[time-nuts] Anybody want a Thunderbolt power supply?

Clint Jay cjaysharp at gmail.com
Wed Aug 31 08:59:39 EDT 2016

Ah,  these are the LM723 based linear supplies,  Lambda Coutant made
variants as did Farnell,  they're renowned as high reliability,  low noise

There are schematics out there for the variants but they're all extremely
similar if not identical.

I think I may even have a couple of original manuals with schematics,  I
may be able to dig them out and scan if they're of interest.

On 31 Aug 2016 13:01, "Jerry O. Stern" <jsternmd at att.net> wrote:

> Charles, do you have the schematic for the HTAA-16W-A  ?  The KO4BB mod
> has limited info
> Tnx
> Jerry
> K1jos at arrl.net
> -----Original Message-----
> From: time-nuts [mailto:time-nuts-bounces at febo.com] On Behalf Of Charles
> Steinmetz
> Sent: Wednesday, August 31, 2016 4:49 AM
> To: time-nuts at febo.com
> Subject: Re: [time-nuts] Anybody want a Thunderbolt power supply?
> Nick wrote:>
> > I’m going to shoot for <= 35 mV P-P. If you need better than that,
> > then it probably turns into a hybrid switching+linear system
> It's been years since I played with Tbolts (as opposed to just using
> them), but as I recall there was no possibility whatever of getting the
> best results from any switching supply without at least one stage of linear
> "polishing."  In fact, everything I tried with initial switching regulation
> benefitted from two levels of linear polishing.  It was my conclusion that
> starting with a switching supply of any sort is a bad idea.
> I found that for best performance the -12v supply, which feeds the DAC,
> needs to be about 1000 times better than what you are shooting for (i.e.,
> low tens of uVp-p).  That surprised me, because I assumed there must be
> some internal regulation of the DAC supplies -- but it was what my testing
> showed.
> Sure, a Tbolt will work with dirtier power than that, but for real
> time-nuts performance I consider an all-linear supply with an
> ultra-low-noise -12v rail to be absolutely necessary.  Since that is not
> very hard to provide, I see no reason to try to make do with less.
> One low-cost solution is to wait for a cheap Power One HTAA-16W-A
> triple-output power supply to show up on ebay, and do a very minor
> modification to raise the +12v current limit (so it will handle the first
> moments of a cold start without current limiting) as detailed here:
> <http://www.ko4bb.com/getsimple/index.php?id=download&file=06_Misc_Test_
> Equipment/Power_One/Power_One_HTAA-16W-A_mod_for_
> Thunderbolt_power_supply.pdf>
> That approach achieves excellent results -- close to the best you can do
> -- with very little fiddling.  If one wants the very best performance, the
> -12v supply can be adjusted down to -16v or so to provide the headroom to
> add a ULN regulator or a capacitance multiplier.  (The Tbolt only draws a
> few mA from the -12v supply, so the ULN regulator can be a suitable op amp
> with no external pass transistors.)
> Last time I bought them, I paid $25 for a lot of three HTAA-16W-A's.
> Best regards,
> Charles
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