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Audio and Video Talk
Valves / Vacuum Tubes
SE or PP el84?
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<blockquote data-quote="Family_Dog" data-source="post: 774939" data-attributes="member: 82"><p>Correct on both counts, El Sid <img src="data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7" class="smilie smilie--sprite smilie--sprite1" alt=":)" title="Smile :)" loading="lazy" data-shortname=":)" /> Many old caps tend to degrade and build up an internal resistance, thereby leaking DC. It doesn't take much DC to fully bias the EL84 into permanent conduction mode. This, apart from drastically shortening the life of the output valve, could lead to the output transformer burning out.</p><p></p><p>The filter caps dry out and lose their effectiveness thus allowing 50 or 100 Hz DC ripple to appear on the HT voltage, causing audible hum through the speakers.</p><p></p><p></p><p>-F_D</p></blockquote><p></p>
[QUOTE="Family_Dog, post: 774939, member: 82"] Correct on both counts, El Sid :) Many old caps tend to degrade and build up an internal resistance, thereby leaking DC. It doesn't take much DC to fully bias the EL84 into permanent conduction mode. This, apart from drastically shortening the life of the output valve, could lead to the output transformer burning out. The filter caps dry out and lose their effectiveness thus allowing 50 or 100 Hz DC ripple to appear on the HT voltage, causing audible hum through the speakers. -F_D [/QUOTE]
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Audio and Video Talk
Valves / Vacuum Tubes
SE or PP el84?
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