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PostPosted: 26 Feb 2017, 05:13 
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mwhouston wrote:
Well for me the trying is over. I'm now using double trannies and it is working well.


Hi,

Its possible to use inverters or SMPS but supplying the current is normally the problem.
Its OK on signal tubes but power tubes is a bit difficult. :)

I know the idea of loosing the mains transformer is alluring but its a dangerous place to be.
In theory you can transformer isolate the inputs and outputs but what's the point..because they would have to be isolation TX's voltage dependant insulation etc.

In industry the floating systems are fed with opto isolators and Fiber optics. (Don't go there).. :D

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M. Gregg

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PostPosted: 26 Feb 2017, 05:21 
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I actually thought of three different input trannies which would do the input isolation task. In fact I have all three of them. But all three had huge drawbacks. "Just bite the bullet Mark", so I did. Far better solution.

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PostPosted: 26 Feb 2017, 05:28 
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Yes,

Power isolation is much easier than trying to isolate/decouple inputs and outputs.
There is to much to go wrong and again fault current is not limited.

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M. Gregg

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PostPosted: 26 Feb 2017, 10:15 
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While not a universal supply, I did build these two units several years ago.

The first is a "Mains Breakout Box" which allows me access to mains voltage while prototyping.
Attachment:
Power_Adapter.jpg
This unit provides secure connections, switched operation, power on indication, and fuse protection.

The second unit is a "Universal Power Supply" rigged for use with a wide variety of octal rectifier tubes.
Attachment:
Flexible_PS.jpg
This unit takes a center taped transformer secondary and a filament supply and delivers a filtered DC output. It has a first capacitor of 30µf/500V and a filter consisting of an 8H/125mA choke and a 100µf/500v capacitor. It can handle any transformer up to 700 vct (350v-0-350v) and can deliver up to 125mA of current.

Using these two boxes I can quickly grab a power transformer and wire up a prototype power supply for any amp I may be prototyping. They have really come in handy on multiple occasions.


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PostPosted: 26 Feb 2017, 15:08 
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Suncalc wrote:
The first is a "Mains Breakout Box" which allows me access to mains voltage while prototyping.


Looks like my "Watt Box" for biasing some amps that require "Turn RV-x for x-watts mains draw" in their manuals :blush:

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