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3rd Aug 2006, 12:50 pm | #1 |
Rest in Peace
Join Date: Mar 2006
Location: N.W. Oxfordshire(Chipping Norton)
Posts: 7,306
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AUDION 'SILVER NIGHT' Valve Amplifiers
Few people may have come accross,or even heard of, these Valve Amplifiers(British Made)but I was asked if I could repair one recently, which suffered from mains hum pickup. The Power supply is a conventional Bridge Rectifier Circuit, using 4 x 1n4007 diodes, with a resistor/capacitor filter circuit using 4x 100uf or 220uf 400v Electrolytics and a 100R 7Watt Ceramic resistor(Circuits of the power supply and amplifier can be downloaded from www.audiokitmania.com) though variations exsist, and component values differ in some units. The problem was traced to faulty reservoir & smoothing capacitors, and, having replaced all four, not a trace of hum remained.
Incidentally these amplifiers use 2 x 300B Power Triodes(originally designed in the late 1920s) in a class A circuit, and produce about 7 watts RMS into a 4 Ohm load |