two switcher circuits

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https://www.dropbox.com/s/keynlhs9ktzivyh/LTM8078_dual_neg_1.asc?dl=0

https://www.dropbox.com/s/htzvrbnd8qx3ooi/LTM8078_plus_minus_1.asc?dl=0







--  

John Larkin         Highland Technology, Inc

Science teaches us to doubt.

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Re: two switcher circuits
On 2020-04-03 10:34, snipped-for-privacy@highlandsniptechnology.com wrote:
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Cute.  Sure is going to need some input filtering though!

Cheers

Phil Hobbs

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Dr Philip C D Hobbs
Principal Consultant
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Re: two switcher circuits
On Fri, 3 Apr 2020 11:09:33 -0400, Phil Hobbs

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I have to resist the temptation to put bypass caps across voltage
sources in Spice. The LTM8078 apparently has inductors but no caps.
Even that is impressive. Can anybody x-ray one for me?

https://www.dropbox.com/s/b6dogwrwioka5nj/LTMs_Top.jpg?raw=1

https://www.dropbox.com/s/m1u04ne0w575ykl/LTMs_Bot.jpg?raw=1





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John Larkin         Highland Technology, Inc

Science teaches us to doubt.

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Re: two switcher circuits
On 4/3/2020 10:34 AM, snipped-for-privacy@highlandsniptechnology.com wrote:
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Not a switcher, but expedient:

<https://www.dropbox.com/s/uf29ubm0v1ox7pv/linear_tracking.PNG?dl=0



Re: two switcher circuits

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Driving the adj pin of a 3t regulator is an under-appreciated trick.
They are nice, cheap, thermally limited power amps.

We have standardized on 24 volt warts for small boxes, so we want to
switch mostly. So multiple outputs from tiny switchers is good.

Just minutes ago I got this:

https://www.dropbox.com/s/wxerjg36c3ow8s5/J744_3.jpg?dl=0

https://www.dropbox.com/s/lnn1jwk7gm1h713/J744_2.jpg?dl=0

The idea is to get away from the boring Hammond boxes. This is a
semi-custom extrusion with nice grounding and thermals. We plan to
laser blast the anodize for external artwork.






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John Larkin         Highland Technology, Inc
picosecond timing   precision measurement  

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Re: two switcher circuits
On Fri, 03 Apr 2020 11:48:20 -0700, John Larkin wrote:

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dl=0
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Who made those boxes for you?  I have an upcoming project where I
need something similar.

--  
Chisolm
Texas-American


Re: two switcher circuits
On Fri, 03 Apr 2020 14:10:06 -0500, Joe Chisolm

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https://www.pumay-aluminum.com/products/

They cut one of their extrusions to length and machined it per our
drawing. The blue anodize color is a little garish, so we'll ask them
to tone it down a bit next time.

The holes are drilled/tapped after anodize, so are conductive and
don't have the problems that the self-tappers do on the Hammond boxes.
Like metal shavings everywhere and stripped screws.

We add a couple of metal bars inside that the board bolts to.

https://www.dropbox.com/s/1fglmrtg3l9pkf8/J002_1.jpg?raw=1


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John Larkin         Highland Technology, Inc
picosecond timing   precision measurement  

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Re: two switcher circuits
On 4/4/20 7:23 am, John Larkin wrote:
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Very nice.


Never ever use self-tappers. They work loose with vibration, and cut new  
paths when you re-insert them. You don't even need to tap if you use  
trilobular (thread-forming) screws. Taptite is one brand, but it's a DIN  
standard.

CH

Re: two switcher circuits
wrote:

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People extrude 3/4 holes in things like this, and then use
self-tapping screws. The partial holes tend to break taps.  




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John Larkin         Highland Technology, Inc

Science teaches us to doubt.

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Re: two switcher circuits
On 4/4/20 3:16 pm, snipped-for-privacy@highlandsniptechnology.com wrote:
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People don't make things to be serviced. Self-tappers can be ok in the  
absence of vibration or the need to service.

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Tapping deep holes in Al is fraught - the correct technique involves  
lots of reversals, and in large sizes, multiple passes with different  
taps, so it's slow.

