> Not sure what is going on but I checked the circuit and I am getting > 613VDC with the 180K Resistor (R3) in the schematic. I increased the > resistance to 270K and I still get 613VDC. Not sure why this is. > Anyone have a thought on why I'm getting 613VDC? > > John
On what side, do you get the 613V. If its the side away from the anode, then it may be okay. And it won't change with resistor. What's the voltage across the dekatron (anode pin to cathode pin - any cathode) ? What's the voltage across the anode resistor ? Divide that number by your resistor value (used) to get the current. Dieter got a little carried away with the multiplier ladder. If you use capacitors that are too small, the ripple will be outrageous, so the average voltage won't go up to the calculated value. In the '120 World' you really don't need more than 1.5x multiplication. REMEMBER 120V is the RMS (Root Mean Squared - or DC equivalent work) value. The sine wave really has a 165V peak value, and ~330Vpp (peak-to-peak) value. Look at the following drawing: http://snipurl.com/1asxej http://cid-f9db37b8211ce831.office.live.com/self.aspx/Snippets/Multiplier%5E_basics.gif Refer to image 'D'. If you put 120V (110V, 115V, 117VAC) RMS into that circuit, you'll get ~500VDC out, unloaded. The light load most dekatrons put on this circuit (assuming an appropriate anode resistor), should not induce too much ripple, so the voltage measured won't sage too much. On circuit 'D', the lowest located rectifier, and capacitor form a simple half wave rectifier & filter, which will output +165VDC, unloaded. The left most capacitor's bottom end is riding on the input AC signal. It's top end is tied to the anode of the rectifier, that's tapped off the +165V. Since this voltage is dynamic (moving), the top end will also try to stay in step with the bottom end (this is what the coupling caps in your stereo does). But its attached to the +165V (thru a rectifier). The bottom of the cap will make a 330V swing from -165V to +165V. When the swing is all the way down at -165V, the top is forced to +165V by current flowing thru the rectifier. This will charge that cap to 330V from top to bottom. As the sine wave goes back up, the top will still stay in step, which will make go over the 165V, so that diagonal rectifer (now being reversed biased) is switched OFF. When the input sinewave hits +165V, the top of the cap will be at nearly 500V (495 or there abouts). In the meantime, it would be charging the upper right cap. With no load, this circuit will present a DC voltage of close to 500V. In the 220V (220, 230, 240) world, you can get away with circuit 'C', which will give you 660VDC unloaded. Don't worry too much about the voltage. Dekatrons, like nixies (and LEDs) are current devices. Its the current flowing thru them that's important. And that's controlled by the anode resistor. You can use a 'test' resistor for temporary measurements. You need to measure (1) the actual supply voltage, and (2) the 'tube drop' voltage from anode to a cathode. Once you have those two, then you can determine the 'final' anode resistor value you want, from the specs given for that tube. (ie the anode or cathode current). The resistor will simply be supply voltage minus tube drop to give you the anode resistor voltage. Divide that voltage (anode voltage) by the desired current, to get the actual value, or close to it. Pick a real value made that's less than 40% away from that calculated ideal. In the Philips datasheet for the Z504S dekatron, the maximum allowed supply voltage is 1000V. That's why you see values from 400V to over 600V commonly used. It really ain't that critical, as long as you adjust your anode resistor, accordingly. -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. To post to this group, send an email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/neonixie-l?hl=en-GB.
