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 Post subject: 250 volt power supply info needed.
PostPosted: Jan Wed 09, 2019 6:31 pm 
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Location: Sheridan, Wyoming
I have looked for info on building a 240 volt, diode bridge rectified, CLC power supply out of my new EDCOR xpwr119-120 power transformer. The transformer is 120 volt, 60 hz primary, and the secondary is 240 volt@ 200 ma. , and has 12.6 volt, 3 amp filament winding. I need info on the microfarad rateing for my electrolytic capacitors and need to know if a choke of 30 H would be ok. I would like to know what value resistor would be best for the bleeder resistor. What I am asking is for someone to direct me to a site with an existing 240 or 250 volt power supply schematic is shown. I can just copy that schematic and use the values given there. Thanks.......William


Last edited by williampage on Apr Thu 04, 2019 10:58 pm, edited 1 time in total.

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 Post subject: Re: 250 volt power supply info needed.
PostPosted: Jan Wed 09, 2019 7:57 pm 
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Location: Minneapolis, MN USA
What will be load on the power supply and what are it's current requirements ?
What is the correct model number of the Stancor power transformer ?
30 H choke is HUGE.
Bleeder resistor is usually chosen to draw around 10 percent of current required by the load.


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 Post subject: Re: 250 volt power supply info needed.
PostPosted: Jan Wed 09, 2019 8:40 pm 
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there is this:
http://www.duncanamps.com/psud2/

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"Measure voltage, but THINK current." --anon.


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 Post subject: Re: 250 volt power supply info needed.
PostPosted: Jan Wed 09, 2019 8:41 pm 
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http://www.hammondmfg.com/pdf/5c007.pdf

How much DC current? What ripple can you tolerate?

A 240 VAC transformer might give you 240 Volts out (under load).

Rich


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 Post subject: Re: 250 volt power supply info needed.
PostPosted: Jan Wed 09, 2019 10:37 pm 
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Do you need the 240 VDC? That transformer is probably going to get you about 210-215 VDC under load with a full diode bridge, capacitor-choke-capacitor filter. What is your application?

Norm

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 Post subject: Re: 250 volt power supply info needed.
PostPosted: Jan Wed 09, 2019 11:56 pm 
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I was hoping to copy the AC regen receiver in back of the RCA tube manual. The schematic is on the site, "some regenerative receivers- W7EKB" The schematic is at the last receiver listed on line 5, and is simply called "regenerative shortwave receiver". The schematic is from an old RCA tube manual. By the way, can both of the air variable caps be substituted by a two gang cap? If you can get the tracking together, it looks ok to me. The tap on the secondary of the detector tube air variable cap should be no problem, I would think. I am adept at winding accurate coils. Any info appreciated. You see. I can learn more on this site in minutes than I can learn by looking through book after book after book! William


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 Post subject: Re: 250 volt power supply info needed.
PostPosted: Jan Thu 10, 2019 1:37 am 
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I think you would be okay with the lower voltage for the tube plates. R4 could be adjusted to get the voltage up to 100 VDC for the screen of the RF amp tube. It doesn't look like a ganged capacitor is going to work there. I don't see that it would track because T1 and T2 are completely different transformers. The circuit is from the 1937 RCA Tube Manual. Your power supply would be some 1N4007 diodes, two 80 MFd 450 VDC capacitors, a 5H choke, and maybe a 100K 2watt resistor across each capacitor as a bleeder.

Norm

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 Post subject: Re: 250 volt power supply info needed.
PostPosted: Jan Thu 10, 2019 5:47 pm 
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You probably have 30 years of experience here. What you have just told me would take me forever to figure out for myself. As for the 2 transformers. I always thought that if the secondary of the RF transformer was of the same number of turns as the primary of the detector coil, or maybe the detector coil would be 1 or 2 less turns than the secondary of the RF transformer, then it would work. You could just play around with the number of turns onto which you would place the tap on the secondary of the detector transformer, until you get it right. That was just my thinking there. I have a dual 140 pf air variable cap, which I wanted to use. I intended to wind my own coils anyhow! William


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 Post subject: Re: 250 volt power supply info needed.
PostPosted: Jan Thu 10, 2019 5:52 pm 
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williampage wrote:
You probably have 30 years of experience here. What you have just told me would take me forever to figure out for myself.


