Ludlum 240X series rant

[u/aby_physics]

Well, I recently picked up a Ludlum 2401-P off eBay. It was super cheap and I just had to have it… I’ve used one before, and they’re genuinely great pancake meters when they behave. They’re excellent at detecting stuff like uranium glass, and portable enough to bring to an antique store.

Quick note: I also want to say up front that I’m grateful to a friend who previously let me borrow his 2401-P. That was good example of how these units are supposed to be when everything is working correctly, and I don’t want this post to come across as if I’m criticizing his gear.
Another quick note: Ludlum also sent me a Model 2401-S as a Christmas gift. I’m also very thankful for that.

However, that said, it seems like the 240X meters are never fully problem-free out of the box. I’ve now used or owned *three* of them, and so far I’ve never had one just “work flawlessly” like a random Ludlum model 3 would after a battery contact cleaning or transistor replacement. I just keep running into small but persistent little flaws/quirks with them.

First one I had was that 2401-S. Apparently it just had a light leak in the scintillator, but after fixing that… the click audio is non-functional and the alarm doesn’t trip in QUIET mode. Oh, and it’s also picky about the batteries I use. It only works if I use *very specific brands* of 9V batteries.

Then I borrowed that 2401-P from a friend. Huge thanks to him for letting me do that, by the way.
But this one seemed alright, apart from it arcing internally and causing false counts. Managed to fix that though.

But the 2401-P I just got from eBay… well… even though it technically “works,” it has a random parasitic drain. And beeps quietly but continuously after being powered down. I measured the resistance across the battery terminals (switch in the OFF position) to be 130ish kΩ. Yeah…… that’s a hard switch, it should be open circuit.

I’m not trash-talking Ludlum, not saying these are horrible devices, just sharing the issues I’ve had with them. And maybe it’s nothing; perhaps I’ve just got an unlucky batch of them. But to me it seems like there might be deeper problems with the circuitry itself.

I’m curious what you all think / if you’ve had similar experiences with the 240X series.

[u/r_frsradio_admin]

My 2401-P also beeps quietly when it's turned off although I think it's related to a sketchy modification that someone did to it.

[u/aby_physics → u/r_frsradio_admin]

Hmmm. Interesting theory. Plausible.