My question is, what are we trying to accomplish with the Zapper? Are we trying to "iron" the felt, remove moisture, "singe" the felt (smoke the bushing), or drive out the vertigris? Even if you use two soldering irons, that pin conducts heat very well, and you're going to heat the wood in the birds-eye anyway. Whatever the idea, you don't want to ruin the bushing in the process. This discussion is probably in the archives somewhere. It is not something that should be done on a quality instrument, as the result is usually a very loose flange pin fit. It is a down-and-dirty fix when you don't want to, customer can't afford to, or otherwise aren't going to fix it the right way. Do I have one? Yup. Do I use it? Yup, but I don't expect to get 4-6 swings consistently. Having said that, I have thought of ways to regulate the heat produced, as suggested by Jeff. The trick is to have the timer begin when the probe and pin are a complete circuit. It's not always easy to make the probe contact the center pin to complete the circuit because the pin is often buried in the bushing. A foot switch would work, with a separate circuit for the power source and a continuity checker. You would connect the probe, and verify the circuit was closed by using the continuity checker (a buzzer perhaps), then press the switch. The continuity checker would then disconnect and send power to the probe. I've built several of these, and one problem I had using a doorbell transformer was that the transformer has a built-in safeguard that prevents a fire in case there's a short circuit. Guess what? The Zapper is a short circuit device! After a few uses, the transformer gives up. What is needed is a current limiter (resistor) in the circuit. The formula is E=IR. If you have constant voltage (E), your current (I) will vary inversely with the resistance (R). Another formula is for power: P=IE. Power (P) is current times voltage. If your transformer is 12 volts, and you have a resistor of 120 ohms, you will get 0.1 amp of current (divide 12 by 120). Then, multiply 0.1amp times 12 volts, and you get 1.2 watts of power. Your resistor must be able to carry 1.2 watts (most common resistors are 1/2 watt). A potentiometer (variable resistor) in the circuit will work to vary the power output. If you had a 12 ohm resistor, you'd have 1 amp of current (careful here- can your transformer handle 1 amp?), and you would have 12 watts of power (12 volts times 1 amp) and you'd need a large resistor capable of 12 watts of power. Constructing an electronic device with enough complexity to survive constant use is a little more complicated than it may appear. A Zapper made of a doorbell transformer is extremely crude. There may be some potential in a more carefully designed circuit to accomplish one's desired purpose. Purchasing a constant current device (such as is suggested) seems a little overboard, but there is certainly room for further investigation and experimentation. Now, where is my pin extractor... Paul McCloud KQ6FL San Diego > [Original Message] > From: Jeff Deutschle <oaronshoulder at gmail.com> > To: <pianotech at ptg.org> > Date: 03/30/2009 4:27:15 AM > Subject: Re: [pianotech] Build a Zapper > > Rather than a simple transformer a “Constant Current Source” ( > http://www.ietlabs.com/IET/VI-700.html ) would be better. The device > puts out whatever voltage is required (up to a point) so that the > amount of current (which is what produces the heat, not the voltage) > is constant regardless of the resistance between the probes and the > pins. Then the amount of heat that is applied can be regulated by how > long the circuit has been made rather than how much smoke is produced. > I haven’t looked, but I am sure these come up on E-Bay, or a circuit > with an adjustable timer could be constructed without too much > trouble. A Ham radio buff could probably do it easily. > > On Sun, Mar 29, 2009 at 6:24 PM, pgmilkie at juno.com <pgmilkie at juno.com> wrote: > > Copy and pasted this post a few months ago by Michael Magness. > > > > > > > > We used to build our own here in our little corner of Wisconsin and it's not all that difficult. > > > > All of the necessary parts can be acquired from a hardware store or home center. A doorbell transformer 10 to 14 volt is sufficient, some AC cord and an AC plug for the AC side of the transformer. Some DC wire about 10 gauge is sufficient and some connectors both the crimp kind for splicing 2 ends together and the round ended kind to bolt through. A small piece of masonite, hardboard or even pegboard about 1/2" X 3/4" and a large tweezers and lastly a small diameter non-metallic bolt and nut. > > You begin by disconnecting the two arms of the tweezers, you can also make the tweezer arms from old hack saw blades cut in half, grinding one end to a point and bending it over. > > Clamp the tweezer arms with the masonite or whatever you choose to use, between them and drill a hole large enough for the small bolt to fit through. > > > > Attach the AC cords to the approriate ends of the transformer and the plug to the end of the cord. (I used an old lamp cord with a pre-molded plug) Attach the 10 Ga wires to the DC side of the transformer, attach the round ended connectors to the open ends of the wire and attach those ends on either side of the tweezers with the bolt and nut and washers if necessary. > > You might want to mount it on a small board for portability and ease of storage. > > > > Plug it in and lightly touch the ends to one another if you see a spark you have succeeded, if not check your connections. Remember it is important that the two "sides" of the "circuit" or tweezers are insulated from one another until they contact the center pin > > > > When using this device do not hold it on the pin ends longer than a few seconds, they heat up VERY quickly! > > > > Don't ask me how I know! > > (grin) > > Mike > > > > I intend to live forever. So far, so good. > > Steven Wright > > > > > > Michael Magness > > Magness Piano Service > > 608-786-4404 > > www.IFixPianos.com > > email mike at ifixpianos.com > > > > > > ____________________________________________________________ > > Get vinyl fencing options and products. > > http://thirdpartyoffers.juno.com/TGL2141/fc/BLSrjpTGbADH4bP8vFVSS30OvC1vhFcw HphjFzb0DxRPK9Cg0Bi5m0JbCLW/ > > > > > > > > -- > Regards, > Jeff Deutschle > > Please address replies to the List. Do not E-mail me privately. Thank You. >
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