Thanks! Good analysis. I got the GMC500, and glad to see your take on these.(I've had a Heath kit for 20yrs+, but never got it soldered together!)

@danmiller2940

3 жыл бұрын

I have a Heathkit ham radio that was assembled long ago. It is a beautiful machine. I can't imagine having the skill and patience to assemble such a thing.

Thanks for tearing yours down. I don't have to do mine now! :) On the IC with no markings, I've found it somewhat common for makers of proprietary devices to remove those. Sometimes it's done to prevent identification of the device's purpose (i.e. bootleg cable/satellite theft devices), or to prevent reverse engineering of the design. I've actually seen the chip's numbers physically ground off with sandpaper or dremel.

Thank you very much for this analysis, it helped me to know if it worth buying it.

@benjamin morrow. I Cant reply directly to your comment due to your G+ permissions. But i doubt it was a rooster, most likely the screaming kids next door!

Great video ! Also have the 300E Plus G-M Counter from Seattle. The Battery is a Li-Ion Model 14500 3.7 V Battery and rechargeable. Also the G-M Tube is glass. Thank you for the video ! tjl

I have ordered this Geiger counter. It should arrive tomorrow. Looks like I have some studying to do.

Really helpful. I have the same model and my only criticism of it was that while reasonably immune to regular indoor lighting. if you have it in your back pocket on a bright sunny day, it will go into alarm mode with absurdly high readings. I painted the inside of the case with matt black paint which helped considerably but then tried coating the tube with black paint which alas made the tube very insensitive to anything. On the upside as I only used a black emulsion, it was not hard to remove and restore sensitivity. Unsure why applying paint to the glass should affect it, I am wondering in hindsight if possibly the paint was very slightly conductive and because it went right up to the cap, it might have been dragging down the tube voltage. I noticed on your video (thank you by the way), that near what I also reckon is the HT unit, there is a small potentiometer. For some reason I didn't spot it on mine but I am going to disassemble again and try to see if this is part of the HT circuitry in which case if I re-coat the tube (avoiding the very end where it touches the metal caps) and the sensitivity falls along with the ET, I can hopefully adjust it with the trimmer. Button sensitivity is weird on mine too. Curiously on my unit, instead of a PP3, there is an AA sized 800mA rechargeable lithium cell which will recharge when the mini USB is connected to a 5v supply (typical USB charging type system). If you remove the glued in AA holder and also remove the plastic "fin" on the case and foam pad on the underside of the removable battery compartment, it is possible to install (slightly diagonally and you might need to loose the top right mounting post) a 2500mAh cell instead. This lasts over 4 times longer (as opposed to perhaps the more expected 3 times) than the original and is good if you want to take it on lengthy field trip with perhaps limited access to convenient charging. Overall a good unit but frustrating that "as-is" it becomes VERY unstable if used outside in bright sunlight. (Subdued sunlight seems to be fine as does most indoor lighting). With your home made unit, did you ever try one of the SBM-19 tubes? They are apparently incredibly sensitive to background / distant sources which might make locating interesting items at flea markets etc more easy. About to order one and see what I can find but would be VERY interested to hear if you had ever tried one. All the best - and thanks for a really useful review. Mark

in large font mode you need to hold the buttons down for it to respond

what are you using as a sample? id really like to test my 500plus but i have nothing in the house or outside i can get a response from.

Haha was that a rooster I heard in the background?

Hei dexterlabs2013, nice video...could you tell me what's the name of the mightyohm's tube?

@DextersTechLab

6 жыл бұрын

it's just a regular SBM-20.

wheres dl#40?

What is the other geiger counter you have?

@DextersTechLab

4 жыл бұрын

I have a few, a Ludlum Model 3, a FAG FHT-111M, a MightyOhm Geiger Counter and an old a old Mini Instruments environment monitor. There should be videos of all of them somewhere on the channel.

Have a CD V-700 and a CD V-742 and hope to visit the Trinity Site in the Spring of 2016. More info at the dot mil website ! Saw a Fiesta Plate for about $27.00 USD on ebay from NM (New Mexico the extraterrestrial friendly state) Thank you for the video ! tjl

More in natur please!

was just wondering why this unit does not detect alpha rad

@DextersTechLab

9 жыл бұрын

Jordi Sosa to detect Alpha particles you need a GM tube with a Mica window which allows the particles to enter the tube and be detected. Normal GM tubes made from metal or glass will block Alpha particles.

The later ones just a couple years after this was uploaded stopped coming in as nice of a box as this. No little bag for it,the USB cable not as nice looking, and no 12v socket adapter.

tnx

Mine failed soon after purchase. TheGMC 500 is disappointing in the build quality.

I've had a fair bit of experience with the GMC range of detectors from GQ, having been able to take them into work with me (nuclear fuel research) and give them a good test! Despite having a fair few issues with my first (a GMC-300E) and my second (a GMC-320 plus), I still use them quite often for 'playing around' with materials at home etc. Have you had any hardware/software issues with yours at all Mark? My 300E started switching itself off randomly (when not in power saving mode), and the battery indicator reads 30% at all times, and the screen mode will change randomly on its own in higher radiation fields! And we're not talking danger levels, my ww1 radium watch upsets it sufficiently! As do even slightly 'spicy' ore samples. And my first GMC-320 plus started draining lithium cells down to 0v after just 12-15 hours with a pretty high quiescent current, rendering it pretty useless. But, the final 320 plus I purchased has been a gem! I mounted the SBM-20 tube in place of the original tube (as you did on your 300E), but also mounted the stock glass tube next to it, in parallel, giving very high overall sensitivity (set to 325 cpm/uSv/hr). So background is around 35cpm with the double tube arrangement, a worth while mod! Regards, Jason.

@DextersTechLab

6 жыл бұрын

No issues to report on mine. Nice idea with the double tube!

@tensevo

3 жыл бұрын

I have the GMC-300E model and I am currently unable to register any CPM on my device. Everything seems to be working on the device, battery is fully charged, menu buttons and display all work fine, just no clicky and no CPM. It reads 0CPM after days. I've had the back off and the tube is intact. I was reading on the forum they changed tube from M4011 to J305 in order to make it less sensitive to visible light. I have the J305 tube in mine. Any ideas much appreciated.

@longden57

3 жыл бұрын

@@tensevo What I would do is test the tube has the required voltage - you're looking for something higher than 350V (ideally around 380V). To do this you'll need a multimeter with at least a 10 megaohm or greater input impedance. I actuall use a 1 gigaohm resistor in series which doesn't impact the circuit too much. With a 1 gigaohm resistor in circuit my multimeter shows 3.7V on my 300E (this correlates to around 370-380V when using the 1 gigaohm resistor). If you have the required voltage then the tube is likley at fault. Hope that helps. Jason

@tensevo

3 жыл бұрын

@@longden57 Excellent, will try that.

Nice... reads the manual first, next channel review.

is that fingernail fungus, or do you bite your nails?

@DextersTechLab

9 жыл бұрын

To SERVE Man Nice of you to ask, it is Psoriasis, go wiki if you dont know what it is.

@2right4words

9 жыл бұрын

DextersLab2013 usually that has arthritis associated with it

The quality of the plastic build is appalling. Can't they have more pride in their product?

Windblows is crap. There's no Linux stuff for this. There is a Python script but I haven't had luck with it.