Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: MSVguitar on November 18, 2023, 01:42:47 pm
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I started working on a Premier 120 by replacing the power supply filter caps. Then I decided to replace the paper/wax capacitors. As I was working to replace them I noticed that there is a .02 uF cap to ground on each side of the power transformer primary leads. My first thought was to just remove them. Any reason to replace these?
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... I noticed that there is a .02 uF cap to ground on each side of the power transformer primary leads. My first thought was to just remove them. Any reason to replace these?
Their purpose is to nix noise riding in on the power line. However, you will need a Class Y capacitor (https://www.allaboutcircuits.com/technical-articles/safety-capacitor-class-x-and-class-y-capacitors/) to be sure it will fail safely. These 0.01µF Class Y2 caps (https://www.mouser.com/ProductDetail/KEMET/C791U103MYVDAA7317?qs=IPgv5n7u5QYJdq60A2969Q%3D%3D) are likely a good replacement.
No, you don't have to use them. However, line filtering modules (or power strips) that people buy are partly made of Class X and Class Y caps (perhaps with some common-mode chokes).
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Their purpose is to nix noise riding in on the power line. However, you will need a Class Y capacitor (https://www.allaboutcircuits.com/technical-articles/safety-capacitor-class-x-and-class-y-capacitors/) to be sure it will fail safely. These 0.01µF Class Y2 caps (https://www.mouser.com/ProductDetail/KEMET/C791U103MYVDAA7317?qs=IPgv5n7u5QYJdq60A2969Q%3D%3D) are likely a good replacement.
No, you don't have to use them. However, line filtering modules (or power strips) that people buy are partly made of Class X and Class Y caps (perhaps with some common-mode chokes).
Thank you for the info! I'll replace the caps with your suggestion.