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Originally Posted by Jon1967us
It's definitely the 35W4 (B-) that is the source of AC ripple. It's a single diode, whereas the 25Z6 (B+) is a dual diode and does a better job in smoothing out the DC.
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The 'Z6 is strapped as a simple half-wave diode like the 35W4, making it irrelevent that it's dual. The job of smoothing is done 'downstream' of the tube.
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I'm measuring 2.4VAC at the 35W4's plate and it gets dropped to 1.6v at the junction of the 10Ω and 270Ω - only .2VAC is leaving the smoothed DC coming from the 25Z6.
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From the voltages you cite, it's doubtful that supply ripple is causing the large bending in the raster. But if you still suspect ripple, there's an easy test for it: While observing the raster (use a mirror if necessary). Get another 47uf electrolytic and momentarily bridge and un-bridge each of the two filter caps (observing proper polarity of course). If there is little or no change in the bending, it's not a ripple problem.
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I'm wondering if I should try putting a 47uF or something between the plate of the 35W4 and the 10Ω?
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If you mean bridging the 10 ohm with the cap, NO. That would simply restore ripple that was being dropped across the 10 ohm.