Fig, 8t Bottom view of Fairchild gate and flip-ffop IC's, Note: Pin 8 of all modules goes to +3,6 volts; pin 4 to ground, bearing and if a flexible jumper does not bypass this bearing there can be erratic operation. Some of the key paddles designed for use with electronic keyers have considered this problem; others have not.
Trouble shooting if required, is simple. An ordinary multimeter may be used effectively. When a circuit point is supposed to be low, it should read not more than about +0.18 volts. High level may be anywhere between about +0.95 volts and the full supply, depending on circuit loading. The use of a shielded enclosure is strongly recommended. These logic circuits are extremely fast, and only a hundred millivolts of RF may be sufficient to send the keyer on a wild generating spree. 1 he ordinary aluminum box is quite effective. The use of a pair of 0.0 I \ii discs at the dot and dash input terminals is useful in case of stray RF, Also, use a small bypass in the output wire to the external circuit. If erratic dash operation is observed but with normal dot generation and memory, connect a 100 pf disc between 1 iie output of G-6 and ground. This reduces the very small spike which may result during dash generation when F-5 goes high, triggering F-6 to low. If the spike reaches F-4, it will clear it and terminate the dash.
The IC's used here are specified by Fair-child for operation between 15° and 55° Centigrade (59 to 131 degrees F). The keyer dissipates very little heat by itself (about 450 milliwatts), but the effect of heat generating equipment nearby should be considered.
■ fie Micro-Utiimatid is designed to comply with die loading rules speciiied for the lC?s used; therefore, it may be expected to show the relial ility of operation associated with integrated circuits. The author's kever has been running continuously for four months without a sign of problems. This is the eleventh type oJ keyer which I've built and it's a honey, the smoothest running and most dependable keyer yet. The real test comes during a contest, and I his keyer leaves nothing to be desired.
1/2 s99142s gate
\/Z 3991428 GATE
Schematic of monitor oscillator.
This simple scope used inexpensive high voltage transistors instead of conventional tube-type deflection amplifiers.
Teleprinter circuits are admirably suited for transistorization, as indicated by the number of recent transistor TU designs. These ["Us have had to use meters or tuning eyes for tuning indicators due to the difficulty of designing scope deflection amplifiers.
This article will describe a simple (nearly) all transistor X-^ oscilloscope, designed for Rrl V tuning, but suitable for general X-Y plotting and frequency comparison work. It incorporates a unique blanking circuit to dim any undeflected spot.
Cathode ray tubes require such large defection voltages that transistor drivers have
Tom, former WiOEY and W1SMY, is an electrical engineer (USEE, MIT) for the Tappan Company; he designs microwave ranges. Tom has written many articles in 73, mostly on RTTY.
been uneconomical and unpractical. Recently several 300 volt silicon transistors have become available to reverse this situation. They are ideal for scope deflection amplifiers. The RCA 40264 ($1.21) uSes a small diamond case5 with non-standard leads. The Industro Transistor TRS-301-LC uses a standard TO-5 case and was used here. Either will work*
One of the photos shows an excellent 300 volt p-p sine wave at just below the amplifier's clipping level This is enough voltage to deflect almost any 2, 3, or 5 inch CRT operated at moderate accelerating voltages.
The amplifiers are quite conventions except for the 300 volt 13+. My particular scope obtained full deflection with inputs of only 0.3 volts (RMS) vertical and 0,5 volts horizontal. The input impedance varies with the gain
* iNpUSTHq TRS-30I-LC
r 1600V IW
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