Non-Metalic Inductor Coil Adjustment Tool

[JAC_101]

Hello,

 

I am looking for non-metalic tools for adjusting inductor coil ferrite cores and variable capacitors.  These look like screw drivers but are not made of metal.  These were common years ago when televisions and radios could be tuned.  I am looking to use the tools and or buy a set for my future use.  If you have them then stop by the Tuesday night meeting and we can talk.

 

As background, I am building a theremin and need to adjust the circuit. 

 

Thank you.

(Director of Legal Evil)

[#]

http://www.ebay.com/itm/1set-Plastic-RF-IF-Core-Adj-Screwdriver-4pcs-complete-/140391623405?pt=LH_DefaultDomain_0&hash=item20affe2aed

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[Tim Gillespie]

Tell me more about this theremin, here is the one built: http://wiki.lvl1.org/Forbes_Tube_Theremin

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[JAC_101]

I am building the theremin from website: http://www.strangeapparatus.com/Theremin.html

 

It uses colpitt oscillators.

 

The issue I am having is with the Volume Variable Oscillator Circuit.

It does not seem to behaving as described.  The potentiometer has almost no effect and the antenna does not have an effect unless actually touched.

 

The problem could be circuit layout and interference but the other circuits are layed out the same and are working.

I have had the circuits on a scope.

I will be seperating the circuits from a common board and tuning them again. 

 

I'll also check with the local tv repair for the tools.

 

The ebay link is greatly appreciated.

 

ANALOG is NOT DEAD.

 

Director of Legal Evil.

 

[Tim Gillespie]

If I recall, that sounds similar to the problem that I have with mine.  Adjusting the variable capacitor in the bandpass tank circuit would effect the amplitude of the volume oscillator.  I tested the filter by itself and the oscillator by itself and they worked fine and I could tune them both as they should be, but the two were interacting such that I wouldn't get volume control until touching the antenna, because the oscillator amplitude would change due to some effect other than the intended attenuation from the filter.

 

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[stea...@gmail.com]

Sounds like a job for the 3-d printer!

Thanks,

Dan

Sent from my iPhone

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[JAC_101]

Small fine tipped tools are best when ceramic.  The 3d printer is likely to produce a breaking stick.  There tools used to be made from filed down bakelite and such.  They are not intended for high torque but must be solid in design.

[2600]

There is an economic decision that underlies the choice between a
plastic and a ceramic too tip.

Inevitably, the friction to turn the threaded adjustment slug will
reach the breaking point of one or the other.

The plastic tool will break off at the tip. The remedy is the cost of
another tool, and a dental pick to tease the broken plastic back out
of the slot in the adjusting slug.

The ceramic tool will not break so easily. The brittle ferrite tuning
slug WILL. Some types will then press outwards against the inside of
the coil form when you try to turn it after this. Kinda like the
centrifugal clutch in a go-kart. Seizes the slug against the interior
surface of the coil form. The remedy depends on the construction of
the adjustable coil, as to how the cracked slug may be removed, let
alone identify and obtain a new one that fits and has the correct
materials recipe. Those tuning slugs are not all made from the same
material. Many of the radios we service have a double-ended slug,
accessible only from the top once the coil is soldered to a pc board..
Unsoldering the coil from the pc board exposes the undamaged end of
the slug. Turning it (carefully) to exit the bottom, removing the
fragments, reinserting it from the top and resoldering the coil to the
pc board is a familiar procedure here. Simply turning the slug too far
in the clockwise direction can cause it to seize in place.

The Ebay kit shown does not appear to have a 1.3 mm ( or so) flat tip
visible.

Good chance that the "G-C" brand type 9440 tool from Peerless
Electronics (502) 637-7677 will fit the slot in your coils' tuning
slugs. It's the sacrificial-plastic type, so buy more than one.

73

[2600]

Just a P.S. on this: Don't know the size tool your coils need. Did
turn up a a few hits on "ceramic alignment tool" on Ebay. Bought a
couple of the 1.3 mm size we use a lot for about four bucks each. Size
matters. Too small, and a ceramic tool will put uneven stresses on the
surfaces of the slot and risk splitting it. Too large is self-
explanatory. Just won't engage the slot.

Wouldn't hurt to have an estimate of the adjusting slot's dimensions.

73

[JAC_101]

Slot size is 2.5 by 0.5, actually it is cross/Phillips type.

This particular tuning is for a variable capacitor.
It is one with underside access, so I mounted it upside down to avoid drilling the circuit strip board. Stop by Tuesday and I'll show you the item and maybe you can help me with a question or two.
I would appreciate speaking to someone who remembers the world was analog.

[2600]

Whups.. Missed this week's meeting. This is my intensive season at
work.

Seriously considered coming next week 2/5. But that's what I was
saying last week about today.

My favored tool for those has a narrow metal blade tip in a plastic
body. So long as the rotor side of the capacitor is at signal common,
the metal won't disrupt the setting when in contact with the slot.

