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Dual Motor Hum - Impending Project

Dual Motor Hum - Impending Project

Postby DaveyW » Tue Feb 03, 2015 11:17 pm

Looks like I'm going to have to dig out the toolbox :evil:

I've been noticing a little background noise recently with the 1219.
Sort of a hum which is present when the stylus is set down on the record (so not grounding/earthing driven).

Tonight I did a bit more investigating and it seems to be due to motor vibration which I can feel by touching the body when it is running.
Interestingly I can run the motor without the idler wheel engaged.
Dropping the needle onto the lead in with stationary platter and there's the hum.
Engaging the idler and running the platter doesn't have a significant impact on the tone or amplitude.

This rules out motor pulley/idler issues.

It's got to be motor vibration exciting the plinth and platter through the main bearing.

There's only one thing for it - A motor strip down, bearing check, clean and lube.
I've got a copy of the 1219 DIY service guide that covers this - doesn't look too tricky - but knowing my luck .... :roll:

Getting late now - one for a future evening.
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Re: Dual Motor Hum - Impending Project

Postby satanfriendly » Wed Feb 04, 2015 1:10 am

If a strip down and service doesn't work, try a couple of 'O' rings around the motor casing. Worked wonders on my PT in the past.
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Re: Dual Motor Hum - Impending Project

Postby DaveyW » Wed Feb 04, 2015 9:07 pm

Found myself some free time tonight - Why not give this a bash?

So the motor was removed and stripped down

Image

Both bearings dry as a bone :evil:

But thankfully clean and no visible damage or wear
In fact, for a motor that is over 40 years old it was in amazing condition.

Cleaned, lubed, re-assembled and reinstalled

And ........ BINGO! :Banana

A MASSIVE improvement :cool:

Now only a tiny bit of hum stylus on record with the platter stationary, but at high volume.
Just blends into the background when spinning and not at all audible.

Glad I did this when I did :nodding
Those dry bearings would not have lasted too long given the use this deck gets.
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Re: Dual Motor Hum - Impending Project

Postby satanfriendly » Wed Feb 04, 2015 11:18 pm

Great to hear Davey :rock :rock :rock

Something I might get around to with the Seiki, greasing the bearing, but haven't a clue or any instructions how to get in there :scratch
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Re: Dual Motor Hum - Impending Project

Postby DaveyW » Wed Feb 04, 2015 11:52 pm

Thanks SF :thumb

Being of this vintage definitely helps

Once removed from the deck it looks like this

Image

Two through bolts (one already removed in this pic) and some gentle prizing

And it came apart

Image

The rotor assembly slid out and both bearings then became easy to access for the clean and lube.

Image

In the end the whole job from start to spinning took no more than two hours

Hopefully the Seiki will be just as straight forward Image
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Re: Dual Motor Hum - Impending Project

Postby bauzace50 » Thu Feb 05, 2015 2:41 am

Looking good!
Buena Suerte!
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Re: Dual Motor Hum - Impending Project

Postby DaveyW » Thu Feb 05, 2015 9:19 pm

bauzace50 wrote:Looking good!
Buena Suerte!

:thankx - And Sounding Even Better :cans
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Re: Dual Motor Hum - Impending Project

Postby beatcomber » Fri Feb 06, 2015 3:21 am

Here's another easy mod that Seth (No Transistors) on AudioKarma showed me when I picked up my 1219 after he fixed it...

You know that hollow ring around the perimeter of the platter on the underside? Fill it with latex or silicone caulk to dampen it.
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Re: Dual Motor Hum - Impending Project

Postby DaveyW » Fri Feb 06, 2015 1:12 pm

beatcomber wrote:Here's another easy mod that Seth (No Transistors) on AudioKarma showed me when I picked up my 1219 after he fixed it...

You know that hollow ring around the perimeter of the platter on the underside? Fill it with latex or silicone caulk to dampen it.

Thanks for the tip :thumb
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Re: Dual Motor Hum - Impending Project

Postby DaveyW » Sun Feb 08, 2015 3:09 pm

Platter peripheral cavities filled.
In fact went the whole hog and filled the full section.

Ended up going for Plasticine, I think this is similar to Plasticlay?

Image

About 1lb of material added.

The two dimples correspond to where there was some incremental material in the opposite side
Looks like these were two holes drilled for balancing.
The dimples were an attempt to retain balance.
When the deck is inclined and spun to standstill it seems not to be settling in a consistent position - looks like the balance is reasonable.

Difficult to say if there's much of a hum/rumble improvement as it was pretty quiet before.
Might be the fact I've only just swapped back to the Grado from the Denon, but bass feels a little tighter and possibly a tad fuller????
If this is the case then it's very subtle but welcome non-the-less.
One thing that definitely has changed is the spin down time which has increased by about a minute - obviously no surprise. But am expecting the increased inertia will help speed stability as well as reduce the impact of any motor ripple.

Listening now as I type and this deck keeps bringing a smile to my face.
For a 40+ year old, 33/45/78 fully auto stacker unit this ain't shabby at all :mrgreen:
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