The Talking Machine Forum — For All Antique Phonographs & Recordings

It is currently Sat Sep 23, 2017 10:42 am

All times are UTC - 5 hours [ DST ]




Post new topic Reply to topic  [ 34 posts ]  Go to page Previous  1, 2, 3, 4
Author Message
 Post subject: Re: Gilbert portable.
PostPosted: Tue Sep 05, 2017 3:00 am 
Offline
Victor III
User avatar
F. Depero, "Grammofono", 1923.
Joined: Thu Feb 24, 2011 4:19 am
Posts: 521
Location: Italy
I have redone the soundbox, after having received a different gasket tubing gently provided by Carlos. This material is much softer and thinner than the usual white tubing for Exhibitions, and closing the soundbox was much easier.

To evaluate the results without too much placebo effect I tried to use the smartphone as an audiometer. The increase in volume turned out to be quite negligible, however I think that the overall sound was better: less "tight" and with a bit more bass. I also think there was less wear on the grooves, and on the needle's point as well.

As the diaphragm seemed still pretty much compressed, I redone once more by trying to cut one of the tubing in half (originally, the soundbox had a sort of half-tube below the diaphragm). However, the half-tube has proven impossible to install inside the soundbox, as it tended to curl and wouldn't stay flat, how hard I tried.

I then tried to made a back gasket with a ring of high quality paper. With the paper ring, the diaphragm sits very low into the soundbox, however the soundbox itself is shaped accordigly and the diaphragm will not hit the back. With this paper gasket it looked as if there would be a lot of compression inside the soundbox chamber, and I thought that perhaps this compression was what the arm needed to sound at its best. Again, this solution was closer to how the soundbox was originally found. However, playing an actual record shown that there was no significant sound improvement, while it was evident that the needlebar could no longer stay in the vertical "neutral" position, and it was also clear that the needlbar could move very freely when pulling the diaphragm, but was basically stuck when pushing the diaphragm. (As a side note, this confirms that this type of diaphragm is very stiff, it should be considerd and treated like a mica diaphragm).

As the latter condition seemed unacceptable, also in order to prevent groove damage, I've redone the soundobox once again, re-putting in place the pair of soft tube gaskets provided by Carlos. Unfortunately at this point, having redone the work many times, the needlebar tiny screw was stripped and is held in place more by wax than anything else, and one of the two spring-loaded screws of the needlebar hinges shown sufferings too. Quite obviously I will stop here and be happy with the results. This is probably the sound that this gramophone can deliver and used to deliver; I was perhaps too much impressed by the arm design and expected something different.


Top
 Profile  
 
 Post subject: Re: Gilbert portable.
PostPosted: Wed Sep 06, 2017 4:41 am 
Offline
Victor III
User avatar
F. Depero, "Grammofono", 1923.
Joined: Thu Feb 24, 2011 4:19 am
Posts: 521
Location: Italy
If the arm design was impressive, the arm's joins really aren't. The hinge at the elbow has no ball bearing or low-friction pivot: it is simply suspended at the top by a screw and held in place by the collar; the smooth movement and airtight of the arm relies only on overabundant lubrication. Quite obviously there is a *huge* backlash that it's impossible to deal with. On one hand maintenance is very easy as there is basically nothing that can be done :roll: but on the other hand this is possibly the crudest elbow hinge that I've seen so far. Are Gilbert's arms all hinged this way, even on more expensive floor units?

Finally good news under the table top: the motor is a Garrard 12A that looks very sturdy and in excellent shape. The whirring sound while cranking up is due to the anti-unwinding spring that surrounds the crank shaft. Sometimes it acts smoothly with no noise, sometimes it slides vibrating by tiny rapid "clicks" that result in the whirring sound. This spring has an old blob of grease on top. I think I've read that these springs are not to be lubricated or they may slip around the shaft. What do you usually do with them? Lubricate or keep dry?


Attachments:
IMG_3549.JPG
IMG_3549.JPG [ 315.56 KiB | Viewed 49 times ]
IMG_3550.JPG
IMG_3550.JPG [ 485.16 KiB | Viewed 49 times ]
Top
 Profile  
 
 Post subject: Re: Gilbert portable.
PostPosted: Wed Sep 06, 2017 6:10 am 
Offline
Victor III
Joined: Sun Mar 15, 2009 6:18 am
Posts: 592
The Garrard 12A is a good quality motor, and parts for it are relatively easy to find in case something breaks or wears out. When I touch these motors I normally clean the old grease out of the anti-backlash spring and add new grease. It was originally greased, as the evidence shows, so I don't see anything wrong with regreasing it. I never experienced such springs falling off or breaking - what I saw in some motors is wearout of the cam tooth that prevents the main gear to turn in reverse, causing slips when I crank it. but this happened only with very old motors. Yours look in good shape.


Top
 Profile  
 
 Post subject: Re: Gilbert portable.
PostPosted: Wed Sep 06, 2017 7:07 am 
Offline
Victor III
User avatar
F. Depero, "Grammofono", 1923.
Joined: Thu Feb 24, 2011 4:19 am
Posts: 521
Location: Italy
Thanks, will follow the advice!


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 34 posts ]  Go to page Previous  1, 2, 3, 4

All times are UTC - 5 hours [ DST ]


Who is online

Users browsing this forum: No registered users and 2 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
Powered by phpBB © 2000, 2002, 2005, 2007 phpBB Group
Americanized by Maël Soucaze.