Ahh...but that is part of learning. Often it is better to be patient and start at the bottom, then you truly understand what you are doing.


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 Post subject: Re: 250 volt power supply info needed.
PostPosted: Jan Thu 10, 2019 6:04 pm 
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William,

Looking at it again, I think you are probably right. I was using the wrong information when I posted earlier. If the two transformers have the same secondary number of turns, they should track.

Norm

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 Post subject: Re: 250 volt power supply info needed.
PostPosted: Jan Thu 10, 2019 6:26 pm 
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Quote:
Looking at it again, I think you are probably right. I was using the wrong information when I posted earlier. If the two transformers have the same secondary number of turns, they should track.


True, if the stray capacitance/inductance from circuit layout is identical... this is why trimmer capacitors were invented!

Rich


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 Post subject: Re: 250 volt power supply info needed.
PostPosted: Jan Thu 10, 2019 6:50 pm 
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Norm. I looked at the tubes data sheets, and the most plate current for typical operation of any of the tubes, at 250 volts, was 9.2ma. So I guess that the 5 hy choke need not be any larger a MA rating than that of all 4 tubes{ about 35 MA for all of the tubes} and that a hammond 5 hy, 50 ma choke should be just fine.William


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 Post subject: Re: 250 volt power supply info needed.
PostPosted: Jan Thu 10, 2019 7:01 pm 
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If the total current is only 35mA, you don't need a choke at all....

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"Measure voltage, but THINK current." --anon.


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 Post subject: Re: 250 volt power supply info needed.
PostPosted: Jan Thu 10, 2019 7:05 pm 
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pixellany wrote:
If the total current is only 35mA, you don't need a choke at all....
But it hurts nothing to use one.

- Leigh

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 Post subject: Re: 250 volt power supply info needed.
PostPosted: Jan Thu 10, 2019 7:07 pm 
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Leigh wrote:
pixellany wrote:
If the total current is only 35mA, you don't need a choke at all....
But it hurts nothing to use one.

- Leigh

Of course!!----except in my case, i might object to the pain in my wallet....

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 Post subject: Re: 250 volt power supply info needed.
PostPosted: Apr Thu 04, 2019 1:47 am 
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I must have been half asleep. Why did I think he was asking about RF???? "Tracking" is usually RF.

Quote:
Quote:
Looking at it again, I think you are probably right. I was using the wrong information when I posted earlier. If the two transformers have the same secondary number of turns, they should track.


True, if the stray capacitance/inductance from circuit layout is identical... this is why trimmer capacitors were invented!

Rich


Sorry for my confusion!

Rcih


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 Post subject: Re: 250 volt power supply info needed.
PostPosted: Apr Mon 29, 2019 5:21 pm 
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Location: Lexington, KY USA
William,

Can you link some information for us on your power transformer?

How about the receiver you want to power? I suppose we might try to find it ourselves, but some of us are pretty lazy.

Are there other components you have on hand already that might be used for your project? The forum's advice might be tailored toward minimizing what else you would have to acquire.

For sure, don't go out and spend money on a power supply choke for a simple receiver project.

It's a little confusing mixing power supply and RF stage questions, but still better than starting multiple threads for the same project.

Getting multiple RF stages to track properly can be hard. Especially for multiple bands. Many 30s table radios with SW bands actually didn't bother with tracking the SW bands, and would work well only on the MW band. So you may want to keep separate tuning capacitors for each stage. However, if you only have multi-gang caps in your junkbox, no harm in leaving the extra gang unused.

Ted


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 Post subject: Re: 250 volt power supply info needed.
PostPosted: Apr Mon 29, 2019 5:46 pm 
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Is this the radio? (RC13, pg. 182)


Attachments:
RC13 4 Tube Regen.jpg
RC13 4 Tube Regen.jpg [ 140 KiB | Viewed 267 times ]
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