museum items
5Mhz Xtal
100Mhz Xtal
Accoustic Delay
10cm wafer
Magnified Image
Lead Frame and IC
Variable Capacitor
Old Carbon Resistor

Electronic Components

Crystal Oscillators

Crystal oscillators are extensively used in electronics for clock signal generation. Computer and clocks require accurate timing signals.  The piezo-electric effect can be used to generate an electrical oscillation due to small changes in crystal thickness when a voltage is applied. The pictures below show two crystal oscillators. The round one is in an evacuated envelope to minimise heat change which affects the frequency of the output. This crystal also operated in an oven which maintained the ambient temperature at 65°C.

The crystal shown lower right has been removed from its cover and can be seen supported by two wires connected to the rails on either side.


Charged Coupled Devices (CCD) have replaced vidicon image tubes. A CCD from a digital camera is shown in the next image. This is a close-up of the device which looks like a windowed integrated circuit (IC). The fine wire bonds connect to the IC packaging. The CCD 'chip' array is framed by logic circuits and manufacturers information around the edge.


In analogue colour television, the processing of the chrominance signals takes longer than the luminance. In order for them to be recombined with the correct timing a technique with sound is used to delay the signal.  The picture shows a thin glass plate with two piezo transducers attached. One is used to produce an ultrasonic acoustic signal, the other received the sound wave and reconverts it into a small electrical signal. As sound travels much slower than electricity, a delay is formed in the transmission.  I am guessing that the black globs of glue are for damping to prevent reflections and resonance of the glass.

This technique was also used as an early computing memory device where a sound wave could store information as it travelled down a wire to a receiver.

Chips with everything

This 10cm silicon wafer dates back to the early 1980's. The magnified image shows a close-up of some of the individual integrated circuits (IC) and one of the mask alignment images.  The third picture is of a IC lead-frame without encapsulation and shows how a 'chip' is placed for connection once cut from the wafer.

Cariable Capacitors

These are becoming rare as they have been replaced by electronic tuning with varicap-diodes. The variable capacitor was used extensively for tuning in radios. There are 4 variable capacitors in this unit.  Movable aluminium plates connected to the brass spindle can be moved in and out of the fixed plates in the housing. This varies the area of metal overlap. The two sets of plates do not touch at any point but the capacitance varies with the area of overlap.

Old style Carbon Resistor

An early solid carbon resistor is shown on the left, with a more common metal film resistor for comparison. These resistors used the same colour coding but were read differently. The body colour (violet) is the first figure followed by the end colour (green). The centre dot (orange) is the multiplier, and the gold is the tolerance as usual. This reads as a 75kΩ resistor. It actually measures 81k ohms which makes it out of tolerance.

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