Ramsey Electronics manual Congratulations, Testing the SS70A

ˆ51. Install C18, the last 10 uF. Watch that polarity!

ˆ52. Install VR1, the 7805 voltage regulator. Orient it as shown in the parts diagram, with the metal back facing edge of the PC board as shown. This component provides a stable source of 5 volts to the MX128 IC chip, and throughout the speech scrambler.

CONGRATULATIONS

You have just completed your SS70A speech scrambler/descrambler unit. Take a well deserved break now. Give your eyes a rest. When you return, be sure to check over your work on the entire circuit board.

TESTING THE SS70A

Before we dive into testing of the SS70A, let’s review the various connections that can be made to the unit. When we’re ready to actually test and hook-up the scrambler, we’ll have to determine what configuration we need for our application.

The SS70A requires a clean source of power from 9 to 15 Volt DC which is connected to power input jack J5 (center pin is positive). Current requirements are typically 250-500mA, which means a decent battery set (C or D cells) or good quality power supply may be used. If you’re going to use a cheapy wall adapter, be sure it is good for the required current and is well filtered or you can expect lots of hum and noise.

Audio connections for the unit are made through the four 3.5 mm phone jacks. On the receive side, either line or speaker level inputs may be selected by S3. Output level is dependent upon J4 position. The transmit connections are intended for microphone level use.

Line level is commonly used for amplifier inputs, i.e. tape, aux “in” on your Hi-Fi or stereo tuner/amplifier. “Line level” is just a term that describes the un-amplified audio signal (typically 1 volt peak to peak). It is generally used for tape deck or earphone output circuit levels.

“Speaker level” is just what its name implies - an audio level sufficient to drive a speaker. Remember, the better the speaker connected to the SS70A, the better the sound quality.

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