Josh, I looked at one of the REX boards I had that didn't work. The regulator was getting hot on it and I had the same low resistance measurements on the VCC and ground. I know on this particular one I killed the CPLD by shorting the FTDI VCC and ground when jumping VCC to R3.
Brian On Oct 18, 2017 7:22 PM, "Brian White" <bw.al...@gmail.com> wrote: > I guess if you're going to build over 60 of them it starts to matter. I > just figured if I'm going to go to this much effort it took just to build > one at all, that $1 wasn't even visible, but a built and in-use rex that > fails some day when it might have lived, is visible. So I went for the > better-ish versions of all parts. The factors for this are not the same as > for mass producing a clock that will sell in dollar stores. > > On Wed, Oct 18, 2017 at 6:39 PM, Stephen Adolph <twospru...@gmail.com> > wrote: > >> Commercial is fine.... >> >> >> On Wednesday, October 18, 2017, Josh Malone <josh.mal...@gmail.com> >> wrote: >> >>> Also, meant to ask: >>> >>> Brian's BOM includes the Industrial variant of the CPLD. The >>> commercial variant is almost $1 cheaper and seems well within >>> tolerance >>> >>> (voltage min is 3 instead of 2.7, temp is 0 - 70 C instead of 40 - 85 °C) >>> >>> >>> Any reason not to sub this part in? >>> >>> -Josh >>> >>> On Wed, Oct 18, 2017 at 4:56 PM, Josh Malone <josh.mal...@gmail.com> >>> wrote: >>> > Thanks. I'm going to just order new parts and try again. >>> > >>> > On Wed, Oct 18, 2017 at 4:49 PM, Brian Brindle <bbrin...@gmail.com> >>> wrote: >>> >> 11.7k on 2 of mine. >>> >> >>> >> >>> >> On Oct 18, 2017 4:25 PM, "Stephen Adolph" <twospru...@gmail.com> >>> wrote: >>> >>> >>> >>> I can try to measure it later today for you. >>> >>> >>> >>> On Wed, Oct 18, 2017 at 4:24 PM, Stephen Adolph < >>> twospru...@gmail.com> >>> >>> wrote: >>> >>>> >>> >>>> either the chip is a dud, or you have soldered it down in the wrong >>> >>>> orientation (which is kinda easy to do)... Do you have more CPLDs? >>> >>>> >>> >>>> On Wed, Oct 18, 2017 at 4:22 PM, Josh Malone <josh.mal...@gmail.com >>> > >>> >>>> wrote: >>> >>>>> >>> >>>>> Thanks for the leads. >>> >>>>> >>> >>>>> I removed the CPLD and the resistance from 3v3 to gnd went to open; >>> >>>>> repopulated it and it went to 3-ohms. Dunno what to try next. Maybe >>> >>>>> put the same CPLD back on an original REX board (non-castellated) >>> and >>> >>>>> see what happens. But, I'd *really* love for someone to measure the >>> >>>>> resistance on a known-good REX board and let me know what it should >>> >>>>> be. Assuming the CPLD draws <= 1ma (datasheet says 17uA standby), R >>> >>>>> should be over ~3k. >>> >>>>> >>> >>>>> -Josh >>> >>>> >>> >>>> >>> >>> >>> >> >>> >> >
