[time-nuts] thunderbolt fault
warrensjmail-one at yahoo.com
Sat Feb 27 03:44:24 UTC 2010
I don't know of any reasonable inductor thing that is useful to reduce High
current ripple PS ripple.
There where inductors, of the small bread box size, used in very early tube
radios, But that was mostly just for low current B+ voltages.
Do you have a standard part in mind that will reduce 60 and 120Hz line
voltage ripple by 20 dB or more at 1/2 amp rating,
AND that does not hurt the voltage regulation with changing currents?
What about one to reduce the DC voltage variations?
Your ground loop comment, sounds like you are talking about isolating the 10
MHz Osc ground to reduce ground loop problems and your comments are NOT
about reducing the +12 volt PS ripple. If so, Yea good idea, But BIG
As often happens on these post, there is misunderstandings somewhere and
they tend to get way off the point,
so have to go now and let others take the torch.
Original question was, Is the Tbolt's -12 volt supply sensitive or critical.
SIMPLE answer, NO, just use a little common sense with it.
It's pretty easy to get a common mode choke that will indeed break up 120 Hz
ground loops. Often they are very low impedance. With most supplies the
rectified line is what's coming through.
On Feb 26, 2010, at 10:10 PM, WarrenS wrote:
>>> Common mode choke filter does not get ride of LINE NOISE on the +12 V or
>>> LINE VOLTAGE sensitivities...,
>> Please explain how a common mode choke on the +12 and ground does nothing
>> to help keep the supply clean.
> What size is your common mode choke filter?
> To have any effect on 60 Hz PS ripple it would need to bigger than a
> (small) bread box .
> And to help reduce DC type line voltage variations it would need to be
> bigger than a planet. (yea, Earth size)
> Common mode filters are for HI freq, not 60 Hz OR DC.
> But then, you already know that so I do not know why your comment???
> Please explain how a common mode choke on the +12 and ground does nothing
> to help keep the supply clean.
> On Feb 26, 2010, at 9:57 PM, WarrenS wrote:
>>> Lots of questions ....
>> Same Simple answer.
>> Make the +12 volts is as good as you can get it, For the rest any general
>> purpose PS works fine.
>> And a Common mode choke filter does not get ride of line noise on the +12
>> V or Line voltage sensitivities, both are important on the +12V
>> Depending on the supply setup, a common mode choke might also be a good
>> 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
>>> 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.
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