static electricity spark now etherwave is silent

Posted: 1/22/2014 1:36:15 PM
Thierry

From: Colmar, France

Joined: 12/31/2007

The theremin is designed to be played without touching the antennae, dewster! Thus it's not a design problem, but the user's fault if he doesn't touch a grounded part, i.e. the front panel, to discharge himself before touching the antennae, though. Such simple precautions are (IMHO) self-evident.

There are theremin models which have more sophisticated circuits and/or additional electronic protection. But the Etherwave is the cheapest theremin which qualifies as a music instrument (while the still cheaper ones are simply toys) and its circuit design is about 20 years old. You can't expect to get a new Mercedes when you pay only for a used Fiat...

Posted: 1/22/2014 2:39:24 PM
Gibarian

From: Germany

Joined: 12/27/2013

Couldn't you put an insulating sleeve on both the pitch and the volume antenna?

I noticed that Thomas Grillo has one on his Etherwave.

Thomas Grillo's antenna sleeve

Posted: 1/22/2014 4:37:30 PM
dewster

From: Northern NJ, USA

Joined: 2/17/2012

"The theremin is designed to be played without touching the antennae, dewster!"  - Thierry

Huh?  Players touch the volume loop all the time, often resting their hand on it to mute.

We, as electrical types, tend to follow practical ESD procedures.  But when designing a product for the general public, well, one should take into account that lots of shit one can't control tends to happen.

Posted: 1/22/2014 7:59:00 PM
Thierry

From: Colmar, France

Joined: 12/31/2007

Huh?  Players touch the volume loop all the time, often resting their hand on it to mute.

Not me, my volume field is adjusted to mute the sound already when my hand is 2cm above the loop. Out of that, there is my ashtray hanging in the loop for most of the time... ;-)

Posted: 1/22/2014 8:56:28 PM
FredM

From: Eastleigh, Hampshire, U.K. ................................... Fred Mundell. ................................... Electronics Engineer. (Primarily Analogue) .. CV Synths 1974-1980 .. Theremin developer 2007 to present .. soon to be Developing / Trading as WaveCrafter.com . ...................................

Joined: 12/7/2007

"The theremin is designed to be played without touching the antennae, dewster! Thus it's not a design problem, but the user's fault if he doesn't touch a grounded part, i.e. the front panel, to discharge himself before touching the antennae, though. Such simple precautions are (IMHO) self-evident." - Thierry

Sorry Thierry - but I completely and utterly disagree with everything you say here! Good electronics should cater for all likely reasonable "abuse" the user can subject an appliance to - touching an antenna when the instrument is grounded through even a "permanent" audio connection lead (even if not powered) without prior discharging of static they have unknowingly accumulated IMO MUST be regarded as an extremely likely occurence - even for the most careful of users!

"Couldn't you put an insulating sleeve on both the pitch and the volume antenna?" - Gibarian

Yes - I think this is a good idea for many reasons - it will also probably somewhat reduce ESD risk.. But it cannot substantially reduce the risk - One can easily get 12kV (12000 volts) or more charge on an insulated human, and this will spark across standard sleeving.

But, to me, this whole issue is completely absurd! Its SO EASY (and cheap - certainly less than $5 for full protection) to fit the required protection if one does this at the design phase that, IMO, neglecting to do this, and risking failure of instruments one supplies to customers, is utterly inexcusable..

Probably grossly incompetent and Utterly and completely inexcusable! - Perhaps the only excuse being the vintage of the design, when attitudes to ESD were more lax - but these days there is absolutely no excuse! - And for something like a theremin which has a high probability of being subject to direct ESD discharge into a high-Z antenna and sensitive circuitry, not providing simple protection with a neon or discharge tube was bad - even in the '60s!

I know - critisising anything Bob Moog did is "dangerous" - He was a brilliant designer of low power analogue and synthesis circuits - but IMO wasnt any genius when it came to good safety / reliability practices, particularly with regard to power supply and ESD.. The real disgrace, IMO, is that modern designers at Moog who must have been exposed to more ESD awareness than Bob was, have done nothing to correct the risk.

Fred.

"

Electrostatic discharge (ESD) costs the electronics industry millions of dollars each year in

damaged components, non-functional circuit boards and scrambled or missing information. ESD

can occur in the manufacturing, shipping, receiving, and field handling of integrated circuits or

[computer] Circuit boards with no visible signs of damage. A malfunction in these components or boards

can occur immediately or the apparatus may perform for weeks, months, or even years before an

unpredictable and premature breakdown causes a field failure.

" - Intel

And an antenna without ESD protection is effectively the same as having the board exposed - in fact, its worse - because this board is deliberately grounded, and a large area (the antennas) wired to it waiting to be touched!

 

Posted: 1/22/2014 9:44:49 PM
FredM

From: Eastleigh, Hampshire, U.K. ................................... Fred Mundell. ................................... Electronics Engineer. (Primarily Analogue) .. CV Synths 1974-1980 .. Theremin developer 2007 to present .. soon to be Developing / Trading as WaveCrafter.com . ...................................

