I think you'll find that replacing the 220uF cap with a 0.47uF cap will solve your problem. Although I realize it may sound strange.... I think what happens is that when the HV switch opens, C1 cannot supply the current to charge this huge capacitor and the current will flow in negative direction through the 7805 which causes it to heat up. You may want to put a series diode in forward direction to the input of the 7805, that will also solve the problem I think.
Michel On Nov 24, 6:08 am, secretsather <[email protected]> wrote: > @nixiebunny - I will give this a shot. I wonder if this could be the cause? > > @Michel - Yes, it's drawing 500mA total current (both lv and hv), so I'll > isolate the LV and check it with a meter to see how much current it is > drawing next time I get a chance (hard to do things around the holidays) > Also, you're right about the capacitor, I looked at thge schematic I used > for the 555 nixie driver, and noticed it's only supposed to be a .47uF cap. > I'm using a 220uF, and what was I thinking? This will be the first thing I > try (is replace the cap). I'm using a lab power supply if that makes a > difference. > > @mikegregg - I don't have any resistors leading to the base of the > transistors. The datasheet for the transistor array I'm using says they > have a 2.2k on the base. Quoting from the datasheet, "The SN75468 has a > 2700-Ω series base resistor for each Darlington pair for operation directly > with TTL or 5-V > CMOS." -- 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 https://groups.google.com/groups/opt_out.
