Cgs synth

> Date: Fri, 19 Nov 2004 09:51:49 -0000
> From: "allanjhall" <allanjhall@...>
> Subject: Re: +/- 15V PSU questions
>
>
> Many thanks for the help Ken, it all makes much more sense to me
> now :-)
>
> I think I'll try it with 15-0-15 and check voltage across caps with
> scope and fit a 18-0-18 transformer if its looking too marginal
> under load - I'm trying to keep the heat from the heatsinks as low
> as possible as they will be in the same cabinets as VCO's and I
> don't want to warm them up too much. I'll use schotty diodes, but
> can't find low drop regulators for negative voltages, only positive
> ones such as LM2940 - looks like the cap requirements are a bit
> different too, LM2940 needs a medium size electro cap on the output
> rail, so I think I'll have to stick with 7815 and 7915's, or is it
> possible use low drop regulator on + rail only?
>
> BTW Is low dropout the same thing as low drop with regulators? I've
> had a look at datasheets but they assume you know what low dropout
> is!
>
> cheers,
> Allan
>
> --- In cgs_synth@yahoogroups.com, sasami@h... wrote:
>>
>>
>>> I'm going to be using the +/-15v psu's to supply some of the
> digital
>>> modules in my system to keep noise away from analog module power
>>> rails. Is there any reason why I couldn't attach the regulators
> to
>>> the pcb with short (50 to 100mm) flying leads so that they could
> be
>>> remotely mounted on a single large heatsink, with insulation
> washer
>>> kits to keep them electrically isolated from each other. I'd
> guess
>>> that they could be good for 600 to 800ma per rail in this
>>> configuration.....
>>
>> You need to keep the 100n capacitors physically close to the
> regulator, so
>> if you remote mount them, solder the 100ns directly to their pins.
>>
>>> Also, could you explain more fully why I would need to go up from
>>> 15v-0-15v to 18v-0-18v transformer for higher current outputs? I
>>> thought that with full wave rectification you get a higher DC
>>> voltage than AC anyway - somewhere near 1.3 to 1.6 times higher?
>>
>> square root of 2 is the figure. The problem is you lose a lot of
> voltage in
>> the process - 1.2 across the diodes and another 3 across the
> regulator. Also
>> the output from the capacitor is not a straight line. The higher
> the load,
>> the more it droops between cycles. The BOTTOM of this droop must
> be higher
>> than 18V for the regulators to work propperly.
>>
>> Also, the no-load output of the transformer is irrelevant (apart
> from
>> determining the minimum voltage for the electros), as you won't be
> running
>> no-load.
>>
>> If you really wanted to, the use of low-drop voltage regulators
> and schottky
>> diodes would save you a couple of volts of losses, allowing a
> greater load
>> to be taken from a 15-0-15 transformer.
>>
>> Ken
>>
> _____________________________________________________________________
> __
>> Ken Stone sasami@h... or sasami@c...
>> Modular Synth PCBs for sale
> <http://www.blaze.net.au/~sasami/synth/>
>> Australian Miniature Horses & Ponies
> <http://www.blaze.net.au/~sasami/>
>
>
>
>
>
> _______________________________________________________________________
> _
> _______________________________________________________________________
> _
>
>
> See the following URLS for the CGS Modular Synth home page:
> Main: http://www.cgs.synth.net/
> Secondary: http://otherunicorn.0catch.com/synth/
> -----------------------------------------------------------------------
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>

>So how did it work out ? Last time I built a + - 15 psu I used a 36v
>center tap xfrmr and an LM 723. I'd be interested in a cheaper
>solution. Everything else I tried was anemic, broadcasted, spikey, got
>hot fast... basically crap.
>
>G wong
>
>
>
>
>

> The Power-One HAA15-0.8-A, which provides + and - 15V at 800ma and

> the guts of the Synth Tech MOTM-900 supply, is available for $45

> Digi-Key. How much more costly is that than what you are

> Maybe the Power-One supplies cost more outside the US?
>
> -Richard Brewster
>
> jgwong wrote:
>
> >So how did it work out ? Last time I built a + - 15 psu I used a

> >center tap xfrmr and an LM 723. I'd be interested in a cheaper
> >solution. Everything else I tried was anemic, broadcasted,

> >hot fast... basically crap.
> >
> >G wong
> >
> >
> >
> >
> >

--- In cgs_synth@yahoogroups.com, sasami@h... wrote:
>
> >BTW, If you're outside of the US NEVER buy from Allied. I
thought
> >this shipping charge was large because of the weight of the
Power
> >One PSU's, so last month I foolishly ordered some Vactrols
and 20 of
> >8 pin IC's that would fit into a jiffy bag and Mouser would
charge
> >$12 by USPS small packet. They came in a big box (!) and
Allied
> >charged me $89 shipping, despite me requesting that items
be shipped
> >by USPS small packet service. I'm now the proud owner of
some of the
> >most expensive Vactrols in the Universe :-(
>
> I've heard this story before, so you aren't the first person they've
done it
> to. Bad news.
>
> Ken
>
__________________________________________________
_____________________
> Ken Stone sasami@h... or sasami@c...
> Modular Synth PCBs for sale
<http://www.blaze.net.au/~sasami/synth/>
> Australian Miniature Horses & Ponies
<http://www.blaze.net.au/~sasami/>

>
> If I may high-jack this thread briefly, it is on the subject of
> Power-One PSUs. I've just built a 6U case, incorporating a