CH

Re: two switcher circuits
wrote:

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Use a forming tap, versus a cutting tap.  Forming taps are very
strong, rarely break, and work very well in aluminum.  Use a tapping
lubricant intended for the purpose.

.<https://www.mscdirect.com/basicsof/thread-forming-taps

Joe Gwinn

Re: two switcher circuits
On 4/3/2020 2:48 PM, John Larkin wrote:
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I noticed that the LM317 is OK with its input sitting about 4-5" from  
the +/-50 switcher output filter caps, but without some extra filtering  
closer to the regulator the LM337 is unhappy about it and starts  
oscillating at low frequency

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Hammond makes some nice transformers at reasonable prices for e.g.  
vacuum tube amps but their enclosures sure are drab!


Re: two switcher circuits
On 2020-04-03 17:16, bitrex wrote:
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The 337's pass transistor is an NPN, so its output is via the collector,  
much like modern LDOs.  It's a perfectly good part when used as  
directed, but far less forgiving than the emitter-follower 317.

And tsk tsk on using those parts from a 50V supply--or are you using the  
HV variants?  (IDK if there's any difference apart from testing, of course.)

Cheers

Phil Hobbs

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Dr Philip C D Hobbs
Principal Consultant
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Re: two switcher circuits
On 4/3/2020 6:16 PM, Phil Hobbs wrote:
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The input-output voltage differential on the top and bottom 317 and 337  
exceeds the 40V limit for about 200 microseconds on startup with the  
+/-50 rails coming up in the sim way faster than they actually would  
IRL. I think it'll be okay. It's not going into production it's a  
place-holder to test the main board until I can get around to buying or  
building a PS that doesn't consume so much power for the client

Re: two switcher circuits
On 4/3/2020 8:47 PM, bitrex wrote:
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Shipments are suffering delays to my location and my girlfriend is in  
our home in another state (RI) that's banned non-essential cross-border  
traffic, I'm not a RI resident, and they're busting and fining people  
they seem to be serious about it. let the Constitutional scholars fight  
over it later.

some of my gear is stuck there, while I'm working on caring for an  
elderly parent up here at home in MA, no way she's staying some other  
place right now.

Doing some under-the-gun engineering here lol

Re: two switcher circuits
On 2020-04-03 14:48, John Larkin wrote:
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My eyes! My eyes!
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Yeah, it would be good to get them to tone it down a bit. ;)

Cheers

Phil Hobbs


--  
Dr Philip C D Hobbs
Principal Consultant
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Re: two switcher circuits
On Friday, April 3, 2020 at 5:55:02 PM UTC-4, Phil Hobbs wrote:
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What part number is this?  What color specification?  

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  Rick C.

  - Get 1,000 miles of free Supercharging
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Re: two switcher circuits
On Fri, 3 Apr 2020 17:54:54 -0400, Phil Hobbs

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Get serious, I'm only running 2 mA in that LED. We were wondering how
it would look, just the led on the PCB and a hole drilled into the end
plate. The light bounces around in the hole and it actually looks
pretty good from all angles. Don't need no light pipe.

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I kinda like it, but some other people here don't. The Chinese seem to
like bright primary colors, and it generally looks good on them.

We're investigating getting a 20-watt n/c fiber laser to blast the
lettering in-house.

--  

John Larkin         Highland Technology, Inc
picosecond timing   precision measurement  

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Re: two switcher circuits
On 2020-04-03 18:23, John Larkin wrote:
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It's the case I'm referring to. I might have a low threshold, but  
electric blue anodize screams "aliexpress" to me.  Of course, we're  
still using the black Hammond boxes round here, so perhaps it's my inner  
Amishman talking. ;)

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Fun.

Cheers

Phil Hobbs


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Dr Philip C D Hobbs
Principal Consultant
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Re: two switcher circuits
On Fri, 3 Apr 2020 18:39:51 -0400, Phil Hobbs

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Oh, I knew that.

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We found the Hammonds to be mechanically messy too. They don't always
saw the ends off the extrusions at a 90 degree angle.

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John Larkin         Highland Technology, Inc
picosecond timing   precision measurement  

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