I checked that schematic and as you say 1W resistors performing in the exact same way that the latter design does. I'll forge ahead with the current plan - I am using 2 x 5W parts in parallel (to get the required resistance whilst sharing the load) which get only very slightly warm! - Richard
On Monday, 3 November 2025 at 18:56:12 UTC Dekatron42 wrote: > The instructions from The Burroughs kit for the BG12205 is in this thread > (I cleaned the original up a bit and it is in the last post) where they use > 1W resistors. > > https://groups.google.com/g/neonixie-l/c/9QE680EzaTc/m/_LUcA8coBAAJ > > /Martin > > On Sunday, 2 November 2025 at 06:46:35 UTC+1 Richard Scales wrote: > >> Hello and thank you for your pointers - right now, the display seems to >> be running evenly and looks good - no significant heat is being generated >> in the electronics though presence of a bunch of 5W resistors seems somehow >> out of place when the display should only be using mA ! >> - Richard >> >> >> On Friday, 31 October 2025 at 23:27:28 UTC Dekatron42 wrote: >> >>> I've dug through my documents and I've been thinking about that 1M >>> resistor in the cathode keep alive electrode and its effect on the driving >>> of these tubes and I think it is an error to have it there as, even though >>> it will only flow a very low current through it, it will affect the common >>> ground point for all of the driving circuits and that will affect the level >>> depending on how many bars that are lit up. I've never seen a circuit that >>> incorporates that 1M resistor in the keep alive electrode for the cathode >>> and thinking about it it looks incorrect. >>> >>> Please correct me if I am wrong but that is my opinion on how these >>> tubes should be driven. >>> >>> /Martin >>> >>> On Friday, 31 October 2025 at 13:26:11 UTC+1 leo oel wrote: >>> >>>> IGT1-203 Self Scan bar graph display >>>> >>>> https://dotdisplay.blogspot.com/2017/08/igt1-203-self-scan-bar-graph-display.html >>>> >>>> пятница, 31 октября 2025 г. в 12:27:23 UTC+2, Dekatron42: >>>> >>>>> There are few professional designs in the audio business and in the >>>>> ventilation flow control business who completely skip that extra 68V >>>>> supply >>>>> - I haven't checked the data-sheet what it says but they don't bother >>>>> with >>>>> that extra voltage. Some designs use a SN75468/9 IC (75469 in case of >>>>> CMOS >>>>> and 75468 if TTL is used) instead of transistors and no pull-up >>>>> resistors, >>>>> just hook the 68V signal to the common pin on the SN75468/9. >>>>> >>>>> For all of the designs I've seen there is not one that uses a 1M >>>>> resistor on the keep alive cathode, only on the anode, they all just >>>>> ground >>>>> the keep alive cathode pin directly. >>>>> >>>>> Some designs uses a voltage between 50-80V for the 68V voltage. Some >>>>> designs uses a voltage doubler/tripler to supply all voltages from a low >>>>> voltage AC transformer, so maybe use a switcher with say 62.5V DC output >>>>> and the quadruple that to 250V DC if there is the possibility of hooking >>>>> into the circuit before rectification/smoothing? >>>>> >>>>> /Martin >>>>> On Friday, 31 October 2025 at 06:57:04 UTC+1 Richard Scales wrote: >>>>> >>>>>> Does anyone have any experience in driving these panaplex-like >>>>>> bargraph displays? >>>>>> >>>>>> I have some IGT2-203R and am using a well publicised circuit from >>>>>> here: >>>>>> https://stromrichter-org.translate.goog/attachment.php?aid=4116&_x_tr_sl=auto&_x_tr_tl=en&_x_tr_hl=en-US&_x_tr_pto=wapp >>>>>> >>>>>> [image: Pic1.jpg] >>>>>> >>>>>> I have made various changes, I'm using an Arduino Nano for the >>>>>> controller, an HV module for the 245V and I changed out the R2/D2 >>>>>> combination for an LR8 HV regulator as I found that R2 was getting a lot >>>>>> warmer that I would like. >>>>>> >>>>>> Now I am looking at the anode supply which is controlled by R8+R18 (I >>>>>> am only using one channel so don't have R7/R17. >>>>>> >>>>>> It seems that when Q8 is off, the Anode is connected to the 245 >>>>>> supply via 36K for current limiting purposes - that's all good. When Q8 >>>>>> is >>>>>> on, then the anode is fed from what is now the voltage divider >>>>>> combination >>>>>> of R8+R18 (98V) - also good. >>>>>> >>>>>> However, that combination of 24K+36k is drawing about (245/60)mA - >>>>>> 4mA - the power being almost 1W - so they get a little warm. I have over >>>>>> specified and used 5W parts. >>>>>> >>>>>> What I have works just fine, and, in fact I even doubled up on the >>>>>> resistors to share the load even further but I wonder if there is >>>>>> perhaps >>>>>> a better way which might not generate quite so much heat? >>>>>> >>>>>> It might seem overkill but I could make 98V using another LR8 and >>>>>> then use high side drivers to 'switch' between the two (like a couple of >>>>>> Opto Couplers or a bunch of 42/92 transistors). >>>>>> >>>>>> ... or am I being over cautious? >>>>>> >>>>>> - Richard >>>>>> >>>>>> -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. 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