Joined: 12/7/2007

 

"Out of that, there is my ashtray hanging in the loop for most of the time... ;-)" - Thierry

Switch to E-Cigs (or an E-Pipe)! .. No ashtray,no ash,no toxic smelly output for others to breath, no monoxide - You get whatever flavour you want and however much nicotine you choose (if you mix your own "juice") .. You can "vape" in a telephone booth with another person in there with you for 3 hours, and they will get no toxins other than about the same quantity of nicotine they would get from eating one tomato! ;-)

Fred.

Posted: 1/26/2014 1:28:09 AM
Bob Klips

From: Columbus Ohio

Joined: 1/17/2014

Progress Report (of sorts) on my static-zapped Theremin (Moof EWS). SPOILER ALERT: it still doesn't work. Well I took everyone's advice I got a socket for the installation of the amplifier LM13600 that came in the mail today. Removing the old IC and installing the new socket was a little rough on the circuit board I guess because when I got it all together it was totally silent. This time even shorting VCA OUT to GROUND didn't do anything. So I spent several hrs checking continuity and discovered that pin 12 and R30 and D5, which the wiring diagram shows as being all contiguous, were not in fact connected. The board circuitry that apparently connects them runs obscurely beneath the IC and looks a bit delicate; it isn't clear exactly what I messed up so I just added a jumpers from pin 12 of the IC to R30 and D5. Now it works, sort of. Problem: the loudest volume is low, about 1/4 as loud as the volume when VCA OUT is grounded, and the response is odd, with a "zero zone" like the frequency coil has...it doesn't seem right. What I'm wondering is whether tuning the slugs will fix the volume problem, or whether something else is going on. Plus, since I got this used, I don't have the magic tool for tuning the slugs' I imagine I could fashion something, or pick one up at Radio Shack? If anyone has any insights it sure would be appreciated. Thanks.

Bob Klips

Columbus, Ohio USA 

Posted: 1/26/2014 9:35:43 PM
Cephus

Joined: 1/26/2014

I just completed construction of the modern Jaycar Theremin.  Upon completing the tuning procedure, I was enjoying learning how it worked in controlling pitch and volume. 

I walked away from my electronics workbench for a few minutes.  I must have built up a good charge upon returning.  Making more noises, I touched the pitch antenna with an audible "pop" and a sensation of a static shock.  My poor Theremin fell silent. 

Upon checking voltages, the volume oscillator still seems to be running.  I still need to verify the master oscillator.  I'm guessing it took out the 2N5484 FET in the pitch oscillator. 

While I have no doubt I can fix it, I'd like to ensure this doesn't happen again.  A simple NE2 neon bulb across the volume and pitch antennas to ground should offer "some" protection.  The NE2 breakdown is about 70 volts.  Has anyone tried a simple form of protection such as this?

 

Posted: 1/26/2014 10:12:37 PM
Thierry

From: Colmar, France

Joined: 12/31/2007

These neon bulbs offer good protection. But they add capacitance. In theremin circuits without linearization coils (Jaycar, B3, etc.) they may be connected directly between the antenna connectors and ground. But in theremin circuits with linearization coils, they should rather be installed behind the coils to prevent de-tuning of the antenna series resonant circuit. In the Etherwave circuit on the volume side, a good point is between L8 and L7, so that the discriminator circuit is protected, too.

Posted: 1/26/2014 11:52:48 PM
FredM

From: Eastleigh, Hampshire, U.K. ................................... Fred Mundell. ................................... Electronics Engineer. (Primarily Analogue) .. CV Synths 1974-1980 .. Theremin developer 2007 to present .. soon to be Developing / Trading as WaveCrafter.com . ...................................

Joined: 12/7/2007

Yes, I have used neons on all my theremins.. But am switching to the Bourns parts

On page one of this thread (1/18/2014 12:59:31 AM) I started going into detail about ESD protection.

IMO, Neons are not enough - but they are a good start in the right direction, and probably the simplest basic protection without complications.

The Bourns discharge tubes have lower (and standardised) capacitance of < 2pF and are better suited to antenna connection on equalized theremins - But Thierry is right - even a 1pF extra capacitance on the antenna could substantially alter the operating point and therebye the linearity - I suspect that if you know what you are doing (moving the wire away from the foil for example) you could compensate for this added capacitance - but I am no expert on the EW.

I disliked putting discharge tubes down-stream from any component, but can see the rationale in Thierrys suggestion - my fear is that effectively discharging through the inductors puts these parts at risk - ok - the risk is probably smaller than for most other components, and might not be worth bothering about - But IMO if one got a Bourns tube with 1.5pF, and could compensate fot this 1.5pf by some means, that would be better..

Fred.

You must be logged in to post a reply. Please log in or register for a new account.