It is not the transistor that keeps conducting or leaking. The voltage you see at the anode comes from leakage from floating cathodes from the other tubes. What you can do to kill the ghosting is connecting 10 diodes to all tube cathodes. Connect the anodes of the 10 diodes to the 10 cathodes of the tubes. Tie all cathodes from these diodes together, and connect that to a voltage divider made of 2 resistors of 10k, between your 180v supply and ground. That should kill any ghosting...
Op do 18 jan. 2018 om 19:15 schreef Tomasz Kowalczyk <ten.ko...@gmail.com> > I've checked the driving circuit before posting with oscilloscope and > there is absolutely nothing incorrect visible up to MMBTA92s collectors. > I've taken photos of the bases of PNP transistors - the signal is clean, as > visible below: > > <https://lh3.googleusercontent.com/-e7kYKgtZ5g0/WmDgB921u-I/AAAAAAAAC4k/MnGzGEuIcqoi4-QkLHEddY0fCnSVnM5MQCLcBGAs/s1600/IMG_20180118_184655%255B1%255D.jpg> > > > > > > > > > > > > > > There are only three channels shown, because I've actually shorted > something while soldering pieces of wire to the bases, so one of the > transistors ended up its life in a spectacular and loud way :) and I can't > find the bag with more of these. So I desoldered it. > So, if there was a problem with capacitive coupling between wires leading > to the board, some loose connections or capacitive coupling, it should be > visible in here. All the bad stuff happens INSIDE of the MMBTA92s. > This is the signal at anodes of the tubes: > > > <https://lh3.googleusercontent.com/-Sv6-DkDwlzk/WmDg1enXQCI/AAAAAAAAC4s/UJbkcWqalqAnD9EcIRJqnA2AS_Um-IHbQCLcBGAs/s1600/IMG_20180118_185202%255B1%255D.jpg> > > > > > > > > > > > > > > As you can see, there is no glitch while the channel with removed PNP > transistor should be on, so it again narrows the problem to PNP transistor > - if any other part of the circuit would be the one creating glitches, the > glitch would happen at this time as well. > I've also added 10nF decoupling directly to HV input pins of my PCB, with > no effect. Noise on HV rail is about 30mVpp and doesn't look like it is > correlated with switching frequency. > > I'm starting to think that I might have received a bad batch of > transistors or they are just counterfeit - which would be sad news, because > I consider the supplier (TME) as rather reliable. > > -- > 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 neonixie-l+unsubscr...@googlegroups.com. > To post to this group, send email to neonixie-l@googlegroups.com. > To view this discussion on the web, visit > https://groups.google.com/d/msgid/neonixie-l/831d7192-f611-4b27-87c9-ac988c059ac4%40googlegroups.com > <https://groups.google.com/d/msgid/neonixie-l/831d7192-f611-4b27-87c9-ac988c059ac4%40googlegroups.com?utm_medium=email&utm_source=footer> > . > For more options, visit https://groups.google.com/d/optout. > -- Vriendelijke groeten, Frank Bemelman Frank Techniek Vennestraat 11X 2161LE Lisse Telefoon +31 252 425 772 -- 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 neonixie-l+unsubscr...@googlegroups.com. To post to this group, send an email to neonixie-l@googlegroups.com. To view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/CAEhU539dhxvRU-kUGod-JtC11zr3Sw-s3RGb7ET%2B6oTLXBZx4w%40mail.gmail.com. For more options, visit https://groups.google.com/d/optout.
