Zero 100 hum

the jewel in the crown
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Dadrepus
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Zero 100 hum

Post by Dadrepus » 20 Feb 2019 22:36

So, been working on my zero100 trying to get thing back to a functional state. Everything works, but not consistently. Auto start will move the tonearm, after several tries. Auto return same problem. But the big issue, hum from the speakers. Have checked for loose wires and resoldered those that were broken. 1 in the headshell. 2 underneath where audio plugs are. checked the tightness in the green wire attached to the motor and elsewhere. Just can't get the hum to go away. Any suggestions?

A70BBen
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Re: Zero 100 hum

Post by A70BBen » 21 Feb 2019 02:05

Have you verified that the tonearm wires are not broken where they flex as the tonearm head pivots? Could be hidden, broken inside the insulation.

Dadrepus
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Re: Zero 100 hum

Post by Dadrepus » 21 Feb 2019 02:23

if they were broken there would I still get stereo music? If I can still get music how do I check for hidden damage?

Pure_brew
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Re: Zero 100 hum

Post by Pure_brew » 17 Mar 2019 13:49

You can still get stereo sound with bad contacts. This can be replicated with a loose RCA cable, from turntable to phono preamp.

Can you describe the activity of the turntable during this noise? For example, if you brush the needle when the turntable is not in play, can you hear it, and is the hum active then? Like just selecting that phono input- you get hum? If so, this suggests a bad contact, or even a cartridge issue.

If the hum is only active when you place the needle on the record, it could be a cartridge issue, but more likely it is a transference of mechanical vibration from the motor though a hardened rubber idler, along with a need for bearing cleaning and lubrication.

I'm guessing that if it's not a contact issue, then it's the drive mechanism, especially since the turntable is working inconsistently.

Dadrepus
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Re: Zero 100 hum

Post by Dadrepus » 17 Mar 2019 14:51

I'm thinking it is a grounding issue. If I grab ahold of the motor while it is on, the hum goes away. I am essentially grounding it. I haven't had time to fully investigate the issue but will check further.

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Re: Zero 100 hum

Post by DSJR » 17 Mar 2019 20:38

These motors should have a green wire clipped via a tag to the motor top plate and going to a screw nearby on the chassis.

Grabbing the motor (how hard?) could be moving it in its mounts, which may have fatigued as two of the three grommets are softer than in previous models I think and they can sag.

Have a good look around the audio cable terminals. Garrards like this used to connect the chassis to the blue and green signal returns, which therefore 'earthed' the deck via the audio exit cables. I think there are wire links connecting the chassis to the RCA sockets as there used to be in Dual and Thorens decks of this period.

Dadrepus
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Re: Zero 100 hum

Post by Dadrepus » 17 Mar 2019 23:22

When I mean grab I just mean touch. I applied no force to the motor. I will look at the blue and green wires as well.

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