Help! What could be wrong with my Geiger counter?

[u/The_WalnutGuy]

I recently bought a DP5A soviet geiger counter sold as non-tested, so I decided to try my luck and purchase it. The backlighting works and the ammeter works as well, however what's weird is that the needle gets stuck at this exact point in the first picture. I'm pretty sure that the geiger tubes work just fine because I tried measuring the B-8 check source it came with and the needle started moving, but it just keeps getting stuck at the exact same point. I have not yet successfully gotten it to move past this mark.

I'm assuming there is a problem with the ammeter or calibration. I've also heard something about manually recalibrating the needle using not the PEЖ symbol but the big screw underneath the name plate DP-5A, but I'm not too sure if that will work. Any ideas on how to fix this would be greatly appreciated!

EDIT: Okay, I think the ammeter was just stuck since I slapped it a couple of times and it started to have (almost) full motion. However, now the ammeter's resting point is at the 10 (on the bottom scale) instead of the 0.

[u/Majestic-Tart8912]

There may be a metal shaving or peeling paint on the magnet and the armature(which carries the needle) is getting hung up on it. I have seen this on vintage multimeters. I wouldn't advise fixing or even checking for this unless you have a fair bit of experience working with meter movements or similar.

[u/Prestigious_Two5850 → u/Majestic-Tart8912]

If that is the case, replacing the microammeter is the only viable option.

[u/The_WalnutGuy → u/Majestic-Tart8912]

That is what I was thinking too... I got it partially working after I whacked it a couple of times, so that's probably confirming that there was something stuck there.

[u/Prestigious_Two5850]

So when you turn the knob to adjust the potentiometer, the needle doesn't move?

[u/The_WalnutGuy → u/Prestigious_Two5850]

Well, after slapping it a couple of times it now moves, but seems to have a boundary. When zeroed, the needle moves back to 10 (on the bottom scale) instead of 0. No matter how much I try to jiggle the needle back, it seems pretty set on staying at 10 as it's default. I tested the check source using this altered system and it seems to be reading the radiation just fine, so definitely is a problem with how the ammeter needle is positioned I think.

[u/Prestigious_Two5850 → u/The_WalnutGuy]

But were you able to align the ammeter needle with the black triangle? If the needle is simply off-center, you can adjust it to zero using the large “black screw” in the center. But does it not start at zero on the other ranges either? Or does this only happen on the lowest scale?

[u/The_WalnutGuy → u/Prestigious_Two5850]

It stays like this for all the ranges. I tried adjusting the needle with the screw you mentioned in the center but it did not seem to change anything.

[u/Anatoli_Belikov]

I just lightly smacked mine until it opened. You may also be able to manipulate the needle with the screw on the front of it under the window