newbie having an … angular proble

Posted: 3/13/2021 6:29:04 PM
Halla pacha

Joined: 3/13/2021

Hi, i’m Pacha, a 21yo swiss engineering student (EPFL for the connoisseurs)

I just picked up the theremin yesterday after a few weeks of listening over and over to Grégoire Blanc perfomances. It’s a lot of fun, and I was hoping to be able to play my newly acquired instrument tonight but after a min or so after having left the room to go to the bathroom i hear a big disheartening sound: my theremin was out of balance on its tripod and gradually made one of the tripod’s feet slide to the point of making the whole thing fall to the ground.

The bad news is that it fell on the pitch antenna, the antenna itself seems fine but the "antenna holder" has made a rotation of something like 15°. it doesn’t look so bad on the picture but with the antenna with that angle it’s rather unplayable as is…

I tried to put it back with bare hands but couldn’t acheive much, would anyone have any idea that i could (safely) attempt ?

Have a wonderful day

Posted: 3/13/2021 6:56:42 PM

From: Northern NJ, USA

Joined: 2/17/2012

I'd say just get a wrench and twist it back into position.

Posted: 3/13/2021 7:18:40 PM

From: Minnesota USA

Joined: 11/27/2015

Hi Pacha

That part is a standard right-angled plumbing fitting that is threaded into the wood. I believe the fitting is also glued in place during the factory assembly.  There is also a hole drilled inside the fitting (from inside the case) for a screw and solder lug for the wire attachment.

You have probably broken the glue loose and possibly torn the hole a little where the solder lug is located.  As Dewster suggests you can grip the fitting with a non-marring adjustable wrench and straighten it.  If you want to check for any wood tearing inside or to make sure that the wire is still firmly connected you can remove the cover by removing the screws located in the bottom edges of the case.  When you get in there make sure that the solder lug screw is tight (threads will be torn so be gentle checking this).  If you want to re-glue the fitting you can apply a little clear epoxy around where the wood and metal touch, but a better way to glue it is to use a thin CA glue (super glue) and place a drop or two around the edge of the wood hole.  Water-thin CA will wick into the threads and it should not break loose again.

If you do decide to re-glue it make sure that that antenna is as straight as you want it to be before gluing.  Also when handling water-thin CA glue be careful because it will run everywhere including up your sleeve.  Use just a drop or two.

If the wood is really torn out by the screw and it no longer holds, post a picture and we can go from there.  Hopefully you'll just need a wrench realignment.

Posted: 3/13/2021 9:12:39 PM
Halla pacha

Joined: 3/13/2021

First of all thank you both for the quick response, I couldn’t have dreamt… faster, and thank you Pitts8rh for the in depth explanation. Since i’m alone at home for the week and I have very little confidence in my DIY skills (rightfully so…), I went with Dewster initial advice,

The wood made some cracky sounds, but the angle is now barely noticeably small and it seems decently sturdy (wouldn’t move with my bare hands again), plugged back in and both antennæ seem to be working as intended.

Thank you again for the help, i’ll go back to training Edwig’s theme (my sister recognized it without entering the room, needless to say I was pretty proud !)

I wish a good afternoon to both of you.

Posted: 3/13/2021 9:27:01 PM

From: Minnesota USA

Joined: 11/27/2015

Here's what you would find inside if you open the case:

Posted: 3/14/2021 8:13:43 AM
Halla pacha

Joined: 3/13/2021

thank you for the picture Pitts8rh, my theremin wouldn’t make any sound this morning (I only checked very rapidly yesterday, I actually got busy the rest of the nigth) so I mustered the courage to open it. Nothing seemed out of the ordinary inside, so I didn’t really know what to lookout for. Here are a few shots i took. If i had to take a wild guess i’d say that the 4 coloured wires that go to the "north" of the pcb seem to be streched a bit (pic.3)

Do you guys have any idea ? 

Posted: 3/14/2021 7:09:28 PM

From: Minnesota USA

Joined: 11/27/2015

The stretch on the four wires looks pretty normal as long as none of them are broken where they are soldered to the board.

I just noticed that the red wire looks a little odd, maybe misaligned where it is soldered to the board in the bottom picture.  I think that this is the "Amp In" pin on that 10-pin connector. Does it look okay to you?

In that lower picture you can see the screw attaching the solder lug to the pitch antenna pipe fitting.  Give that solder lug a gentle wiggle to see if it is loose.  If that is a machine screw threaded into a tapped hole in the fitting you should not have a problem, but if it is a wood screw threaded through a hole in the fitting and into the wood then the screw hole is probably torn a little from the antenna rotation and could have loosened.  If the lug is tight then your problem is probably elsewhere.  BTW, that heavy wire going to the antenna over the patch of aluminum foil is actually for tuning, so try not to bend it if you don't have to.

What may have happened between when the theremin was working yesterday and today?  Check the following:
1)  Is there any sound at all, like a quiet background noise or hiss that goes away when the theremin is turned off? 
2)  Do you get any sound out of the headphone jack?
3) I'm not going to ask if you are getting power and the LED is on .
4) Try adjusting the volume knob over its range to make sure that audio isn't simply muted from the wrong setting.
5) Basically check everything in your power and audio connections to make sure all is correct before we go further into the theremin.
6) Give all the internal wires a good visual inspection but try not to poke around too much inside. 

