VCC is 240V. Anode obviously sees less, plus I tried clamping the Darlington outputs to, say, 70V with limited success. The voltage divider I used for this needed to have low value resistors to have any noticeable effect, so quite a lot of current through the divider, except no measurable current into the COM pin.
All in all, thoroughly confusing, but I’m happy with the BS107P. I’ve run out of bench space for my old Tektronix scope, I need to get a more up to date one. > On Apr 29, 2020, at 12:12 AM, gregebert <[email protected]> wrote: > > > > I suspect that leakage current is causing the Darlington driver (2-stage high > current-gain amplifier) to turn on. With a base resistor (see datasheet), any > leakage current into the base can still get amplified, because some of it > will leak into the Darlington-pair and get amplified. A scope will give you a > good idea what the leakage looks like; could be a series of "glitches" when > the bulb turns on for a short time. > > With no base resistance, all leakage-current into the base gets shunted away > so it never gets amplified. > > How high is your VCC supply for the neon bulbs ? It's certainly well-above > the 100V spec for the driver, and despite the voltage-drop across the tube, > there are occasional higher-energy electrons that can go thru the tube with a > lower-than-normal voltage drop and they will greatly increase the leakage > current. > -- > You received this message because you are subscribed to a topic in the Google > Groups "neonixie-l" group. > To unsubscribe from this topic, visit > https://groups.google.com/d/topic/neonixie-l/_TX-Z5A27JQ/unsubscribe. > To unsubscribe from this group and all its topics, send an email to > [email protected]. > To view this discussion on the web, visit > https://groups.google.com/d/msgid/neonixie-l/e6f2268a-78d8-4a3d-af13-eef837bbdb5e%40googlegroups.com. -- 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 view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/0C5896F9-4D64-4542-9330-0C95D05AD1C9%40gmail.com.
