AC In My B-

[Jon1967us]

It's definitely the 35W4 (B-) that is the source of AC ripple. It's a single diode, whereas the 25L6 (B+) is a dual diode and does a better job in smoothing out the DC.

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 25L6.

I'm wondering if I should try putting a 47uF or something between the plate of the 35W4 and the 10Ω?

[Yamamaya42]

Originally Posted by Jon1967us

It's definitely the 35W4 (B-) that is the source of AC ripple. It's a single diode, whereas the 25L6 (B+) is a dual diode and does a better job in smoothing out the DC.

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 25L6.

I'm wondering if I should try putting a 47uF or something between the plate of the 35W4 and the 10Ω?

you could start, by sticking an ammeter in series with the 10 ohm resistor, and using these specs, see if the tube is being overloaded or not, https://frank.pocnet.net/sheets/093/3/35W4.pdf
if it IS being loaded beyond it's spec, you gotta track down what is loading it down, if not, the AC is bleeding in from something else, you should not have to mod anything to get it to work, within reason

[old_coot88]

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.

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.

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.

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.

I'm wondering if I should try putting a 47uF or something between the plate of the 35W4 and the 10Ω?

If you mean bridging the 10 ohm with the cap, NO. That would simply restore ripple that was being dropped across the 10 ohm.