Slight background crackle--can the source be a rectifier tube?

So my VTA120 has worked flawlessly for three years until yesterday. While listening I detected a background 'crackle' in both channels.

My first inclination was to pull the driver tubes and shuffle them around to see if the noise moved or even disappeared. For some insane reason I also pulled the rectifier tube at the same time. I then realized that this would complicate matters so plugged it back in.

However in the process of plugging it back in, I somehow did not align it correctly (even though there is a tab on the tube base) and with the pins in the wrong holes turned the unit on.

Rectifier tube did not light, even though the driver board tubes did along with the power tubes. I shut the until off, realized my mistake and re-inserted the GZ34 properly.

Turned on the unit, but the GZ34 didn't light.

Shut the unit down, inserted a fresh GZ34 and fired the unit up.

Everything sounds fine now. Not sure if pulling/re-inserting the driver tubes cleared the crackle of if the original rectifier tube was going bad in the first place.

Thoughts?

As the sound comes from both channels it should have a common cause. Powersupply is a possibility.
Also bad contact in the mains supply ( fuse not ok, bad solders, bad power switch could cause this).
Another common source is the bin electrolytic cap, and as you mentioned the rectifier tube, although
a failing rectifier tends to self-destruct fast.

Thanks. Really wish I hadn't mucked with the GZ34 but that is water under the bridge. I don't have many hours on the unit taken as a whole, so was surprised when the noise started. Running it all day today to see if things are truly cleared up.

jsl1234 wrote:Thanks. Really wish I hadn't mucked with the GZ34 but that is water under the bridge. I don't have many hours on the unit taken as a whole, so was surprised when the noise started. Running it all day today to see if things are truly cleared up.

So how's the amp?

Sorry for the late reply, on a road trip. Yes, it seems removing and reinserting the driver tubes cleared things up. As I mentioned I also replaced the rectifier tube so I’ll never be 100% certain which one was the root cause, but my money is on the driver tubes.

Is it advisable to use some type of dielectric grease on the tube pins to stop any type of corrosion?