Rivera Thirty Twelve (R30) super Hum!

[Helmholtz]

So you actually have constant beam brightness from left to right even in 5ms/div setting?
If so, your camera is capturing too fast/short.

[Indyryder02]

Old scope. Hard to get it stable enough for a new camera.
In person it’s fine to view.

[Helmholtz]

The repetition rate in the second picture actually looks like 120Hz.
Don't understand why beam brightness isn't constant.

The sharp spikes contain lots of HF, typical for capacitive crosstalk/coupling.

You said +/- 18V heater supplies are clean?

[Indyryder02]

.1 v per div.
really hard to get a good pic of the whole wave. It’s there it just doesn’t show in the pic.

[Indyryder02]

Spectrum analyzer shows a strong peak at 120hz

[Helmholtz]

1st pic without signal. Just hum from the amp.

First scope pic is not interpretable. Something seems to wrong with the scope's time base/horizontal deflection.
Certainly doesn't look like typical heater or ripple hum.

How do you know the hum is 120Hz?

[Indyryder02]

Yes 10x
Starting to think the high gain side is just a noisy bugger by design. Just still seems excessive..

[Indyryder02]

1st pic without signal. Just hum from the amp.
second is with a signal in front. With signal the wave is clean. (Clipping a bit as it’s the high gain channel turned up a bit)

[Helmholtz]

Need to see a periodic signal. Set time base to maybe 5ms/div to see a few cycles.

Are you using a 10x probe?

[Indyryder02]

Starting to think like Enzo originally said.. maybe these models just have this much noise by design. It’s seems to mostly affect the higher gain channel. Which is backwards by most amps as being Ch1. (This whole amps is backwards haha)

Maybe I’m just being too critical as it’s just a bit more hum than I’m used to.

these pics are at the output. Just played both channels with a guitar to get a similar output volume. As the one side is higher gain. So both channels set to a normal playing level of gain and eq and output master volumes. (First pic)

this is rather sensitive settings.
the master output is super loud already at 9 o’clock.
second pic is half way on master. And it has a ton of him then but is rather quite loud by this point too.
I actually owned a Rivera Rake Reverb years ago. But don’t remember how noisy it was anymore.


Of course it’s really hard to get good pics of this old scope.
imagine there’s a series of bumps

[Indyryder02]

[]

Confused.

Does that mean you're not hearing/seeing the hum at the speakers?

I wish. Opposite. I am hearing and seeing the noise at speaker. Otherwise I’d be done! Haha.

think it’s time to go back to the beginning. In too deep and just going in circles.

[Helmholtz]

I started checking from the output back to find it. And started seeing it around V4. preamp tubes to continue trying to find the noise there. I’ll

Confused.

Does that mean you're not hearing/seeing the hum at the speakers?

[Indyryder02]

The tubes were all in during those tests initially. I only pulled tubes after lifting R113, and still hearing the hum. I started checking from the output back to find it. And started seeing it around V4. Felt I was getting in the weeds then so I pulled all but the first preamp tubes to continue trying to find the noise there. I’ll get some scope pics up this morning. The noise on the heaters is constant and looks different.

[Helmholtz]

Hmm, there is a possibility that V2 heater pins and 5 are reversed, so pulling V3 would silence V2A instead of V2B.

Anyway for the tests suggested by Jon Snell you should not pull tubes.
To see if V2B amplifies the hum, you can try to connect a short wire from pin 2 to ground.

Can you post a scope pic of the hum showing scope settings?

[Indyryder02]

Nothing at TP 4. Only the other side of R113 and Pin 1
and that ends with C111 removed. Slight ripple again at R119 but this would be separate with C111 removed and I don’t think it’s related. I keep thinking it’s something with the heaters. The scope is showing what looks like noise on a couple of the heaters.
V1 pin 4 shows the most, pin 5 is less. V2 pin 4 about the same as V1 pin 5.. nothing on V2 pin 5
this is with V3 reinstalled.
Nothing on any other heaters except V5 pin 5. Strange for sure. Not sure if it’s tricking my scope somehow. None of it is adding up for me yet.

tracing further down the heater path. I see the same noise on TP39, one side of D9 and both sides of D7. Stronger on the D7 a TP 39 side.
better step away again. Getting foggy! Haha