I contructed a strobe light but when I power it up, the strobe fires, but there is no power to it.
http://www.aaroncake.net/circuits/strobe2.htm
Some of the modifications I made to the circuit:
I didnt have the 500K pot. at the time so I just put 2 1.8Mohm resistors in place of R2 and R3.
I used a .56 uF cap in place of the .47uF.

I'm thinking the problem lies in my neon bulb. I had to use a really small neon bulb, I had a bigger one but one of the leads broke off. So I figure since the neon is tiny, the voltage is high enough to jump the gap reall easily so no chage builds up in my .56uF cap.
Is this correct? any suggestions?

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Jeff Zimmerman
To the optimist, the glass is half full.
To the pessimist, the glass is half empty.
To the engineer, the glass is twice as big as it needs to be.

 

The size of a neon bulb doesn't make much difference, it still requires a similar voltage to fire - bearing in mind it can vary over a fairly wide range - something like 60V to 90V?.

So I doubt that's your problem?.

I'm not very clear what your actual 'fault' is, am I right in thinking it flashes OK, but the flash isn't very bright?.

The flash power depends on the capacitor that provides the power for it (C2), so perhaps you should try looking round there?.

BTW, what speed is it flashing at?.

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it's probably going at once every 2 or 3 seconds.

Ohhh...the power comes from C2? I thought it was C3 since it was rated for a higher voltage. I couldnt find the correct capacitor to use for that.
that explains it now.

what should the voltage rating be for that cap? because I found another copy of that schematic and it says it should be 315V instead of 350V.

__________________
Jeff Zimmerman
To the optimist, the glass is half full.
To the pessimist, the glass is half empty.
To the engineer, the glass is twice as big as it needs to be.

 

R2 and R3 in cnjunction with C3 determines the Flash Rate.

C2 Determines the Brightness. Too much Capacitance and the Tube will not last too long.

C2 Should be 350 Volts Minimum, Based on 120 Volts AC.
Also a good idea for C1.

Its a Xeon Flash Tube, Not Neon.

Your .56 Cap is Fine.

Take care..........Gary

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I know the xenon tube, I was referring to the neon bulb used to trigger the SCR.

Do C1 and C2 have to be equal values?

Also, where might I find such high voltage capacitors? I have plenty of circuit boards lying around and I wonder if any might have some.

__________________
Jeff Zimmerman
To the optimist, the glass is half full.
To the pessimist, the glass is half empty.
To the engineer, the glass is twice as big as it needs to be.

 

The rectifiers double the 170V peak of the 120VAC mains to about 340VDC. Using a 315V cap is asking for trouble.

The correct polarity of the low voltage winding of the trigger transformer is important, since its high voltage electrode is near the negative end of the flashtube. One polarity adds 340V to the high voltage trigger pulse while the other polarity subtracts.

That odd circuit doesn't have a current-limiting resistor for the neon bulb. It must have a very high-current arc inside instead of a controlled normal glow which could damage it and wastes power from the timing cap. The neon bulb's arc might rob the SCR from enough voltage across its terminals to turn on. Look at the voltage/current curve of a typical neon bulb:

Attached Images

neon_lamp_spec_s.gif (13.3 KB, 558 views)

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Most of these circuits use a NE2, Neon Bulb. But it isn't very Critical, I would think almost Any Neon bulb is fine.
Not Sure what you mean by a Really Small Neon Bulb?

No, C1 and C2 Do not need to be the same Capacitance.

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