The bottom of this page at Copper Electronics shows the three sizes
they (might) have on hand. Never hurts to call them and check stock
before dropping in on them.

http://www.copper.com/cart/advanced_search_result.php?search_in_description=1&keywords=ceramic&osCsid=0ed5a072429fa244a865d94dde39a8a6&x=9&y=4

In some circles they call me the Analog Retentive.

As in "Digital? Just what is "digital"?"

It's an abstraction we impose upon analog systems for our own
purposes.

73

On Jan 28, 10:05 pm, JAC_101 <cabrera....@insightbb.com> wrote:
> Slot size is 2.5 by 0.5, actually it is cross/Phillips type.
>
> This particular tuning is for a variable capacitor.
> It is one with underside access, so I mounted it upside down to avoid drilling the circuit strip board.  Stop by Tuesday and I'll show you the item and maybe you can help me with a question or two.

[Tim Gillespie]

Any progress on the theremin?  I could bring mine to soundbuilders tonight, perhaps we could get them both working, it sounds like we have similar issues.

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[Jose Cabrera]

Have discovered a few hints to problem. I will likely be there tonight.

It will require scope work but original design had a component value off.

The rest is just madness.

[Joshua Wilcox]

I bet the tv repair guy next door has one you could borrow for a second.

Sent from my iPhone

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[Sean McPherson]

I don't have a set I can lend out, but we use ceramic ones when working on our gear. They're pricy but useful. You can usually find them under 'alignment tool' (for old TV and radio sets, as mentioned) or under ceramic adjustment tools.

 

Plastic low torque ones only run a few bucks ( a la http://www.tecratools.com/product1120.html ) and the ceramic sets are about 10X but higher torque (a la http://www.stanleysupplyservices.com/product-detail.aspx?pn=416-925 ). They have 4-in-1 ceramic ones for under $40, sometimes $25. Aven's a decent brand for them, IMO.

 

Sean

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[Tim Gillespie]

Jose, did you have any luck with the switching diode?  Reading the description of the circuit that you built, it should work like mine does with a DC voltage biasing TR1:

"As the player’s hand moves away from the volume antenna, the frequency of the volume oscillator also moves away from the resonant frequency of the tuned circuit. This causes the DC bias at the base of TR1 to fall away and its collector voltage to rise."

It sounded like last night you were still getting an oscillating signal at TR1 only at a different frequency, instead of a DC signal.  Curious as to whether that was due to the diode.

[Jose Cabrera]

I replaced the 4.7pF caps with 47pF caps in the resonance circuit and it came to life.

The volume problem has a twist. I found this web sight

http://www.dogstar.dantimax.dk/theremin/thersens.htm

I'll be testing some other changes during the week including shielded cables to the antennas and separation of the circuits from a single PCB.

I replaced the diode but haven't tested it yet.

[Brian Wagner]

 Non-Metalic Inductor Coil Adjustment Tool sounds like a job for the Makerbot!

[Pat McCarthy]

Brian… this was asked and answered a LONG way back in the thread…   Keep up!

(Of course, I have NO CLUE what they’re talking about for the most part but…..]

 

 

 

Patrick McCarthy

 

T 502.476.9878

C 502.939.1756

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[Jose Cabrera]

Already suggested but small size tip and torque not compatible.

[Brian Wagner]

How about a nylon bolt and a few minutes on the grinder?

[Brad Luyster]

Or a large block of delrin and a few hours at the mill?

[Ben Hibben]

Give it to me and I'll bet I can grind it faster than that; seconds on the grinder.  :-)  Especially if I cna use my dad's.

Blenster

On Tue, Feb 5, 2013 at 3:07 PM, Brian Wagner <br...@tegrasys.com> wrote:

[dammitcoetzee]

I have a set of ceramic adjusters I got off deal-extreme. + and - . I'll bring them tonight.

[dammitcoetzee]

http://dx.com/s/ceramic+screwdriver

[Brian Wagner]

Just don't grind those fingers!

[Tim Gillespie]

I have my volume antenna working now with a range of about 12-14".  That isn't anywhere close to the range that the pitch antenna has, but that seems to be the nature of the design and I'm satisfied.  I ended up operating the volume oscillator at about 1.3 MHz using the original cap value from the schematic in the oscillator (I had a larger cap in there on monday in order to achieve 770kHz like the original designer, but his inductor must have been a much higher value than mine).  I also reduced the caps going to and from the LC bandpass from 15pF to 3.3pF and added a pot on the grid of the VCA to tweak the threshold.  I have attached a markup of the changes I made.

On Tue, Feb 5, 2013 at 3:07 PM, Brian Wagner <br...@tegrasys.com> wrote:

[Jose Cabrera]

I tested with the new diode. No real change. The web link I sent which identifies the frequency change rate with capacitance made me do a few calculations. And it seems that the large cap values adjacent to the antenna do overwhelm the small changes to the antenna capacitance. Your change of that value does match the sites logic for increased sensitivity.

I'll be testing a cap and inductor change to increase sensitivity while keeping the frequency close to the 440khz target.

I'll probably have everything tested out by next Tuesday.

[Lockadoc]

Bob and Tom show on 95.7 is talking about the Theremin this morning

Bill S

Sent from my iPhone