> output (HCC-15-3) unit. The case has a single distribution
> board (for now) with power going in centrally (to combat line
> overload) and the + and - lines use two tracks anyway. There

> 9 sockets on this board (of which I'm using 5).
>
>
> I have jumpered pegs 2 and 3 and applied AC (via a switch

> fuse) to pegs 1 and 4, with 5 being left alone as per the
> instructions. I have wired the + out and - out pegs from the

> (there are several others to choose from i.e. S+ and S-, and in
> the centre, S+, S- and Com) to the + and - lines on the dist
> board, respectively. The 0V line I have attached to the frame,

> from there to the Earth point of the power cable.
>
> I appear to be having trouble with the earth. The case

> up, but it doesn't run the modules properly. I've checked the
> outputs, and I'm getting 24V across the + and - terminals, but
> when I check +12V to Earth or -12V to Earth I get a reading of 0
> and -0 respectively.
>
> I've checked the continuity from the IDC sockets through to the
> earth pin of the plug and there is good continuity. Similarly,

> is good comtimuity for each of the power rails back to the PSU.
> The IDC sockets are sound with no shorts, and the board is
> correctly isolated from the case. All the mains wiring and the
> wiring from PSU to dist board is from mains flex rated at well
> above the 3.4A maximum.
>
> I suspect I've misunderstood something rather than there

> a physical problem with the wiring.
>
> Your assistance would be greatly appreciated.
>
>
> --- In cgs_synth@yahoogroups.com, sasami@h... wrote:
> >
> > >BTW, If you're outside of the US NEVER buy from Allied. I
> thought
> > >this shipping charge was large because of the weight of the
> Power
> > >One PSU's, so last month I foolishly ordered some Vactrols
> and 20 of
> > >8 pin IC's that would fit into a jiffy bag and Mouser would
> charge
> > >$12 by USPS small packet. They came in a big box (!) and
> Allied
> > >charged me $89 shipping, despite me requesting that

> be shipped
> > >by USPS small packet service. I'm now the proud owner of
> some of the
> > >most expensive Vactrols in the Universe :-(
> >
> > I've heard this story before, so you aren't the first person

> done it
> > to. Bad news.
> >
> > Ken
> >
>

> _____________________
> > Ken Stone sasami@h... or sasami@c...
> > Modular Synth PCBs for sale
> <http://www.blaze.net.au/~sasami/synth/>
> > Australian Miniature Horses & Ponies
> <http://www.blaze.net.au/~sasami/>

>
>
>If I may high-jack this thread briefly, it is on the subject of
>Power-One PSUs. I've just built a 6U case, incorporating a dual
>output (HCC-15-3) unit. The case has a single distribution
>board (for now) with power going in centrally (to combat line
>overload) and the + and - lines use two tracks anyway. There are
>9 sockets on this board (of which I'm using 5).
>
>
>I have jumpered pegs 2 and 3 and applied AC (via a switch and
>fuse) to pegs 1 and 4, with 5 being left alone as per the
>instructions. I have wired the + out and - out pegs from the PSU
>(there are several others to choose from i.e. S+ and S-, and in
>the centre, S+, S- and Com) to the + and - lines on the dist
>board, respectively. The 0V line I have attached to the frame, and
>from there to the Earth point of the power cable.
>
> I appear to be having trouble with the earth. The case powers
>up, but it doesn't run the modules properly. I've checked the
>outputs, and I'm getting 24V across the + and - terminals, but
>when I check +12V to Earth or -12V to Earth I get a reading of 0
>and -0 respectively.
>
> I've checked the continuity from the IDC sockets through to the
>earth pin of the plug and there is good continuity. Similarly, there
>is good comtimuity for each of the power rails back to the PSU.
>The IDC sockets are sound with no shorts, and the board is
>correctly isolated from the case. All the mains wiring and the
>wiring from PSU to dist board is from mains flex rated at well
>above the 3.4A maximum.
>
> I suspect I've misunderstood something rather than there being
>a physical problem with the wiring.
>
>Your assistance would be greatly appreciated.
>
>
>--- In cgs_synth@yahoogroups.com, sasami@h... wrote:
>>
>> >BTW, If you're outside of the US NEVER buy from Allied. I
>thought
>> >this shipping charge was large because of the weight of the
>Power
>> >One PSU's, so last month I foolishly ordered some Vactrols
>and 20 of
>> >8 pin IC's that would fit into a jiffy bag and Mouser would
>charge
>> >$12 by USPS small packet. They came in a big box (!) and
>Allied
>> >charged me $89 shipping, despite me requesting that items
>be shipped
>> >by USPS small packet service. I'm now the proud owner of
>some of the
>> >most expensive Vactrols in the Universe :-(
>>
>> I've heard this story before, so you aren't the first person they've
>done it
>> to. Bad news.
>>
>> Ken
>>
>__________________________________________________
>_____________________
>> Ken Stone sasami@h... or sasami@c...
>> Modular Synth PCBs for sale
><http://www.blaze.net.au/~sasami/synth/>
>> Australian Miniature Horses & Ponies
><http://www.blaze.net.au/~sasami/>
>
>
>
>
>
>
>See the following URLS for the CGS Modular Synth home page:
>Main: http://www.cgs.synth.net/
>Secondary: http://otherunicorn.0catch.com/synth/
>Yahoo! Groups Links
>
>
>
>
>
>
>
>