On 14 sty 2012, at 18:37, marta_kson wrote: > The PCB is very hard to follow with those dreadful colors, Eagle?
Yes, sorry about that. But Eagle is the only low cost (or free) option for hobbyists and it isn't bad for simple designs. > The FB trace is definitely no good. It's imperative to keep it just as > a minimum pad right at the chip with just the two resistors connected. Hmm. To make the low voltage part of the FB trace any shorter, I'd need to get rid of the potentiometer. Otherwise it can't be made any shorter, the resistors can't be physically closer to the chip. [time passes] Well, after several experiments it turned out that after removing the pot and shorting it with a horizontally-laid piece of wire everything works just fine. So it seems that the pot (a Bourns 3296-style multi-turn potentiometer, about 1cm of height, as in http://www.bourns.com/pdfs/3296.pdf) was picking up interference. Could that be because of its vertical design? But I'd like to better understand the comments (yours and Nick's) about the FB trace being too long. I thought that the critical part of that trace is the low-voltage part, from the resistor divider towards the FB pin. In my design the "long" part is actually just HV. I did not consider that to be very sensitive to EMI, as any voltage picked up here gets attenuated 20x or so by the resistor divider. Am I right? The length of the HV trace to the resistor divider isn't different in my design and in Nick's design. It's just that I placed the output connector at the top of my board, while Nick has it on the bottom. But it's the same HV and it still needs to go around the whole chip and RSENSE resistor in particular. I could eliminate one row of vias next to RSENSE, which would make that trace 1mm shorter, but is it really worth the effort? I think I'll need to redesign the board without the potentiometer, thus bringing the FB resistors much closer to the chip. --J. -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. To post to this group, send an email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/neonixie-l?hl=en-GB.
