Mine: HV low, then Stopped working- Help Thanks!

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PiledHigherDeeper
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Joined: Sun Mar 30, 2014 9:10 pm

Mine: HV low, then Stopped working- Help Thanks!

Post by PiledHigherDeeper »

After getting this kit some time ago, I got some post surgery time to put it together... My kit seemed to work great, if not a little anemic on detection of Uranitite's emissions.... So I checked TP2 to Ground using my Fluke T5-600... (not the ideal VMM per https://www1.elfa.se/data1/wwwroot/asse ... nual_e.pdf, tomorrow I may have to go get the good DMM out of my shop across town). It was showing 35vdc-135vdc with VR1, so I cross checked this on another older (probably less impedance) multimeter I had here at home, for grins.... and things seemed to show nothing on the HV side, just 3vdc on TP2...

I went through all your online troubleshooting (per viewtopic.php?f=15&t=3339), and I think I got it all right, even if a few solder points have a little singed varnish with the resolders and added solder.... This did not help. The diodes and transistors seem right. I have not tested the 555 any more than looking for ANY HV on leads, but only see 3VDC max everywhere (approximately using this: http://dl.dropboxusercontent.com/u/3572 ... ematic.png). I shorted the GM tube with and without it in, no chirps. Never got chirps on turn-on either.

So I began surfing all the low voltage posts here, and this one worried me: viewtopic.php?f=15&t=3496 as I think I tested TP1 to ground - I DID get a chirp, but maybe I killed the U2 memory doing that? Yikes!- maybe a warning about that potential is worth going in the Troubleshooting section?) For a spell I thought the GM tube was the culprit, but I am not so sure now. I am using a placeholder low-end SI3BG Tube (one of these: http://www.ebay.com/itm/TESTED-SI-3-BG- ... 48506a0992) to get the PCB going, and if all is well Been looking to put an LND 7317 or SBT-11A pancake tube on this one, but I want to get the board right on a cheap tube first... (I'll post separately about the pancake tube future hookup, see if anyone has etc...).

Note, I DID put in the super-bright (blue) jumbo LED with a zero ohm jumper for R11 - but I don't think that would have been the culprit, right? So I have not messed with undoing that yet...

So any thoughts on what to troubleshoot next? Once I get my better meter, maybe try this testing, at forum thread t=10#p5489 ?

I used to build stuff as a Ham couple decades ago, but been awhile, pretty rusy!... any help greatly appreciated!
Paul, Flagstaff AZ, NT3L
PiledHigherDeeper
Posts: 7
Joined: Sun Mar 30, 2014 9:10 pm

Re: Mine: HV low, then Stopped working- Help Thanks!

Post by PiledHigherDeeper »

I got ahold of my Fluke 45 (http://www.testequity.com/documents/pdf/fluke45.pdf a not terribly cheap VMM but seems still 1MOhm impedance?) and tested the voltages as described in http://www.mightyohm.com/forum/viewtopi ... t=10#p5489

I get these values with ground to Pin3 of J6:

Batt Pack+ 3.208V, - 0.02mV
J6 pins 1 & 3 3.209V
TP1 3.206V (I occasionally get an LED flash if I wait to touch this 5+ second intervals)
TP2 only 2.997V

U1 Pin1 0.04mV
U1 Pin2 0.06mV
U1 Pin3 0.08mV
U1 Pin4 237.95 mV
U1 Pin5 2.13V
U1 Pin6 0.4mV
U1 Pin7 0.05mV
U1 Pin8 3.211V

+ End of GM-Tube Clip (tube in) 2.018V
- End of GM-Tube clip (tube in) 0.04mV

I pulled the 555 and checked it and its pins - no physical issues.... I checked the Transistors were all in the correct spots again
Some pics of the PCB:
http://s1093.photobucket.com/user/PaulZ ... sort=3&o=1
and
http://s1093.photobucket.com/user/PaulZ ... sort=3&o=0

Any recommendations on "what next", are greatly appreciated!
Paul Flagstaff AZ NT3L
PiledHigherDeeper
Posts: 7
Joined: Sun Mar 30, 2014 9:10 pm

Re: Mine: HV low, then Stopped working- Help Thanks!

Post by PiledHigherDeeper »

Hmm - while waiting for feedback - I went to the Shack and got some components I could find (transistors Q2, Q3, and the 555)...

I found the problem I think....

I replaced U1 and nothing changed. So I desoldered Q3 out first, and replaced it - and voila - the board now seems to work.... (I left Q2 alone; and Radio Shack did not have the Q1 transistor).

So on my Fluke 45 HV now can max out at 435 VDC, and I start getting chirps at 315 VDC, so I set it to about 355 VDC.

The PCB is happily chirping along, though it did NOT seem terribly more responsive to a Uranitite sample -- but I blame THAT on the "econo-tube" I am testing the PCB with at the moment (a little SI-3BG). When the pancake arrives, hopefully (1) I will have enough voltage, and (2) I will see real sensitivity...
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Re: Mine: HV low, then Stopped working- Help Thanks!

Post by mightyohm »

Glad you got it working!
The SI-3BG is extremely insensitive - it takes an extremely powerful source to get any activity - generally more powerful than is safe to handle.
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