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 neonixie-l+unsubscr...@googlegroups.com. To view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/de838879-2973-42b8-9753-ef5f95d99eddn%40googlegroups.com.
