Is there a Z-axis ??? That would be my first suspect; if the trace is still visible, then the appropriate grid needs to be driven a bit more negative.
If the CRT uses rapid movement for dark (technically dim) regions, and slower movement for bright regions, then my best guess is some kind of software tweak would be needed to get the beam to move faster, or off the phosphor-coated area (or both). On Saturday, June 22, 2024 at 3:49:04 AM UTC-7 Dekatron42 wrote: > Can you remove the processor and feed the amplifiers directly from a > potentiometer connected to NEG5 and POS5 and see how the dot moves on the > screen? You need one potentiometer for X & Y so that the dot will appear on > screen. This way you will test out the amplifier chains without the DAC > involved. > > /Martin > > On Saturday 22 June 2024 at 12:10:54 UTC+2 Max DN wrote: > >> Martin, that's what I am thinking... however I don't think it's the >> amplifier chain as I get the same issue if I just display X and Y signals >> straight out of the DAC on the oscilloscope. That brings it down to a few >> components only: 2 potentiometers for centerting X and Y, their two bypass >> capacitors, the DAC and its 1 bypass capacitors, the +3.3V Linear >> regulator, the +5V supply to the DAC. I'm going to try and replace >> everything once more by one by one... Not the smartest way of doing it but >> let's see what it brings... >> >> Il giorno sabato 22 giugno 2024 alle 11:01:12 UTC+1 Dekatron42 ha scritto: >> >>> Could it be the that any of the power lines sags as the signal tries to >>> increase to the right (in the picture right where the line is) or that any >>> of the resistors in the amplifier chain has an incorrect value? >>> >>> /Martin >>> >>> On Saturday 22 June 2024 at 11:32:21 UTC+2 Max DN wrote: >>> >>>> Tried to replace a few more parts, including potentiometers for Focus >>>> and Intensity, made no difference. So, back to basics: using an >>>> oscilloscope I see that the X and Y signals straight out of the DAC look >>>> exactly the same as in the picture I had attached. Maybe a faulty DAC? >>>> Tried to replace the DAC twice with new ones and made no difference. Looks >>>> like I'm hitting some sort of physical limits... More debugging to do... >>>> >>>> Il giorno venerdì 21 giugno 2024 alle 18:31:51 UTC+1 Max DN ha scritto: >>>> >>>>> Hello, >>>>> >>>>> I'm building a scope clock, same board as another one I built before >>>>> with no issues (after some help I got on this group, thank you!) and I'm >>>>> getting a flat line on the display. >>>>> >>>>> I have tried replacing the CRT, the DAC, the Op Amps and the MPSW42 >>>>> deflection amplifiers but made no difference. CRT is 3RP1A. Code and >>>>> circuitry have been fully tested on another working board. >>>>> >>>>> I do recall having a similar issue before with a DH3/91 CRT and I seem >>>>> to recall that I just needed to adjust the pot for Astigmatism that >>>>> controls the voltage on A2. Schematics as in here: >>>>> http://www.cathodecorner.com/sctv/sctv-schem-2.png >>>>> >>>>> I'm a bit at a loss here, although I'm sure it's something simple that >>>>> I'm missing. >>>>> >>>>> Pic attached. >>>>> >>>>> Any suggestions welcome, >>>>> >>>>> Max >>>>> >>>> -- 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/3ec834bd-f38d-41d2-8a5d-31bc762da9e4n%40googlegroups.com.
