Bob wrote:

No, but I often view things that don't do the job they need to do as
crap, especially if they are offered in such a way as to suggest that
they are, in fact, useful for the intended purpose.  So, let's take the
proposed power supply -- a switching regulator to develop +5v and -12v
supplies from an existing +12v supply, with noise of 35mVp-p, offered
specifically as a power supply solution for Tbolt GPSDOs.  If the
offering said explicitly that a Tbolt can't provide its best performance
with the product because of its high noise level, then I might be on the
fence about whether it was "crap."  But if it were offered as a power
supply for Tbolts with no mention of what I consider to be a large
departure from acceptable performance for the intended use, then yes,
I'd probably consider it "crap."

The issue is that many users do not know what the relevant needs are.
Rightly or wrongly, they are relying on suppliers to do that job for
them.  So, offering something for a particular use carries the
implication that it is really useful for that purpose.  If a seller
tells a time-nut that a power supply is designed to run a Tbolt, an
implicit representation has been made that it will work in that role as
a time-nut would expect it to.  But IMO, the proposed product would not
do so because of the high noise level.

So, what distinguishes this from packages that have been sold to
time-nuts in the past that included power supplies that also did not
work in that role as a time-nut would expect?  In those cases, due
largely to this list, there was widespread discussion of the issue and
equally widespread knowledge that for time-nuts-quality results, the PS
that came with the package needed to be replaced with something better.
So at this point, if someone offers a PS to time nuts for use with
Tbolts, it would be natural to assume that the seller was familiar with
that history and was offering the "something better."  So today, if that
is not the case, it should be stated explicitly.

Best regards,

Charles

When I began the design process, I assumed - as would be reasonable - that ~30 mV P-P of noise and ripple were acceptable for input power supplies, and that before they were used for a precision purpose within the device that there would be further filtering if for no other reason that you’d think they’d want to limit coupled interference on the power lines. My assumption, given the extremely low draw on the -12 line was that they were using the -12 line just for the RS-232 level shifter (and that they were too lazy to use a MAX232 like everybody else).

Now that I’ve posted and had my assumptions disabused, I’ll need to go back to the drawing board for another attempt. The price point won’t likely be $25 anymore, but the question was whether anyone wanted a Tbolt power supply, and if I offer anything at all, I intend for it to be reasonably useful for its intended purpose. Like all the things I make for sale, it will be open hardware, which will afford everyone here more than enough opportunity for Monday morning quarterbacking. :)

Hi

It is not that hard to do. Use a linear rather than a switching approach. Run the +12 and +5 supplies off of LT1764 regulators. The -12 is very low current, run it off of a low noise op amp. There are lots of toroidal line transformers that will drive something like this.

Bob

I bought a module off ebay for a project recently.  It has a LM317/LM337
pair, small heat sinks, regulator, bypass caps, rectifiers and filtering
caps all on one board for about $10 delivered.  To this you add a small
transformer and piggy-back a 7805T/heat sink and that would give the 3
voltages required by this unit.

Of course it's linear so it's got the linear heat dissipation issue but by
the right pick of transformer that could be as low as about 3W (around 2KWH
per month).  Then again, it's also got the linear noise "problems" which are
pretty much zero.

73/jeff/ac0c
www.ac0c.com
alpha-charlie-zero-charlie

-----Original Message-----
From: Bob kb8tq
Sent: Wednesday, August 31, 2016 7:49 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Anybody want a Thunderbolt power supply?

Hi

It is not that hard to do. Use a linear rather than a switching approach.
Run the +12 and +5 supplies off of LT1764 regulators. The -12 is very low
current, run it off of a low noise op amp. There are lots of toroidal line
transformers that will drive something like this.

Bob

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and follow the instructions there.

Someone could come out with a circuit board for a single configurable
voltage and decent noise specs. Use three of them for a Tbolt.

It is really easy to use the transformer from an old microwave oven to make
your own power transformer - the HV and the 110 volt windings are on
separate parts of the core so it is a matter of a few minutes to hacksaw off
the HV winding and you can use standard household THHN wire for your new
secondary - wind ten turns, measure the voltage and use that to figure how
many turns you actually needed.

If someone came out with such a bare board, I would buy 20 of them just to
keep around for projects.

