GQ Electronics Technical Support Forum Active Users: / Visits Today:
Highest Active Users:
GQ Electronics Technical Support Forum
Home | Profile | Register | Active Topics | Members | Search | FAQ
Username:
 Password:
Save Password
Forgot your Password?

 All Forums
 GQ Electronics Forums
 2.GQ Geiger Muller Counter
 GMC-500+ Tube 1 (M4011) shows 0 CPM – need help

Note: You must be registered in order to post a reply.
To register, click here. Registration is FREE!

Screensize:
UserName:
Password:
Format Mode:
Format: BoldItalicizedUnderlineStrikethrough Align LeftCenteredAlign Right Horizontal Rule Insert HyperlinkInsert EmailInsert Image Insert CodeInsert QuoteInsert List Spell Checker
   
Message:

* HTML is OFF
* Forum Code is ON
Smilies
Smile [:)] Big Smile [:D] Cool [8D] Blush [:I]
Tongue [:P] Evil [):] Wink [;)] Clown [:o)]
Black Eye [B)] Eight Ball [8] Frown [:(] Shy [8)]
Shocked [:0] Angry [:(!] Dead [xx(] Sleepy [|)]
Kisses [:X] Approve [^] Disapprove [V] Question [?]

   Insert an Image File
 Check here to include your profile signature.
    

T O P I C    R E V I E W
bialex Posted - 04/03/2026 : 12:42:41
Hi all,

I’m having an issue with my GMC-500+.

Tube 1 (M4011, marked 2022) constantly shows 0 CPM, while Tube 2 still detects background radiation (~1–2 CPM), so the device is not completely dead.

What I’ve tested so far:

Tube 1 voltage set to ~42% (~417V), later reset to default (~52%): still 0 CPM
Performed factory reset: no change
When I manually short/touch the Tube 1 input terminal, the green LED flashes and CPM1 increases, so the counting electronics seem to work

So it looks like:
counting circuit works
Tube 2 works (low sensitivity as expected)
but Tube 1 produces no pulses at all

My question:
Is this more likely a dead M4011 tube, or could it still be a HV supply issue on Tube 1 channel?

GQ Electronics Technical Support Forum © Copyright since 2011 Go To Top Of Page
Generated in 0.04 sec. Snitz's Forums 2000