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Cold Measuring Information
Cold Measuring Components within Amplifiers and other Audio Equipment

Please DO NOT try these repairs yourself unless you have some in depth knowledge of Electronics.

Most Analogue Audio Units can have High Voltages and Currents flowing and will possibly electrocute you if you touch across anything you should not.

As always - DO NOT try to turn on any electronic unit where it previously sounded distorted or has blown fuses without firstly taking a good look inside!

Visual inspection is the first action.

Cold measurements of almost all components with an old AVO style meter are essential - other repair technicians like to use modern digital meters - I use them too - but NOT for Cold Component Fault Finding!

Put the Avo on the first DC Ohms setting.
Measure Diodes both ways round - the gate will show medium resistance - with the test leads the other way round - almost nothing.
Bridge Rectifier Diodes (with 4 legs) are similar but with extended resistance through the multiple gates.

Transistors - similar to Diodes but with 3 legs of course.
Caps - Electrolytics will give a kick with residual power - then eventually read almost open circuit. The dreaded Tantalum Caps will show the same but with less of a kick (size dependent).
Most other Caps should read near to open circuit.

For more in depth information about cold measuring with an Avo Meter have a look at {this interesting Web Page}.

Knowledge of the circuit is important as measuring one component whilst other bits are still in circuit will give you false readings.

Short or near Short Circuits deserve full investigation.
Avo Meter
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