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Help with (self)serviced Revox amplifier
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<blockquote data-quote="Steerpike" data-source="post: 129727" data-attributes="member: 807"><p>The PCB trace ends at the component in a little disc/pad (looks like a tennis racquet). The strip of copper can crack where the thin linear trace joins that pad: The pad itself separates from the board when resoldered, but the linear trace stays glued. When the component (transistor, capacitor) is physicallu stressed, the pad flexes with it, but the linear strace stays stationary - then something breaks!</p><p>It's very difficult to see, but if you wiggle the components while watching their solder pads, any where the pad itself moves, that is a suspect pad. Putting pressure on the pad while the amp is operating may fix the connextion temporarily. But I suggest a wooden stick as some amps may have about 150 volts on their output transistors and that can be a bit of a shock to bare fingers.</p><p></p><p>Are you hearing a 'humm' or a 'buzzzzz'? Is anything getting unusually hot?</p><p>I see from those two boards that one still has a gold Rifa cap on it - very, very bad capacitors those, it must come out. </p><p></p><p>Those 4-pin capacitors CAN be bought in SA. I located them for my B285, but they are quite costly - I think around R250 each - depending on the brand/quality and size. RS-components have some, and I think Communica in Pta also had. Panasonic and Aerovox are the brand names that come to mind.</p><p></p><p>For my B250 which needed even bigger 4-pin ones, I bought the Lelon 2-tag style for audio and made an adapter board.</p></blockquote><p></p>
[QUOTE="Steerpike, post: 129727, member: 807"] The PCB trace ends at the component in a little disc/pad (looks like a tennis racquet). The strip of copper can crack where the thin linear trace joins that pad: The pad itself separates from the board when resoldered, but the linear trace stays glued. When the component (transistor, capacitor) is physicallu stressed, the pad flexes with it, but the linear strace stays stationary - then something breaks! It's very difficult to see, but if you wiggle the components while watching their solder pads, any where the pad itself moves, that is a suspect pad. Putting pressure on the pad while the amp is operating may fix the connextion temporarily. But I suggest a wooden stick as some amps may have about 150 volts on their output transistors and that can be a bit of a shock to bare fingers. Are you hearing a 'humm' or a 'buzzzzz'? Is anything getting unusually hot? I see from those two boards that one still has a gold Rifa cap on it - very, very bad capacitors those, it must come out. Those 4-pin capacitors CAN be bought in SA. I located them for my B285, but they are quite costly - I think around R250 each - depending on the brand/quality and size. RS-components have some, and I think Communica in Pta also had. Panasonic and Aerovox are the brand names that come to mind. For my B250 which needed even bigger 4-pin ones, I bought the Lelon 2-tag style for audio and made an adapter board. [/QUOTE]
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Help with (self)serviced Revox amplifier
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