[ARC5] 28VDC Regulator

[J Mcvey]

 There is also this kind of DC-DC bucking that that can used on the output side.However this one also has the 40V limit and may need to be "RF quieted" with filtering on the I/O.There are probably others with higher input tolerance,
www.ebay.com/itm/Adjustable-DC-DC-LM-2596-Converter-Buck-Step-Down-Regulator-Power-Module-LW-SZUS/232372936877?epid=2273974522&hash=item361a81a0ad:g:FFoAAOxy3yNTeq8J:sc:USPSFirstClass!12589!US!-1


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Adjustable DC-DC LM 2596 Converter Buck Step Down Regulator Power Module...

LM2596 Step-down Power Module x1. How to adjust the accuracy?. 4、Output power: 75W Max. | eBay!
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    On Sunday, July 1, 2018, 9:52:45 PM EDT, Rich Post <kb8tad at gmail.com> wrote:  
 
 Wayne,
Does the transformer have other secondaries?  Most of the older solid state receiver transformers have a 12-15 volt source also.  If so, hook that in series with the primary, or hook it up as a bucking source to the primary.  
I have also rescued a few such transformers, including one that had enough secondaries which when hooked in series made a useful isolation transformer.   And yes, several 2N3055 pass transistors with bases fed by a low current regulator source make that a nice regulated PS.   I have also recycled the output transistors for pass regulation as well as the heat sink, assuming you have discrete transistors for output as opposed to a large IC.

Rich KB8TAD


On Sun, Jul 1, 2018 at 6:43 PM, Robert Eleazer <releazer at earthlink.net> wrote:

Today I found a Toshiba AM/FM stereo receiver someone had thrown out.  It was dead but yielded a  nice big heavy transformer that has a number of outputs, including one with 64VCT.  I still would like to build a dedicated 27.5VDC power supply that could run my ARC-114 and ARC-116.  They run fine on my variable bench power supply.  I have found the LM317 and related series to be inadequate due to its input voltage limitation. I looked at the  LM338 specs and it does not refer to an input voltage limitation, although max output is 32VDC and output versus input cannot be greater than 40VDC. That 64VCT transformer will give me about 45VDC cap filtered input to the regulator. So, do y'all think the LM338K will do the job? Needless to say I would rather stay linear and not use a switcher. Thanks WayneWB5WSV      

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