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 Post subject: Need High Current B+ Power Supply
PostPosted: Sep Fri 27, 2019 1:48 am 
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Joined: Jan Mon 17, 2011 2:10 am
Posts: 223
Location: Revere,Massachusetts U.S.A.
Hi Forum, I've built a number of radio receivers - preamps, and amplifiers, now I need to be able to supply enough B+ (Current) for all the breadboards. Any ideas from the forum on which circuit would do the trick ??

The B+ VDC is from 90 to 165

Thank You, Tony

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 Post subject: Re: Need High Current B+ Power Supply
PostPosted: Sep Fri 27, 2019 2:11 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 2332
Location: Saskatoon
We would need to know how much current. To get a reasonable estimate, you could add up the plate current of all the tubes you intend to power from this supply. If you don't know the actual plate current, then use the typical plate current ratings from the tube data sheets.


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 Post subject: Re: Need High Current B+ Power Supply
PostPosted: Sep Fri 27, 2019 4:50 am 
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Joined: Mar Thu 21, 2019 3:53 pm
Posts: 150
The most simple form of variable voltage power supply is a normal power supply (transformer, rectifier, CLC filter) with a variac in front to adjust the output voltage. The VA rating of the variac and power transformer will depend on the current demand. The heaters would be supplied by a separated transformer connected directly to the mains supply.
I have one of this adjustable type of PSU which can deliver 0-500V up to 125mA and 6.3V at fixed level.


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 Post subject: Re: Need High Current B+ Power Supply
PostPosted: Sep Fri 27, 2019 3:17 pm 
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See this from member Leigh
http://www.atwaterkent.info/Images/LR8N3RFh.gif

Attachment:
LR8N3RFh.gif
LR8N3RFh.gif [ 81.53 KiB | Viewed 1354 times ]


edit: added pic

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Last edited by Phil Coe on Sep Sat 28, 2019 1:56 am, edited 2 times in total.

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 Post subject: Re: Need High Current B+ Power Supply
PostPosted: Sep Fri 27, 2019 3:46 pm 
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Joined: Jul Mon 26, 2010 8:30 pm
Posts: 28607
Location: Annapolis, MD
To me, this is a task for an old power transformer pulled out of the junk pile. Add some 1n4007 diodes and some electrolytics and you have a power supply. (Run it with a Variac to control the voltage)
Beware of using Variac directly---you will not be isolated from the AC line.

OR---get a lab supply.

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 Post subject: Re: Need High Current B+ Power Supply
PostPosted: Sep Fri 27, 2019 11:20 pm 
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Joined: Sep Wed 10, 2014 2:01 am
Posts: 2169
Location: Costa Mesa, California
Electrophoresis power supplies from EBay are pretty cheap and work great. I use a Bio-rad supply for my projects. You would need to make your own filament supply. I use an old Tektronix scope transformer that has a lot of windings including multiple separate filament windings. EBay sellers usually have a list of the windings and the data sheets are out there. These could also be used for a power source, however I don’t use mine that way. I mounted my Tektronix transformer in a chassis with multiple bananna jacks and a jumper so I can use sets of jacks in series for 12.6 vac.

Norm

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 Post subject: Re: Need High Current B+ Power Supply
PostPosted: Sep Sat 28, 2019 1:21 am 
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Joined: Sep Tue 30, 2014 6:08 am
Posts: 5680
Location: Norfolk, VA
Phil Coe wrote:


Also using the LR8:

https://www.nutsvolts.com/questions-and ... wer-supply

Attachment:
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QA_0606_Byers_150V.jpg [ 46.43 KiB | Viewed 1362 times ]

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 Post subject: Re: Need High Current B+ Power Supply
PostPosted: Sep Mon 30, 2019 4:07 pm 
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Joined: Jan Tue 16, 2007 7:02 am
Posts: 3767
Location: Lexington, KY USA
Note that the regulated supplies shown above lack any formal current limiting to protect the power transistor. One slip on your breadboard and it's done.

Usually the accurate regulation is not needed anyway, so the above suggestions for a few diodes and filter capacitors can work pretty well. I might add that you want a bleeder resistor on the DC output to help the low-load regulation, as well as discharge the caps when the supply is off. A higher power and lower resistance bleeder is a good idea for this service.

Most of us have junkboxes with stuff to use for the expensive parts, if we dig long enough. You might tell us what you have on hand.

If you already have a variac and isolation transformer on your bench, a rectifier - filter - meter module can be used with that to make a B+ supply. For safety, a special connector might be used for the AC input to the module, so it can't be plugged into the wall outlet by accident.

Ted


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