ME1 – Magic Eye Organ & Winker Kit

Available at my eBay Store:

Rev A (Dec 10, 2020) – Component value change to C7 & L1. Only applies to kits SOLD, on, or after Dec 10, 2020. If purchased before Dec 10, but shipped afterwards, you have the pre-Rev A kit. C7 was 470pf, now 1000pf. L1 was 2.2mH, now 4.7mH. Changes are required, to properly work with a TRUE LM358 chip. All prior kits were shipped, with IC marked LM358, but were actually a superior part. Possibly a MC34072, but restamped LM358. Not everyday, that the Chinese restamp a superior part as an inferior one !

(click on Photo to view video, in operation)


This is a simple kit, designed to demonstrate side view magic eye tubes. Its pre-jumpered to act as a light organ, and has its tube socket pre-wired for the EM80 or EM81. The audio comes in the on-board microphone, and modulates the eye’s shadow. It can be re-jumpered for the EM84 or EM87 eye tubes. Plus it can also be re-jumpered to act as a simple winker, ignoring incoming audio.

Its powered from 12VDC, needing a minimum of 500mA. 12VDC 500mA (0.5A), 1A, or 2A wallcubes, with 2.1mm coaxial plugs and a center positive pin polarity.

The Kit is shipped WITHOUT a tube, which you need to purchase separately. I DO NOT stock these tubes.

When you finish assembling the kit, it should look as follows:

(click on photo to enlarge)


The Circuit:

Below is the schematic of the board:

(click on drawing to enlarge):

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The circuit comes in two sections, based around a jelly-bean LM358 dual op-amp. One of the IC’s op-amps, is used to make the switching supply, that steps up the 12V to ~180VDC. The LM358 is a pretty slow chip, so the oscillating frequency is low, at a few KHz (~5KHz). Its a simple boost-supply that pulses a simple inductor (L1), to generate high voltage pulses. Instead of a large power FET, a common 2N7000 FET is paired with a MPSA42, to perform the same function. Both transistors come in the common TO-92 package. The 2N7000 is relatively fast, but only rated for 60V. The MPSA42, while slow, is rated to withstand as much as 300V. This pair, as hooked up, does the job of a higher voltage rated MOSFET. Regulation, is done by the voltage divider R14 & R15. when the voltage at the common node (share between R14 & R15) exceeds, the nominal voltage at U1-6, oscillation stops, limiting the voltage to ~180V. D3 keeps the divider out of the circuit, when the HV is too low. Also two simple 1N4148 small signal diodes are used (in series) as the HV rectifier. Though common and inexpensive, they are very fast switches, as 4nS reverse recovery. Your other common diode, the 1N4007 (1000PRV, 1A – NOT used here) can only switch at a crappy 30uS (30,000nS), hence not suitable for switching supplies !

The other half of the LM358, is prewired as an amplifier with a gain of ~200, set by R7 & R6. It takes the audio, from the microphone and boosts it up to several volts (peak-to-peak). That amplified audio is then feed into a network, made of D1, D2, C5, C6, and R16, to create an envelope ranging from 0V to ~-10V, with a time constant of ~50mS (0.05sec). This signal usually drives the grid (G1) of the eyetube, varying the shadow, in coincidence of the ambient audio. Hence, a light organ.

The alternate wink function, can be used, by cutting the existing pre-jumpering, and adding R21 to the circuit (by jumpering J6). This turns the amp, into a low frequency oscillator. The frequency determined by R7 & C3. R6 being less than 1% of R7 does not effect the circuit. J3 is also re-jumpered to connect the eyetubes grid (G1), to pin 2 of  U1, where a slow (~1Hz or less) triangle wave is now present. Since this wave is positive, the cathode of the eyetube needs to be biased, more positively above the grid. This is done by re-jumpering J4.

The Build:

Below are the parts lists and assembly drawings, for this kit:

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(click on the list, to enlarge)

These are the parts that will come with the kit. Not included, are the 12V wallcube, the eye tube, parts for J2, J3, J4, J5, & J6. If you intend to use this kit as a light organ with either an EM80 or EM81, those jumpers are to be left, as is. re-jumpering, is only needed if an EM84 or EM87 tube is used, or if the winker function, is to be used.

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(click on assembly drawing to enlarge)

Look at the assembly drawing, for assembly order, and jumpering, if needed. just to remind you that this board is PRE-JUMPERED, an additional PRE-JUMPERED drawing has been provided. On this drawing the back side (solder side) of the board is shown, and cuts are to be made TOO, if you wish to alter function (winker), or use an EM84 or EM87:


(click on drawing to enlarge)


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