Kit stopped working, low voltage

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nbrand
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Joined: Thu Dec 15, 2011 11:43 am

Kit stopped working, low voltage

Post by nbrand »

Hello,

My unit recently stopped working, and it is probably a solder joint. I can measure about 36 volts across the tube, which is about 1/10th
of what I would expect. Should I focus on the IC chip, or does anyone have an idea of what pins to inspect?

Correction, after replacing the batteries and testing the connections, I now get about 0.3-0.45 volts. About 1/1000 of what I need.
It is clearly a solder joint issue or perhaps the HV chip. I will do some more visual inspection, and then do some re-soldering. Things look clean, though.

I will check the schematic and use a multimeter, and post what I find. BTW, the correct voltage is showing across the J6 pulse points.


Thanks,

Nick
Last edited by nbrand on Thu Dec 15, 2011 1:21 pm, edited 1 time in total.
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mightyohm
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Re: Kit stopped working, low voltage

Post by mightyohm »

Hi Nick,

What kind of meter are you using to measure the voltage, and are you using a 1 GigaOhm in series with it as described in the PDF instructions?

Do you hear a faint whine from the speaker when you turn the kit on? Are the batteries fresh and tested at 1.5V each?
nbrand
Posts: 3
Joined: Thu Dec 15, 2011 11:43 am

Re: Kit stopped working, low voltage

Post by nbrand »

Hi Jeff,

Happy holidays and thanks for the reply.
I had posted a reply, but I was not logged in so it was lost. This is an abbreviated version... :-)

Once I got the schematics, I started to understand the design a bit. It looks like a 555 timer is triggering voltage pulses
that are being multiplied by inductor L1. As I am getting zero voltage across TP2, and no sound upon start-up,
I decided to look there.

I checked the Vcc and GND pins on the 555 timer. No voltage reading. After inspecting the board again,
I replaced the chip with a spare I had, and voila - 3 volts! Unfortunately, I do not have the low-power 555 [TLC555CP] as a spare,
so the device is still not working. However, it does prove that the 555 was blown. I may have a short somewhere.
I will order some replacement chips and then see if I can investigate the short before I blow it up again.

The 555/inductor is a clever design, although probably not as reliable as a Cockcroft–Walton (CW) generator, or multiplier
which are typically used in a geiger counter. I am not sure what the mini processor is doing, as I do not know how complex
it is to trigger a LED/buzzer upon signal. If so, it is overkill. Of course, there may be some more complex logic processing going on.

I will post again after I get some replacement chips, in about a week.

Thanks again for all the assistance!

Nick

PS. I agree that a v2 should have pads for all points. When it worked, it did chew through batteries quickly, so perhaps a larger
capacity, or external supply.
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mightyohm
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Re: Kit stopped working, low voltage

Post by mightyohm »

nbrand wrote:Hi Jeff,

PS. I agree that a v2 should have pads for all points. When it worked, it did chew through batteries quickly, so perhaps a larger
capacity, or external supply.
Can you explain what you mean by "pads for all points"?
nbrand
Posts: 3
Joined: Thu Dec 15, 2011 11:43 am

Re: Kit stopped working, low voltage

Post by nbrand »

Jeff,

My mistake. It just seems that some of the pads are especially small, which did not allow
for a solid solder connection. The batteries points in particular, but there are other critical points
where a larger pad would of made things easier. The layout is very good, so there seems to be ample
space for more contact area.

Nick
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Re: Kit stopped working, low voltage

Post by mightyohm »

The next revision of the design will address this with larger pads for many components.

Thank you for the feedback!
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