ACS 2 Voice Scrambler Repair and Teardown

I bought this ACS 2 voice scrambler as surplus. One handset arrived damaged, so I repaired the mechanical and electrical connection before opening both units for comparison.

Construction

Each handset contains an audio board, a larger logic board, controls, a microphone, an earpiece and the wiring between them. The boards use through hole parts and socketed integrated circuits. This makes the unit practical to inspect and repair.

The two handsets exchange an audible startup sequence before the scrambled audio path is ready. The video records that exchange. It is useful for timing and signal study, but the sound alone does not reveal the scrambling method or its security.

A sensible way to study it

1. Record the model, board markings and connector wiring.
2. Check supply rails and audio paths with the unit disconnected from any radio.
3. Feed a known audio tone into one handset.
4. Record the signal before and after each analog stage.
5. Compare the two units to separate normal design features from faults.

Older voice scramblers often traded speech quality for simple hardware and narrow radio bandwidth. A device of this age should not be treated as secure private communication. Its value here is historical electronics, audio signal processing and repair practice.

Testing should use a cable, audio load or permitted laboratory radio link. Do not connect to a service or frequency without authorization.

Project photographs

Project videos

3D Touch Bed Probe Teardown

I opened a 3D Touch bed probe to see how a small retractable contact sensor works. This unit is a BLTouch style clone. The photographs document the clone itself, while the genuine BLTouch documentation is a useful reference for the operating idea.

Inside the probe

The main parts are a plastic push pin, a small coil, a magnetic moving part and a controller board. The coil changes the position of the pin. The electronics read the pin state and provide a separate trigger output to the printer controller.

This arrangement is different from an inductive probe. It touches the bed, so it can work with glass and other nonconductive surfaces. It also avoids a normal exposed microswitch. The probe still depends on a straight, clean pin and a rigid mount.

Signals and power

A BLTouch type system normally has two interfaces. A servo style control signal commands the pin, and a second output reports the probe event. The genuine BLTouch uses a Hall sensor and a solenoid. ANTCLABS specifies less than 15 mA in standby and a short pulse below 300 mA while the pin moves. Those values belong to the genuine device and should not be used as guaranteed ratings for a clone.

Wire colors are not a reliable pinout across clone versions. Check the exact board documentation and verify ground, 5 V, control and trigger with a meter before connection. A reversed supply can damage both the probe and the printer board.

Practical checks

1. Mount the body square to the bed and keep the pin vertical.
2. Move the pin by hand only when power is off.
3. Run the printer firmware self test before homing the Z axis.
4. Keep one hand near the power switch during the first homing test.
5. Repeat the probe test at one point and compare the spread before trusting a full mesh.

The ANTCLABS BLTouch technical page explains the genuine sensor, its signal timing and its current requirements.

Project photographs

Tektronix TDS3054 Repair

This Tektronix TDS3054 had a dead input channel, a failed capacitor and several brittle plastic parts. I repaired the electrical faults and returned the oscilloscope to operation.

Instrument specifications

Tektronix specifies the original TDS3054 as a four channel, 500 MHz oscilloscope with a 5 GS/s sample rate on each channel and a 10,000 point record. The TDS3000 family also includes 100 MHz and 300 MHz models with lower sample rates.

The models share many mechanical and software parts, but their published bandwidth and sampling hardware are not all the same. Each model should be tested against the bandwidth and sampling specification printed for that model.

Dead channel

The dead channel traced to a bad solder joint. I cleaned and repaired the joint, then compared the channel with the working inputs using the same source, cable, impedance and vertical settings.

A complete channel test should cover DC offset, gain, noise, input impedance and several frequencies. A waveform on the screen proves basic operation, but bandwidth needs a calibrated source and a measured amplitude response.

Capacitor and mechanical work

I replaced the failed capacitor with the correct capacitance, voltage rating, temperature rating and polarity. Electrolyte residue must be cleaned because it can continue to damage copper.

Some plastic clips had become brittle with age. The case should be opened in the order shown by the service manual and without forcing hidden tabs. Broken internal supports must not be left where they can touch the power supply or fan.

Checks after repair

• Inspect the mains input, protective earth and internal shields.
• Confirm every power rail before reconnecting expensive boards.
• Run self calibration after warm up.
• Compare all four channels with a known source.
• Have the instrument calibrated before using it for specified accuracy.

The Tektronix TDS3000 data sheet gives the specifications for each original model.

Project photographs