A little knowledge is a dangerous thing..... On Sunday, January 18, 2015 at 12:37:23 PM UTC-6, barnbwt wrote: > > The only thing different with the IC2 (driver, vs. nixie-lighting) > present, is that the 5V across the LEDs slowly dies off (I assume because > of an additional trickle ground connection within board that is in front of > the actual LEDs). The 5V and non-amplifying 12V test points do not change > whether IC2 is there or not. I assume IC3 (the high voltage switching chip > that connects the nixie cathodes) has no bearing here, since the high > voltage is not even getting to it (the circuit does the same things, > whether or not it is present). > > The fact that 12V still shows on the far side of the amplifying circuit > tells me that a short is occurring between the input power side and the > output (after replacing it, I do not think the new IRFD220 chip is > nonfunctional, nor the capacitors/resistors accompanying it). This is > good, since it appears there are very few 12V elements in the circuit, the > rest being either 5V or high voltage. Narrows down the possibilities. > According to the diagram, the UF4004 diode (D5) is the primary element > separating the 220V output of the MOSFET from the 12V input (I am > admittedly a bit confused by the circuit diagram representation, but I am > guessing high voltage pulses are deflected by the inductor L1 and then flow > across the diode D5 where they the remain). I suppose I'll try replacing > D5 next, with another +400V 1amp unit (so long as its activation voltage is > well below 12V it should still open, right?). The diode does show one-way > metering, and a test value of 350, but I just don't see what else could be > connecting the 12V and MOSFET outputs. What would cause the MOSFET to > generate a gain of 1.0? > > Given the amount of damage the board is sustaining from all my picking at > it, this diode swap is probably the last thing worth trying before starting > over (frustrating, since I successfully hooked up a nearly-identical kit a > neighbor needed help with, with no trouble whatsoever) > > TCB > > On Sunday, January 18, 2015 at 5:11:32 AM UTC-6, Ryan wrote: > >> HV sense resistors are all good? Have you tried it out with the driver IC >> removed? If that's all good and the FET is not shorted, might be an issue >> with the microcontroller. >> >> On Sun, Jan 18, 2015 at 3:12 AM, barnbwt <[email protected]> wrote: >> >>> Alrighty, >>> I got the C3 and C4 HV circuit capacitors switched out (the closest >>> quivalent for the C4 were a considerably higher voltage rating, 35V vs >>> 16V. The C3 I found was identical, but a much larger metal-film version >>> rather than electrolytic). I also re-flowed all the solder connections in >>> the HV circuit components left in place. I don't *think* I'm changing >>> anything, but the following appears different: >>> >>> -The die-off of the circuit seems to happen a bit faster with the new >>> capacitors (it reverted when I replaced the new caps with the >>> better-fitting originals) >>> -The die-off of the LEDs does not occur when the IC2 board is not >>> installed (circuit just stays lit, but still not generating high voltage) >>> >>> I checked all the diodes, and they are still blocking current the way >>> they are supposed to (can't measure the figures, though). I also checked >>> each soldered connection to the next component in the chain, and nothing in >>> the HV circuit is open circuit (bad solder joint/etc.). Looking at the >>> diagram, I don't think I can isolate the HV circuit from the rest without >>> removing a bunch of components for the LEDs and nixies, so I'm officially >>> at a loss for the next step in troubleshooting. Even if I had access to a >>> scope I'm certain I don't know how to use it. I'd obviously buy another >>> 70$ kit before a 300$ scope, at least until that one cooks, too. >>> >>> I *think* the fault lies outside the HV circuit (but connected to it, >>> thus draining its voltage output to 12V), or I've managed to cook the >>> IRFD220 again (which would be surprising, since I took even greater care to >>> solder it without overheating this time, and the first go-around actually >>> work until the short), or the IC2 chip is nuked and cannot activate (but >>> I'm more inclined to think the lack of a high voltage at its sensing input >>> is the cause for that) >>> >>> TCB >>> >>> -- >>> You received this message because you are subscribed to the Google >>> Groups "neonixie-l" group. >>> To unsubscribe from this group and stop receiving emails from it, send >>> an email to [email protected]. >>> To post to this group, send email to [email protected]. >>> To view this discussion on the web, visit >>> https://groups.google.com/d/msgid/neonixie-l/b97e0a4e-c6ee-42d8-90b3-f14a7f0cc6c4%40googlegroups.com >>> >>> <https://groups.google.com/d/msgid/neonixie-l/b97e0a4e-c6ee-42d8-90b3-f14a7f0cc6c4%40googlegroups.com?utm_medium=email&utm_source=footer> >>> . >>> >>> For more options, visit https://groups.google.com/d/optout. >>> >> >>
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