[time-nuts] No 1 PPS output on a Tbolt

Bruce Griffiths bruce.griffiths at xtra.co.nz
Mon Feb 8 01:17:08 UTC 2010


The PPS driver appears to use at least  3  inverters from a 74AC04 (U19) 
connected in parallel with a small series resistor between the parallled 
inverter outputs and the PPS connector.
Open the case and check the waveforms at the 74AC04 inputs and outputs.
Check the series resistor for continuity, also check the solder joint 
between the BNC inner conductor and the PCB.

Bruce

Bruce Griffiths wrote:
> Any idea what the pulse shapes you see is with a 1M load and with a 50 
> ohm load?
>
> Bruce
>
> SAL CORNACCHIA wrote:
>> Hi Didier,
>>   When the 50 ohms termination is switch on the oscilloscope there is 
>> a tiny positive dot deflecting every second, it appears to have a 
>> very low output.
>>   Best regards,
>> Sal C. Cornacchia
>> Electronic RF Microwave Engineer (Ret.)
>>
>>
>>
>>
>>
>>
>>
>> ________________________________
>> From: Didier Juges<didier at cox.net>
>> To: Time-Nuts<time-nuts at febo.com>
>> Sent: Sun, February 7, 2010 11:51:15 AM
>> Subject: Re: [time-nuts] No 1 PPS output on a Tbolt
>>
>> The pulse is narrow, but it should be a full 5V amplitude. The driver 
>> is pretty beefy, the amplitude does dot drop appreciably when loaded 
>> with 50 ohms on mine.
>>
>> Didier KO4BB
>>
>> ------------------------ Sent from my BlackBerry Wireless thingy 
>> while I do other things...
>>
>> -----Original Message-----
>> From: SAL CORNACCHIA<salccor at rogers.com>
>> Date: Sun, 7 Feb 2010 08:42:49
>> To: Discussion of precise time and frequency 
>> measurement<time-nuts at febo.com>
>> Subject: Re: [time-nuts] No 1 PPS output on a Tbolt
>>
>> Hi Bob,
>> The pulse is barely visible on the Tektronix 485 it appears to be a 
>> very low output.
>> Best regards,
>> Sal C. Cornacchia
>> Electronic RF Microwave Engineer (Ret.)
>>
>>
>>
>>
>>
>>
>>
>> ________________________________
>> From: Bob Camp<lists at cq.nu>
>> To: Discussion of precise time and frequency 
>> measurement<time-nuts at febo..com>
>> Sent: Sun, February 7, 2010 11:26:16 AM
>> Subject: Re: [time-nuts] No 1 PPS output on a Tbolt
>>
>> Hi
>>
>> The 5345 should see it if it's set to 50 ohm termination and DC 
>> coupling.. A
>> sweep of the trigger from about 1.5 to 3.5 volts should show it there 
>> over
>> most of the sweep.
>>
>> Bob
>>
>> --------------------------------------------------
>> From: "SAL CORNACCHIA"<salccor at rogers.com>
>> Sent: Sunday, February 07, 2010 11:06 AM
>> To: "Discussion of precise time and frequency measurement"
>> <time-nuts at febo..com>
>> Subject: Re: [time-nuts] No 1 PPS output on a Tbolt
>>
>>> Oscilloscope and 5345A Counter, the Tbolt software shows all green.
>>>    Best regards,
>>> Sal C. Cornacchia
>>> Electronic RF Microwave Engineer (Ret.)
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>> ________________________________
>>> From: "Stan, W1LE"<stanw1le at verizon.net>
>>> To: Discussion of precise time and frequency measurement
>>> <time-nuts at febo.com>
>>> Sent: Sun, February 7, 2010 10:47:42 AM
>>> Subject: Re: [time-nuts] No 1 PPS output on a Tbolt
>>>
>>> Hello Sal,
>>>
>>> What are you monitoring the PPS output with ??
>>>
>>> It is a short duration pulse.
>>>
>>> What does the TboltMON software (available at the trimble website) 
>>> show ?
>>>
>>> What does Lady Heather indicate ?
>>> (She is just waiting to massage your numbers.)
>>>
>>> Stan, W1LE
>>>
>>>
>>>
>>
>






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