Replaced neons in Fluke 845AR

[EE4all]

I obtained a broken Fluke 845AR, with wild meter swings. Upon opening and inspecting the neon chopper bulbs, they were a little dim, and blackened.

I replaced them with some NE2U A3C tubes that were readily available locally. This alone has brought the meter back to life and now I can zero it, with around +- 50 nanovolt noise swings on the most sensistive 1 microvolt range. Is this about normal?   

Some further notes:
I pulled the old tubes out and made a comparison of their behavior compared to the old ones. With a 30K resistor in series, and the room darkened, the new ones ignite around 12 volts lower (104v vs 116v) than the old ones and of course have clear glass. I also noted that originals lit up the entire electrode inside, whereas the new ones light only in the center. Therefore, I measured a small amount of extra height was needed to align this Illumination with the center of the glass tubes. Pictures of old and new attached.

[EE4all]

Another note, it is good to check the tubes before installing them. I bought a box of 10, and the first one that I tested would ignite in one spot and then flicker down to another for the solid burn. I did not use that one. The next 2 out of the box stayed lit in the same spot that they ignited from, and I used those.

[EE4all]

I noticed some older threads digging into the noise measurements and such. I will have a read, do some of my own tests  and report back anything interesting.

[enut11]

There are also threads on the Forum somewhere replacing the neons with LEDs

[EE4all]

I found 3 capacitors in need of replacement at half their rated capacitance, and another few borderline, so today I just went ahead and ordered a full replacement set from Mouser. I was able to find good replacements in stock with high temperature, voltage, and capacitance ratings a bit above their specification, as the originals were all rated at the typical -10 to +50% specification as a lot of axial capacitors of the era were.

I will come back to checking the noise and performance after the full recap.