kevin gilmore

goldenreference low voltage power supply

343 posts in this topic

I'm happy to report that the goldenreference low voltage dual

power supply works as designed, and tests less than 1 microvolt

of noise. Going to have to take it to work and put it in a screen

room to really measure the noise.

 

http://gilmore.chem.northwestern.edu/goldenreferencedual.jpg

 

however there is one silkscreen error seen by the extra + near the

47uf cap on the right side. I will update the files shortly.

 

All 4 of the 47uf caps need to have their plus sides pointing to the left.

 

very happy with this

Edited by kevin gilmore

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thanks for doing this as always, definitely putting these into the preamp

 

between this and the SiC psu's the lt1021 purchases are going to break the bank

 

How much current are those mjw21194 good for without heatsinking? I'm looking up some of the to247 sheets but I don't see the relevant numbers

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my unreg primary is 41v, so its way higher than normal.

 

I did attach the biggest  U bracket heatsinks I had around

(bhse ones)

 

Ran 500ma load.

 

Definitely gets too hot to touch in a few minutes.

 

you do realize this is set for +/-20, so if you want other

voltages you have to change the feedback resistors.

 

(+/-20 is my favorite voltage for ssdynalobal)

Edited by kevin gilmore

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sure I'll keep it in mind, my first board is going into the dynalo2. I was assuming 20 would also work for the nfb preamp

 

do you need such high voltage ratings for the ksp* parts? putting in a digikey order now to group stuff with the lt1021

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you can with parts changes including higher voltage rating caps, and opa445's

take the output voltage all the way up to +/-60V

in which case you need the ratings on those transistors.

compared to everything else, the transistors are among the cheapest of the parts.

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How much drop voltage does the LV GR need to operate?

Sent from my iPad using Tapatalk HD

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likely depends on current level, have to bolt to heatsink to test.

at 500ma output, looks like about 4V

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I was unsuccessful in searching for the schematic.

Which are the feedback resistors that set the output?

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its a 10 volt reference, the feedback resistors are 1.5k which is a divide by 2.

So if you change the top 1.5k resistor you can get any voltage you want.

750 ohms makes it 15v

 

http://gilmore.chem.northwestern.edu/goldenreference.pdf

 

change R8,R9

Edited by kevin gilmore
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Thanks Kevin.

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Awesome!

Ive got all the parts on the way (“all”).

Im using 2 25va antek transformers for this psu, so everything including ssdynalo should fit in a 1U rackmount case.

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2 watt transformer... no

22 watt, just barely

30 watt transformer is about right

one of the mounting holes is 25th off of square.

current posted boards (dual and singles) have the mounting

holes one size smaller, the silk screen fixed, and 1 resistor

each moved by 25th.

done

measurements this morning in a screen room is about 800picovolts

of noise. and voltage stability exceeding 6.5 digit meter.

anything better is going to require stupidly expensive test gear.

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The schematic seems to be missing the ground output, which I assume is straight line down the middle. ::)

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ground down the middle.

there is actually a benefit of dual supplies. the noise spikes what little of them exist

cancel.

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what's the unpopulated 10 ohm spot for?

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what's the unpopulated 10 ohm spot for?

it's an error, not connected to anything.

Got mine done and running.

A few things missed in BOM:

512-KSP42TA    4
512-KSP92BU   4
512-1N914         4
821-1N4007       2

 

eUoj792.jpg

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what's the unpopulated 10 ohm spot for?

 

I asked Kevin the same question when inspecting the board. Here is Kevin's response: 

 

"the 10 ohm thing is the krell way of earth ground to power supply ground.

 

very few if any will ever use it. but its there just in case."

 

 

Nice build IKong. 

 

What voltage and current do you have running with the PS and what's the temperature of the MJW21193?

Edited by mwl168

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there is actually a benefit of dual supplies. the noise spikes what little of them exist

cancel.

does that apply to the dual made of two singles in series, or only to the dual made of complementary parts?

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what's the unpopulated 10 ohm spot for?

 

not an error.  from the krell power supply, 10 ohm resistors from iec input ground to power suppy ground.

 

not likely that anyone including me is going to use it though.

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does that apply to the dual made of two singles in series, or only to the dual made of complementary parts?

 

if you do the 2 complementary singles, then yes, otherwise no.

 

also the bom lists the on board pass transistors, not the off board ones

 

I did more testing, and at 500ma, the minimum dropout voltage seems

to be closer to 3v.  But at 5v, the pass transistors do just fine with a small

heatsink as is.

 

5V, 500ma ...  2.5 watts

Edited by kevin gilmore

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So this is the best PS board to date for the Dynalo?  >elpac(obviously) the original?  sigma22? GS-X mk2 psu? :)

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yes, buy a bunch.

but it is more money than an open frame ps.

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Kevin Gilmore said, "yes, buy a bunch."

 

I assume you meant:  yes, BY a bunch, i.e. a lot better. :laugh:    On the other hand maybe you did mean BUY a bunch. :dance:  Oh well. ;D

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ground down the middle.

there is actually a benefit of dual supplies. the noise spikes what little of them exist

cancel.

Can you provide a bit more information on those noise spikes you see?

 

Also

 

 

measurements this morning in a screen room is about 800picovolts

of noise. and voltage stability exceeding 6.5 digit meter.

under which circumstances, bandwidth and current pulled for instance ?

Can you provide some comparison to the standard LV 78/7915 type supply?

 

 

To sum up:

- the GR LV can regulate at 3V but would be better at 4-5V,? and can be used up to 60V depending on components used?

- the GR HV can regulate at 8V?

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the noise spikes are 120hz (100hz for you) and due completely to the switching noise
of the input diodes. every power supply, even tube rectified ones do this. The idea
is to remove the spike noise, and its not easy. caps across the diodes, etc, just does not
work.

and by the way, so far, I can't even get close to these numbers with a shunt regulated
supply, the noise rips right thru the main current source.

7815 is rated at 90 microvolts of noise (ti datasheet). which is great except that in the typical configuration
the diode noise rips right thru, and is usually in the millivolt range. and the voltage stability
is +/-4% over commercial temperature range. plus line and load regulation.

S22, same thing, the capacitance multiplier at the input is useless. Some companies in
the stupidly overpriced 3 terminal replacement business call this a gyrator. Nope, not a gyrator.

yes it can regulate at 3V, but you don't want to do that. What you might want to do is use
that voltage to calculate line voltage -15% for the absolute minimum voltage. Then make
sure all the components are rated for line voltage +15%

its all about heat in the pass transistors.

if you want to go down to 8 volts, you have to change the series zener to 4.7v
that zener is there to make sure the thing starts up under load.
and change the reference to 5v

 

here is the original design that was modified by ucc, then modified by me.

http://waltjung.org/PDFs/Improved_PN_Regs.pdf

Edited by kevin gilmore
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