Both transistors are rated for 500mA, so I don’t see why you need a MJE340 for an IN-9. This is particularly relevant for me as I want to switch around 50mA using 3.3V. Not sure what the voltage is right now, given that this is the cathode.
> On Apr 22, 2020, at 5:25 PM, Mac Doktor <[email protected]> wrote: > > On Apr 22, 2020, at 9:39 AM, '[email protected]' via neonixie-l > <[email protected]> wrote: >> >> I would say whichever is cheaper, keeping in mind that nothing is cheaper >> than free from the junque box. I used the floor sweepings (advertised as >> npn 300V and 10W) from Poly Paks, and none of these have failed yet. I did >> have one genuine Motorola MPSA92 fail after 40 years of service. Just make >> sure you are driving your transistors into saturation. Obviously TO92 is >> smaller than TO220, and this might be a factor in your application. > > > The perfect example of this is driving an IN-13 vs an IN-9. The former will > work with an MPSA42 but the latter requires an MJE340 because of the higher > current. It's well known that the bargraph tubes work more reliably if > they're strobed; all of the circuit examples in Russian data sheets for the > IN-9 and IN-13 use a half-wave rectified 220V mains power source. And now I > finally understand a circuit modification I saw in a forum thread that has > puzzled me for some time. The OP couldn't get an IN-9 (using an MJE340 of > course) to work reliably using a generic barpgraph driver circuit. One of the > replies added a 555 running at 50Hz driving a MPSA42 in series with the > MJE340. What? How could you use the smaller trans... Now I get it. The MPSA42 > was being used as a switch. DUHH. > > Thank you for that insight. Cue up the next great mystery of life... > > > Terry Bowman, KA4HJH > "The Mac Doctor" > > https://www.astarcloseup.com/ > > "Every kid starts out as a natural-born scientist, and then we beat it out of > them. A few trickle through the system with their wonder and enthusiasm for > science intact."—Carl Sagan, Psychology Today, 1996 > > -- > 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/B30CB5AB-765F-4F1C-AC1C-8F7D176739EE%40gmail.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/2B974D07-C761-433F-940A-410F98EC4823%40gmail.com.
