Right handed Moog to a left handed - cannot tune properly...

The real question, in the context of this thread (as I see it) is:

If a (EW) theremin goes badly out-of-tune, what should its owner do? Should they attempt to re-tune the instrument (as per procedure detailed by Amos), or should they assume that "your" fault has developed, and send the theremin to you for repair ?

I would agree that a sudden, radical change in the tuning is more likely to indicate an actual 'fault' condition - But even so - If the theremin becomes unplayable, there is no real 'risk' in opening it up and attempting to re-tune it.. Worst case, these efforts will not fix the problem, and one will need to send the theremin for repair.. If one 'fixes' the theremin, and it does not stay 'fixed' for long, then one can send it for repair.... But, if one 'fixes' the theremin by re-tuning, and it stays fixed, one has a) saved money and effort by not sending the theremin away. b) Gained valuable hands-on experience. c) Has a theremin to play rather than having a theremin-less gap while the theremin is being fixed.

So I stand by my original advice.

You "accuse" me of not being "pragmatic" or (lol) "experienced" .. But you suggest that people having a tuning problem with their EW first take voltage measurements in order to determine whether Q9 has failed.. Now, there are some reading this thread who will find this advice useful, and for whom this could be a great help - BUT, the MAJORITY of people would not know one end of a multimeter from the other.. Most of these people could wield the plastic tuning tool and adjust the coils following Amos advice, but go into a state of panic at the idea of connecting probes to wires and taking measurements!

I feel that all the contributions to this thread have been helpful - Gordon's "CD on top" advice and link to Amos posting, My posting which I hope gave a reasonable overview of the science, so that rather than just adjusting the coils, the person had some understanding of what they were actually doing - and you posting which gave useful extended advice on a specific EW problem, and how to identify this.

All would have been nice, co-operative community activity.. Except that you felt the need to make utterly irrelevant personal comments about me.

And yes - despite your complimentary introduction[i] "@Fred: You are a genius on the theoretical field.."[/i] (despite the fact that nothing I had said was remotely "genius") what followed was, to my interpretation, nothing less than a needless snipe at my competence and experience.

I have been practicing in electronics for more than 40 years - I was probably an electronics hobbyist when you were still in nappies! I completed my first ICS electronics course at 14, and worked through the levels of technician, graduate engineer, design engineer, medical physicist, consultant, and technical director.. It is only my health which prevented me from continuing this career path.. When it comes to experience of electronic products (all aspects, through evaluation, design, production, certification, fault assessment etc) you are a grasshopper by comparison.. A good grasshopper - I deeply respect your abilities and on some levels you understanding if far superior to mine (I am particularly thinking about mathematics here) - but a grasshopper nonetheless! ;-)

It would be nice if, in future, we both refrain from any kind of personal remarks about the other.. We are both going to be appearing on the same threads - and when there is REAL technical disagreement then obviously we need (for both our benefit, and the benefit of readers) to air these.. BUT, IMO there was no justification whatsoever for your personal comments to me on this thread - they had NO technical merit WHATSOEVER.

Fred.

Sorry, between juggling work and gigs, I never have time to get on her. I don't know anything about electronics, but I am use to left handed theremins and playing a right handed one backwards.
Like everyone 45 minutes is wayh to long, ether direction.
I think everyone gave you expert advice and you should follow them.
But a truly left handed theremin, still tunes the same as a right handed one

Andy

@Fred: It was not my intention to offend you. It seems that you took my friendly affectionate teasing, a central element of French humor, the wrong way. Please accept my apologies. I'm aware of the fact that I use to be rather the theoretician while you spent your whole life dealing with "living" transistors and microprocessors. That's why I found the hidden self irony of my initial remark so amusing.You didn't - I'm really sorry!

Back to theremin circuits: My intention was to show a way how to diagnose directly the eventual root of a potential problem instead of trying to cure symptoms. Everybody may tune his coils and put CDs on the top of his theremin as long as he wants...

I just wanted to prevent people from loosing hours (as I did when I was first confronted to the Q9 problem) with trying to tune the oscillators without getting satisfying and long-term stable results. And, after fixing the "real problem", having to tune them once more, which is most times trying to come back towards the initial slug positions.

So I think still that a quick look on the circuit board revision and the eventual check of a single voltage may be the quicker and more direct way to healing the instrument.

[i]"@Fred: It was not my intention to offend you." - Thierry[/i]

Accepted, thank you.

Perhaps the fact that you write such perfect English makes me forget that you are French ;-)


Fred.