    
    Chronic victim of imperfect connectors
    Dennis
    
2319.2check connections firstSTROKR::DEHAHNWhat a difference a RAY makesThu Apr 19 1990 13:356
    
    If the Carver has relays on the outputs then one of them could be
    getting crappy.
    
    CdH
    
2319.3PoltergeistsTALLIS::PALMERColonel ModeMon Apr 23 1990 19:537
    Since it didn't do it at the shop but does at your home it leads me to
    believe that it has something to do with your home environment. If the
    cable connections are OK (verify by swapping L/R) try hooking up your
    amp far from any other equipment and check the grounding of the ac
    power. It might be an obscure RFI or ground loop problem.
    
    Chris
2319.4CADSE::KOMISKYTue Apr 24 1990 00:469
    An obscure RFI or ground loop problem that disappears after 60 seconds
    suggests a thermal component to the problem or an oscillation that
    requires 60 seconds to die down. 
    
    Or a timer circuit on the relay output is partially opening the relay
    and degrading the signal.
    
    Is the delay always 60 seconds? Even when the equipment is hot?
    
2319.5More ...FGVAXX::LAINGSoft-Core Cuddler*Jim Laing*282-1476Fri Apr 27 1990 19:5815
    No, the delay is only when it's turned on COLD.  As for the problem not
    showing up in the store ... well, that's what the tech said ... not
    believing him, *I* tried it in the store (amid screaming guitars/keys/
    drums/people/etc) and really thought that I, too, heard NO problem in
    either channel at the store.  
    
    Looks like I'll have to do some more experimenting at home ... then
    maybe taking it back into the shop (store) ...
    
    Other than a 60-second inconvenience, this isn't really a problem for
    me - once the amp "warms up" it works fine thru the whole gig.  But,
    I have to wonder if this is a harbinger of further problems down the
    line ...
    
    	-Jim
2319.6A good starting point...CADSE::KOMISKYFri May 04 1990 22:468
    Buy a can of the spray coolant for electronic troubleshooting 
    (try Radio Shack or U-DO-IT Electronics type places) and see
    if you can recreate the problem. Maybe it is only a thermal problem.
    
    If you cannot recreate it by chilling the components, the circuit
    board, or the connectors, then you have a real headache.