Rivera Thirty Twelve (R30) super Hum!

[Enzo]

IC2 is a negative regulator, it has a different pinout from the positive ones. If IC2 were dead, you wouldn't have half the heaters working

[Indyryder02]

yes, those are the outputs.
the input is Pic 1 for both IC 1 and 3
and this is a pic of the input of IC2. Which has no output. (I suspect it might be fried possibly. But I don’t think it would be causing the noise. Just another issue all it’s own. I might have hit it with the probe doing all this testing around it.

[Indyryder02]

IC2 is giving different basic diode checks then 1 and 3. Just where it’s at in circuit maybe? Only without output it seems.
may not be the cause of noise. Maybe just failed?

[Enzo]

If that last waveform is the output of a regulator, look at the input to that regulator. Is the raw DC unfiltered?

[Indyryder02]

IC3 has the same input and output noise as IC1

[Indyryder02]

Yeah. It was a whim of hope haha.
Replaced it with no change. Not surprised.

[g1]

Not sure about the influence of C15. The wiring of IC3 looks wrong.

Agree, the IC3 regulator wiring is messed up. It looks like it is the supply line for the LDR's.

[Helmholtz]

So this is at TP39 (largest amount of noise it seems) as well as the input of IC1 (labeled “input” at IC, this would be on the left in the schematic? Output on the right?). And the second pic is of the output of IC1
IC2 only shows noise at input. (3rd pic) the time division isn’t ideal for seeing the noise. About one off unfortunately. But this is the only position it shows the full beam.

Only the noise on the filament regulator outputs matters for heater hum.
So the output of IC1 looks suspect.

Not sure about the influence of C15. The wiring of IC3 looks wrong.

[Indyryder02]

I just realized.. C15 didn’t get replaced! It’s sort of hidden up next to the controls opposite the board of C13 and 14.
surely it can’t be this little fellas fault!?

[Helmholtz]

Looks as if the camera only captures for maybe 7 ms. The faint rest of the trace is probably phosphor afterglow from the previous trace.

[Indyryder02]

Ok. Got it better with a time lapse setting.

[g1]

Can you turn down the timebase one more notch so we can see a complete cycle?

edit: nevermind, didn't see the latest post. Sometimes if you play with the inner 'calibration' knob, you can get in between settings.

[Indyryder02]

So this is at TP39 (largest amount of noise it seems) as well as the input of IC1 (labeled “input” at IC, this would be on the left in the schematic? Output on the right?). And the second pic is of the output of IC1
IC2 only shows noise at input. (3rd pic) the time division isn’t ideal for seeing the noise. About one off unfortunately. But this is the only position it shows the full beam.

[Indyryder02]

No, I said it definitely looks like noise on the heaters. I see it on the diodes in line as well. Which brings us back to the heater lines filtering as previously mentioned. (Or could it be coming from one of the IC’s? ) C11 and 12 are new. Yesterday I was looking at this and traced the noise back to TP39 to C11
it’s on both sides of D7 to varying degrees (waveforms look different, attached) and only the anode side of D9.

[Enzo]

I suspect we are seeing one trace across and then most of another sweep, so the portion that includes both sweeps is brighter than the portion with only a single sweep. The camera interval is not in sync with the scope image.