Hi > On Dec 16, 2016, at 3:21 AM, Pete Stephenson <[email protected]> wrote: > > On 12/15/2016 7:45 PM, Charles Steinmetz wrote: >> Tom wrote: >> >>> There's something very odd going on here, either with Pete's TBolt, >>> and/or with Mark's Heather v5. >>> >>> 2) It also shows some truly erratic behavior the last day and a half, >>> with multiple, massive, sudden temperature drops going down several >>> degrees. I've never seen this. >> >> I think the more revealing trace is the DAC voltage. There are ~70mV >> plunges, to a dead quiet (at this scale), more negative value. 70mV is >> huge, corresponding to a -35e-9 frequency shift (350mHz). If the DAC >> voltage actually changed that much, it would pull the OCXO so far off >> frequency during these events that it would take much, much longer than >> shown (indeed, much longer than the width of these events) to >> re-stabilize. Yet we see clean jumps within seconds, and no settling. >> (Unfortunately, the Tbolt's estimation of frequency is not plotted on >> the posted screen shot.) > > Apologies, I did have the frequency plot turned off. I've taken some > more screenshots with the frequency plot turned on. > > screenshot.png is a close-up of one of the odd spikes, while > screenshot2.png took place ~10 minutes later (I just scrolled to the right). > > The small frequency jumps in screenshot2.png are due to satellites > entering and leaving the field of view. Due to the setup of my > apartment, the antenna location is decidedly sub-optimal and has a clear > view only to the northwest. > >> I find it hard to believe that LH does much processing of the reported >> DAC voltage, so I think it's safe to say (1) the LH plot shows >> accurately what the Tbolt is reporting (at least WRT the DAC voltage), >> and (2) the actual DAC voltage is not doing what the Tbolt is reporting. >> >> Looks like a sick Tbolt to me. > > Any idea what might be the issue? I can do SMT rework to replace a bad > temperature sensor or other faulty chips, within reason (super-fine > pitch stuff is a pain).
With multiple things going nuts at the same time, power would be the first thing on my list. Second would be the serial i/o stuff. In both cases things like connectors and cables are very much on the suspect list. Bob > > Cheers! > -Pete > >> Best regards, >> >> Charles >> >> >> _______________________________________________ >> time-nuts mailing list -- [email protected] >> To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. > > <screenshot.png><screenshot2.png>_______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
