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DIY For Audio
Restoration of Philips B6X63A valve radio from 1956
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<blockquote data-quote="El Sid" data-source="post: 890164" data-attributes="member: 18550"><p>So I swapped the output transformer and certainly the volume is better, but there is still distortion as you can see on the trace below. B9 is the treble valve in question. The input at the grid is the lower trace so that's fine. It gets worse with amplitude, because at very low volumes it looks more sinusoidal. Is the EL84 being overdriven? I measured the voltage at the cathode and it's at 15.V, which given the 220 ohm value of the cathode resistor R54 implies a cathode current of 69mA, which seems too high. Is that resistor maybe poked?</p><p></p><p>Anyway, before taking the brute force route of changing all the components I thought I'd put it to the gurus and see if anyone has a theory. Thanks!</p><p></p><p></p><p><img src="https://i.imgur.com/S4OJLyO.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" /></p><p></p><p><img src="https://i.imgur.com/R5gzmlj.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" /></p></blockquote><p></p>
[QUOTE="El Sid, post: 890164, member: 18550"] So I swapped the output transformer and certainly the volume is better, but there is still distortion as you can see on the trace below. B9 is the treble valve in question. The input at the grid is the lower trace so that's fine. It gets worse with amplitude, because at very low volumes it looks more sinusoidal. Is the EL84 being overdriven? I measured the voltage at the cathode and it's at 15.V, which given the 220 ohm value of the cathode resistor R54 implies a cathode current of 69mA, which seems too high. Is that resistor maybe poked? Anyway, before taking the brute force route of changing all the components I thought I'd put it to the gurus and see if anyone has a theory. Thanks! [IMG]https://i.imgur.com/S4OJLyO.jpg[/IMG] [IMG]https://i.imgur.com/R5gzmlj.jpg[/IMG] [/QUOTE]
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DIY & Tutorials
DIY For Audio
Restoration of Philips B6X63A valve radio from 1956
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