Dave

Randall wrote:

For those who need an absolutely-no-soldering solution, there are any
number of good, triple-output linear lab/bench supplies.  My first
choice among these would be the Power Designs "TP" series -- TP325,
TP340, TP343 (and their "A" and "B" successors).  The HP 6236A (and B)
are also good candidates, although the +/-0-20v supplies are only good
for 500mA -- so the +12v supply to the Tbolt sits in 500mA current limit
for a short time while the Tbolt oven warms up from a cold start (not a
problem, just an irregularity).

Tested and guaranteed samples of all of these can be bought for $25-100
if you are patient (pay no attention to the loonies who list them for
$250-350).

Examples:
http://www.ebay.com/itm/172309780663
http://www.ebay.com/itm/142097506311
http://www.ebay.com/itm/172318644899

There are two potential disadvantages.  The first is size (particularly
WRT the Power Designs units -- the HPs are much smaller).  The second is
their adjustability.  You would not want to brush against one of the
voltage-setting knobs accidentally and send your Tbolt to GPS heaven.
The cure for this is a small dab of RTV on each knob.  Set the supplies
to the desired voltages, then apply a dab of RTV from the skirt of each
knob to the front panel of the supply.  Check the voltages while the RTV
is still workable, and adjust if necessary.  Let the RTV set, and it
would take some effort to change the voltages.

If your Tbolt came with a switching PS that you are replacing, you
probably already have a power cable that terminates in the proper Molex
connector to feed the Tbolt.  But what if you don't?  You will need to
build a power cable using the correct Molex connector shell (Molex p/n
50-57-9406) and contacts (Molex p/n 16-02-0103).  The contacts are made
to be crimped to the wires from the power supply.  The Molex crimp tool
(Molex p/n 63811-8700) is breathtakingly expensive (about $350).  Others
are less, including (I am told) a pretty cheap one from Radio Shack.

Best regards,

Charles

Post should have been:
Acts like noise current flowing in the voltage setting network (R || C).Flicker noise appears to kick in below 1Hz or so.
Bruce

On Thursday, 1 September 2016 8:23 PM, Bruce Griffiths <bruce.griffiths@xtra.co.nz> wrote:

Acts like current  noise flowing in the voltage sett

On Thursday, 1 September 2016 5:08 PM, Charles Steinmetz <csteinmetz@yandex.com> wrote:

Randall wrote:

For those who need an absolutely-no-soldering solution, there are any
number of good, triple-output linear lab/bench supplies.  My first
choice among these would be the Power Designs "TP" series -- TP325,
TP340, TP343 (and their "A" and "B" successors).  The HP 6236A (and B)
are also good candidates, although the +/-0-20v supplies are only good
for 500mA -- so the +12v supply to the Tbolt sits in 500mA current limit
for a short time while the Tbolt oven warms up from a cold start (not a
problem, just an irregularity).

Tested and guaranteed samples of all of these can be bought for $25-100
if you are patient (pay no attention to the loonies who list them for
$250-350).

Examples:
    http://www.ebay.com/itm/172309780663
    http://www.ebay.com/itm/142097506311
    http://www.ebay.com/itm/172318644899

There are two potential disadvantages.  The first is size (particularly
WRT the Power Designs units -- the HPs are much smaller).  The second is
their adjustability.  You would not want to brush against one of the
voltage-setting knobs accidentally and send your Tbolt to GPS heaven.
The cure for this is a small dab of RTV on each knob.  Set the supplies
to the desired voltages, then apply a dab of RTV from the skirt of each
knob to the front panel of the supply.  Check the voltages while the RTV
is still workable, and adjust if necessary.  Let the RTV set, and it
would take some effort to change the voltages.

If your Tbolt came with a switching PS that you are replacing, you
probably already have a power cable that terminates in the proper Molex
connector to feed the Tbolt.  But what if you don't?  You will need to
build a power cable using the correct Molex connector shell (Molex p/n
50-57-9406) and contacts (Molex p/n 16-02-0103).  The contacts are made
to be crimped to the wires from the power supply.  The Molex crimp tool
(Molex p/n 63811-8700) is breathtakingly expensive (about $350).  Others
are less, including (I am told) a pretty cheap one from Radio Shack.

Best regards,

Charles

time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Hi

The easy answer for a couple dozen Tbolts is a +15 V high current linear supply and a low power -15 V linear. Wire them to regulators mounted on chunks of perf board.

Bob