If nothing obvious shows up come back and maybe we can have other suggestions.

Note to theremin nerds looking at the photos:  I had been wondering what Moog was using for the antenna inductors these days.  It looks like they have a new source or they are having them custom made.  These have natural color insulation with different slightly different cores.   

Posted: 3/15/2021 1:13:19 PM
Halla pacha

Joined: 3/13/2021

(uh I just deleted my last message instead of editing it, there is no way to restore it is there ?)

So today i tried some random things, and amongst those I found that plugging the jack in the "phone" hole instead of the "audio" actually makes sound come out (alleluia!). But the theremin is acting very strangely, the sound antenna goes from 0 →100 in a very short interval (less than 2 cm, it is incontrollable) and the sound that comes out is sounds to me much more nasal than what it used to.

Also : the volume of the sound goes to 0 when I get close to the pitch antenna, one hypothesis could be that the frequency of the sound is too high to be heard ? (maybe another tuning issue ?) →  edit : actually it might be 0 beat :

I suppose that the volume antenna problem can be fixed by toying with the tuning (haven’t looked into it yet) but for the case of the sound being different I wouldn’t be able to tell what to do about it.

Any thoughts ?

Posted: 3/15/2021 3:30:15 PM

From: Minnesota USA

Joined: 11/27/2015

Was this a factory-new theremin, and/or has it ever worked correctly?

You seem to have several different issues all at the same time and it's getting difficult to sort them out. If you do have major problems a return or repair at a Moog authorized service facility might be in order. You may have problems caused by the fall, but they also may be due to being new to the theremin and sometimes it takes a while to understand how everything works. Let's go through the basics.  You may already know these if you have been playing for a while, but to identify any real problem with the theremin these things have to be understood or set correctly first:

Important: Make sure your theremin is at least a few feet away from anything metallic.  Even plastic will affect the tuning so you want to have a reasonable open space on all sides of your theremin.

Sound, tone, timbre

1)  I wouldn't worry about this until you have the theremin pitch and volume set up correctly first. 
2)  Harshness is subjective, and your Etherwave's range of sounds might be perfectly normal but you haven't learned how to map out the most pleasing sounds using the infinite combination of the brightness and waveform knobs. 
3)  And even if the range of tones is normal you may simply not like how a stock Etherwave sounds (some don't) in which case there are modifications that can be made.  But not yet.

Volume Side

1) Make sure that you've watched online videos showing how to tune your theremin.  Carolina Eyck has some good ones.
2)  The volume knob (not the phones volume knob) sets the response contour of the volume antenna.  Fully CCW will give the most gradual response with the range from full cutoff to full volume occurring over 10cm or more of movement with your volume hand. 
3)  Fully CW will result in a very sharp response like the one you describe going from cutoff to full volume in 2cm or even less, and this generally occurs very close to the loop antenna. 
4)  Severe mistuning of the volume circuit (I'm talking about internal tuning) can indeed result in total cutoff or muting of sound - that's why I previously suggested that you check the full knob range if you're not hearing any sound.  If internal tuning is correct then any tuning of the volume knob will allow you to hear something somewhere, even if the knob needs to be off center for your idea of what is normal.
5)  The response of the volume side will be gentler if you play flat-handed above the antenna rather than off the front edge of the loop.  Flat-handed playing has some limitations though as you'll find later.
6) Don't worry if you hear a chirp if you touch the volume antenna.  Etherwaves do that.

Pitch side

1)  See 1) above. 
2)  You've no doubt noticed that tuning the pitch knob (or volume) is a hit or miss process since your arm affects the pitch.  For the Etherwave you should be seated or standing slightly to the volume-side of center in front of the theremin so that your wrist, lower thumb knuckle, or some other preferred reference just reaches the pitch antenna.
3)  Tune the pitch knob until the sound stops at zero beat.  Now turn the knob CCW past the zero-beat until the sound starts again and you hear a low note. As you bring your closed hand vertically back against your chest the note should lower until ideally it is zero at your chest, and you should adjust the knob until this happens. This way you are always increasing pitch as your arm moves forward.
4) Watch Carolina Eyck to learn how to further refine the pitch knobs setting so that you can obtain octave intervals when going from a closed hand to open hand position.
5) Be forewarned that sometimes a mistuned Etherwave won't start making sound until you get very close to or touch the pitch antenna.  It will usually continue working after that but any power interruption or even plugging in a cable might kill the oscillator and required doing the same thing again.

Try to take the above steps, and assuming you do have some real problems related to the fall, try to sort them out as volume or pitch specific and describe what you find.

Posted: 3/15/2021 4:44:14 PM
Halla pacha

Joined: 3/13/2021

It is a factory new, it was working correctly before the fall (as can be heard on my first recording)

to see the difference with how it sounds now, I made a clip showcasing the strange volume range and sound.

it’s tuned approximately to get 0 beat at my chest (it was harder to tune because it wouldn’t make sound without my hand over volume antenna).

Few things i noticed :
- the theremin used to make sounds if there was nothing on the volume but something in range of the pitch antenna, not the case anymore
- the volume knob basically does nothing except cutting all sounds past a certain threshold (it doesn’t change the smoothness of the volume gradient)
- the lectern that seems rather close in the video (seems closer than it was) didn’t impact the playing when removed

bonus clip to more clearly see how the volume gradient is too big to do anything :

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