[Jukebox-list] ami continental sound problem

Wed Sep 12 01:36:02 PDT 2007

So you can actually hear the rumble at the begining of the record, at a high 
volume. It becomes louder towards the end of the lead out grove, which I 
assume is the AVC kicking in. If I pick up the tone arm just before the cut 
off switch and place it at the beginig of the record the rumble is the same 
volume, until the music starts.

I don't think it is the avc completely, because the rumble is always 
present, even at the begining of the record. It is only ever there when the 
volume is up.

All those parts you mentioned have been oiled, Ron. The idler wheel is 
touching the motor. The bottom of the idler wheel scrapes the motor (the 
black case) when you move it... if that makes sense. So the bottom of the 
idler wheel contacts the top of the motor. Is it supposed to be like this? 
Maybe thats where the vibration is coming from.

>From: Ron Rich <ronnnrich at yahoo.com>
>Reply-To: Jukebox mailing list <jukebox-list at lists.netlojix.com>
>To: Jukebox mailing list <jukebox-list at lists.netlojix.com>
>Subject: Re: [Jukebox-list] ami continental sound problem
>Date: Tue, 11 Sep 2007 08:04:45 -0700 (PDT)
>
>Hard to guess, but it could be the rubber mounts, and / or the spring that 
>holds the idler wheel against the turntable. If someone has installed a 
>"stiff" spring that will happen.  Also, the mechanism itself should be 
>"floating" on it's suspension. Have you oiled the TT shaft itself , idler 
>wheel,  and the tone arm pivots?  Ron Rich
>
>Daniel Gray <dj_daniel88 at hotmail.com> wrote:   Thanks for your responses.
>
>The noise disappears when I lift the tone arm off the record. The 
>hum/rumble
>starts almost immediately on the lead out groove, you can hear it fading in
>when the song fades out. The cut off switch is adjusted correctly.
>
>I still had the bolts holding the mech down in the cabinet. I didn't know
>they are supposed to come out. I took them out, but it hasn't made any
>difference the noise is still there.
>
>Do you think it could be the rubber mounts?
>
>
> >From: Ron Rich
> >Reply-To: Jukebox mailing list
> >To: Jukebox mailing list
> >Subject: Re: [Jukebox-list] ami continental sound problem
> >Date: Sun, 9 Sep 2007 10:03:14 -0700 (PDT)
> >
> >Jay is correct, but I might add that the "trip-off switch" adjustment may
> >be off, allowing the AVC more build up-time, prior to record trip-off. If
> >the hum is electrical ( present with the needle off the record), check 
>out
> >the tone arm/cartridge grounding circuit. Ron Rich
> >
> >Jay Hennigan wrote: Daniel Gray wrote:
> > > Hello again!
> > >
> > > So I have sorted the crossover problem. I have another problem I need 
>to
> > > sort out. When the jukebox is at a high volume during lead out section
> > > of the record, the jukebox hums really loud. Sometimes it sounds like
> > > its going to take off! The woofer shakes really violently, I turn it
> > > down because it can't be good for it. It doesn't happen on the lead in
> > > section of the record. Do you know what could be causing this?
> >
> >Hello, Daniel and welcome to the list! I had somewhat of the same thing
> >with my Wurlitzer 1900. The underlying cause is probably mechanical
> >rumble coupled to the stylus. It could also be magnetic hum pickup from
> >the motor to the cartridge, or even acoustic feedback from the woofer.
> >Try carefully lifting the arm just off of the surface of the record
> >right at the end of the record and hold it there for a few seconds to
> >see if the hum appears. If so it is electrical or magnetic from the
> >motor. If not, it's mechanical.
> >
> >There's a reason for waiting a few seconds, and it is why you don't hear
> >the hum at the beginning of the record or while it's playing. The
> >amplifier has AVC, automatic volume control. To compensate for records
> >of different loudness and have the jukebox volume relatively constant, a
> >circuit in the amplifier boosts the volume for quiet records and lowers
> >it for loud records. There is a time constant of about one to four
> >seconds for this to adjust so it doesn't obviously "breathe".
> >
> >The muting circuitry forces the AVC to be at its lowest volume during
> >record transfer and immediately after it unmutes. This plus the time
> >constant brings up the volume up slowly at the beginning of the record,
> >hiding any crackle in the lead-in groove.
> >
> >At the end of the record, however, the lead-out groove will have a few
> >seconds of silence. The AVC treats this silence as very low volume
> >music and turns up the amplifier to compensate. Thus, any problems with
> >rumble or noise that exist are amplified.
> >
> >You'll want to find and fix the source of the noise, of course, but it
> >may also be worthwhile to make the AVC a little less aggressive. The
> >aggressiveness is adjustable on Seeburg amplifiers, but I don't think it
> >is on the AMI. This might require some component changes in the
> >amplifier. Depending on your expertise you might want to look into
> >this. Fix the cause of the underlying noise, as well.
> >
> >--
> >Jay Hennigan - CCIE #7880 - Network Engineering - jay at impulse.net
> >Impulse Internet Service - http://www.impulse.net/
> >Your local telephone and internet company - 805 884-6323 - WB6RDV
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