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DIY For Audio
Old Suitcase Turntable Amp Rescue
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<blockquote data-quote="marantz123" data-source="post: 1064030" data-attributes="member: 16849"><p>Thanks for the insight. A bit more detail is that the resistors serve to protect the rectifier when hot-switching occurs. An indirectly heated rectifier being switched off and on again while the cathode is still hot enough for emission can cause a rush of current flow which can exceed the guidelines (per plate). Even with the guidelines, the 6x4 was designed with a decent safety margin. The 150 Ohm resistor per plate in this design allows protection up to 200VAC per plate (effectively 400VAC peak-to-peak supply) according to the Sylvania datasheet. This equates to 1.3Amps per plate which is above the guideline, however considering that our plate supply is well below that, its within the 1Amp guideline per plate. The resistors are definitely important in this suitcase design, seeing that there isnt an AC transformer introducing some impedance in the supply to the rectifier. </p><p></p><p>Its still concerning what wattage rating of resistor is to be used here. </p><p></p><p>Out of interest, what is the wattage of the 150 Ohm resistors in the suitcase design, and what was the fuse rating ?</p></blockquote><p></p>
[QUOTE="marantz123, post: 1064030, member: 16849"] Thanks for the insight. A bit more detail is that the resistors serve to protect the rectifier when hot-switching occurs. An indirectly heated rectifier being switched off and on again while the cathode is still hot enough for emission can cause a rush of current flow which can exceed the guidelines (per plate). Even with the guidelines, the 6x4 was designed with a decent safety margin. The 150 Ohm resistor per plate in this design allows protection up to 200VAC per plate (effectively 400VAC peak-to-peak supply) according to the Sylvania datasheet. This equates to 1.3Amps per plate which is above the guideline, however considering that our plate supply is well below that, its within the 1Amp guideline per plate. The resistors are definitely important in this suitcase design, seeing that there isnt an AC transformer introducing some impedance in the supply to the rectifier. Its still concerning what wattage rating of resistor is to be used here. Out of interest, what is the wattage of the 150 Ohm resistors in the suitcase design, and what was the fuse rating ? [/QUOTE]
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DIY & Tutorials
DIY For Audio
Old Suitcase Turntable Amp Rescue
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