[time-nuts] thunderbolt fault
lists at rtty.us
Sat Feb 27 01:55:57 UTC 2010
Depending on the supply setup, a common mode choke might also be a good idea.
The +12 runs the OCXO, so it's going to have an impact.
What about the +5 Volts? Obviously it needs to be crud free. Gross changes will impact the temperature of the unit. What about small changes? Is it running the maser reference for the DAC or does that come off the +12? Is +5 just a digital supply?
Lots of questions ....
On Feb 26, 2010, at 6:59 PM, WarrenS wrote:
> Yes, I Did that, The +5 and -12 has NO effect on freq or operation of the unit except for really far out voltages.
> I tested mine with the -12 from -2 to -15 and could see no effect in the e-11 range.
> The -12 is used for the RS232 and the -Dac out so If you don't need the neg Dac out voltage or neg RS232 Drive, then it can pretty much be anything. But It should be kept in -7 to -13 range, and common sense means there should be little noise on it so it does not couple into other things. BUT the circuit it's self does not care what the supply is at or what is used.
> The +12 on the other hand, Needs to be stable and quiet with no ripple.
> I found using a +15 volt supply feeding a 12V three terminal will heat slinked regulator a good way to go to keep ALL the ripple out of the +12V
> Has anybody actually measured the supply sensitivity on the -12 volt line to see weather a 5 volt change makes any noticeable difference in the output frequency? The power on -12 is very low, so there should be negligible thermal impact from a change.
> On Feb 26, 2010, at 4:52 PM, George Dubovsky wrote:
>> The -12 can be anything from -7 to -12V and it will work. The units that
>> were removed from Grayson or Andrew equipment had a zener diode changed on
>> the Thunderbolt (by Trimble) that kept the power alarm from being invoked at
>> low values of this voltage.
>> geo - n4ua
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