Re: [time-nuts] Trimble Thunderbolt GPSDO Troubleshooting

All, Okay, those two parts worked! The 5V reference plus replacing that opamp repaired the unit to working. Amazing accuracy when my counter is at a 10sec gate (off by all of 0.5hz, which is well within my uncertainty of my counter (Racal-Dana 1992)). Also of interest is the unit went from

Re: [time-nuts] Trimble Thunderbolt GPSDO Troubleshooting

All, Just to answer my own question: The output (Pin 6) of U15 (LT1021DCS8-5) goes to what looks like R83 (that whole section has a lot of confusing labeling), then to Pin 3 of U17 (LT1014), which is the positive input of the A amplifier. That then comes out of Pin 1 (A’s output), and goes

Re: [time-nuts] Trimble Thunderbolt GPSDO Troubleshooting

Hi Charles (et al), So, I did see that post, but I'm not entirely sure how it works. If I understand, the FPGA is generating the 9.7khz clock (which I can see on the test pad he indicated), running it through some logic to square it up, then a low pass filter, then into the op-amp similar to

Re: [time-nuts] Trimble Thunderbolt GPSDO Troubleshooting

> Stewart Cobb described the operation of the DAC > (actually, PWM) in a post on Nov 2, 2013 > ("Subject: [time-nuts] Thunderbolt tuning DAC > theory of operation"). Check the list archive. https://www.febo.com/pipermail/time-nuts/2013-November/081058.html /tvb

Re: [time-nuts] Trimble Thunderbolt GPSDO Troubleshooting

Ryan wrote: Also confusing is the quad op-amp seems to be saturated at the negative rail. I can see this Opamp feeds the adjust pin on the OCXO, but I’m not sure what feeds it. Guessing the FPGA? I still can’t find the DAC… all I see are these pictures [ ] but the pictures aren’t of the

Re: [time-nuts] Trimble Thunderbolt GPSDO Troubleshooting

an Stasel" <rsta...@uoregon.edu<mailto:rsta...@uoregon.edu><mailto:rsta...@uoregon.edu>> To: "Discussion of precise time and frequency measurement" <time-nuts@febo.com<mailto:time-nuts@febo.com><mailto:time-nuts@febo.com>> Subject: Re: [time-nuts] Trimb

[time-nuts] Trimble Thunderbolt GPSDO Troubleshooting

Well, if you think the 5V ref is bad, you could pull the ref chip and jumper the logic 5V to its output pad (through a resistor... maybe 1K) to do a quick and dirty test. If the resistor output is dragged down, you know something is loading down the ref voltage.

Re: [time-nuts] Trimble Thunderbolt GPSDO Troubleshooting

to:rsta...@uoregon.edu>> To: "Discussion of precise time and frequency measurement" <time-nuts@febo.com<mailto:time-nuts@febo.com><mailto:time-nuts@febo.com>> Subject: Re: [time-nuts] Trimble Thunderbolt GPSDO Troubleshooting Hi Bob, I think I’m going

Re: [time-nuts] Trimble Thunderbolt GPSDO Troubleshooting

sel" <rsta...@uoregon.edu<mailto:rsta...@uoregon.edu><mailto:rsta...@uoregon.edu>> To: "Discussion of precise time and frequency measurement" <time-nuts@febo.com<mailto:time-nuts@febo.com><mailto:time-nuts@febo.com>> Subject: Re: [time-nuts] Tri

Re: [time-nuts] Trimble Thunderbolt GPSDO Troubleshooting

Stasel" <rsta...@uoregon.edu> > To: "Discussion of precise time and frequency measurement" > <time-nuts@febo.com> > Subject: Re: [time-nuts] Trimble Thunderbolt GPSDO Troubleshooting > > Hi Bob, > > I think I’m going to take a look, since I co

Re: [time-nuts] Trimble Thunderbolt GPSDO Troubleshooting

Hi Bob, I think I’m going to take a look, since I couldn’t find a spare, so I’ve got a couple on order (and a few days to wait). So, looking at the datasheet (http://www.intersil.com/content/dam/Intersil/documents/icl2/icl232.pdf), you’re saying check the two caps across pins 1 and 3, and 4

Re: [time-nuts] Trimble Thunderbolt GPSDO Troubleshooting

Personally I'd take a few minutes to look closer at the '232 chip with the scope. Are the charge pump caps swinging 5V p-p and 10V p-p? if not swinging at all, trash the chip. Is -V pin voltage about equal to the negative of the +V pin? If so, that's OK. If not might have an output shorted, or

Re: [time-nuts] Trimble Thunderbolt GPSDO Troubleshooting

That 232 chip should run at near as damnit ambient so I'd say it's highly likely to be dead. Replacement should be a doddle On 25 Mar 2016 19:02, "Ryan Stasel" wrote: > All, > > I recently got an (obviously used) Trimble Thunderbolt (case says Rev B). > Hooking it up to my

[time-nuts] Trimble Thunderbolt GPSDO Troubleshooting

All, I recently got an (obviously used) Trimble Thunderbolt (case says Rev B). Hooking it up to my bench PS, I got the unit fired up, and the OCXO relatively rapidly settled down to just over 26hz over 10Mhz (According to my Racal-Dana 1992, which I’ve found to be EXTREMELY accurate compared