@Martin, if I try to bypass the DAC using POTs for NEG5 and POS5 it all seems fine (the dot goes across the whole X axis and Y axis). @gregebert, no Z-axis.
I am probing X and Y just out of the DAC and not connected to anything else. I can see the image on the oscilloscope as a full round circle, but as I try to center it to what would be the center of the CRT then thr circle flatlines. It feels as though past a certain point on the vertical axis, the dots are just collapsing into the same line and cannot go past (on one end of the Y vertical axis, X axis is fine). Very odd as I have already used same code and same pcb for another scope clock. After 10 hours on it today, I'm going to let go until I have any other ideas. I have tried replacing the processor, the DAC (3 times), checked all resistors and bypass caps and triple checked all soldering points. Maybe it's time to bin this pcb, but I do like a challenge! Il giorno sabato 22 giugno 2024 alle 16:38:19 UTC+1 gregebert ha scritto: > 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/1606bd51-479f-4ad4-af48-5f9d1067b15bn%40googlegroups.com.
