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Old 4th February 2013, 10:59 AM   #271
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Quote:
Originally Posted by bcmbob View Post
. . .something for center tapped transformers only?
I think that I found out where the 100n came from.
On a center tap CRC power supply, the smoothing section at the bridge rectifier has its own ground. . . and then effectively a heavy duty jumper. . . to the reservoir/tank section that has a massive star ground. . . and then another heavy duty jumper. . . to the output jack. Aha! That last bit could have some little 100n caps or something at the output jack.

Well, the main point of this post is showing that a Center Tap specific CRC power supply has a different and somewhat more complex grounding scheme. Suitability for multi-parallel little caps power supply was limited, but I think I've managed to draw it.
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File Type: gif CT-CRC-5track.gif (38.7 KB, 196 views)
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Last edited by danielwritesbac; 4th February 2013 at 11:03 AM.
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Old 4th February 2013, 01:44 PM   #272
bcmbob is offline bcmbob  United States
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Looks like the PS boards I have been using will accommodate both styles of transformers. They have the small caps installed but work just fine with duals I have.

Since we didn't have "show and tell" when I was in school I'll try to make up for lost time here This is a little mock-up for final approval. Of course I'll use bigger wire (or copper strips if advised so) for the final construction. I have never done a DIY etched PCB so that might be another new adventure.
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File Type: jpg 20130204_073504.jpg (78.4 KB, 188 views)
File Type: jpg 20130204_090057.jpg (395.5 KB, 168 views)
File Type: jpg 20130204_091036.jpg (75.2 KB, 154 views)
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Old 4th February 2013, 02:22 PM   #273
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Right side picture, you have a dual secondaries transformer and it can perform more strongly when given specific support. That's good news.

You have two secondary windings--use ohmmeter to identify secondary#1 and secondary#2. And separate the output cable of your transformer so that you have a twisted pair of conductors for secondary#1 and a separate pair of twisted conductors for secondary#2.

Middle picture, don't attach any cable from a dual secondaries transformer to any part of the DC rails. All AC must go through the diodes (per every dual secondaries type schematic). See attachment.
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File Type: jpg dualbridgerectifier.jpg (146.1 KB, 147 views)
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Old 4th February 2013, 02:29 PM   #274
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Yeah, with dual secondaries, you might as well use two rectifier bridges. Otherwise, as with a center tap and one bridge, you don't fully-utilize the transformer.
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Old 4th February 2013, 02:40 PM   #275
bcmbob is offline bcmbob  United States
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O.K. I'll do another this afternoon.
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Old 4th February 2013, 04:06 PM   #276
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Center tap vs dual secondaries? The deal is that those two styles are competitors, like Windows VS Mac.

Without hindering bass/dynamics from dual secondaries transformers and without setting center tap transformers ablaze, a solution with neither problem has both hookups. I've never seen one because it would make more sense to put the bridge rectifier(s) on "daughtercards" and plug in whichever you needed.

However. . . Like a Jeep or Scout than can do either car or truck, here (attached) is a hermaphroditic power supply board that can use either a center tap or a dual secondaries transformer, properly. Proposed use: A "Tester" power supply for bench use.
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Old 4th February 2013, 07:06 PM   #277
bcmbob is offline bcmbob  United States
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Hey Daniel,

It's a good thing I don't embarrass easily. Here is the latest. Am I getting close?

Again, some of my confusion comes from my existing board . It is using the "3 point" configuration with dual secondaries. I believe you are saying that will work but is not optimal for this particular application. Is that correct?
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File Type: jpg Dual.jpg (671.1 KB, 70 views)
File Type: jpg 20130204_145057.jpg (79.3 KB, 37 views)
File Type: jpg 20130204_145605.jpg (144.4 KB, 48 views)
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Old 4th February 2013, 08:19 PM   #278
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Quote:
Originally Posted by bcmbob View Post
Again, some of my confusion comes from my existing board . It is using the "3 point" configuration with dual secondaries. I believe you are saying that will work but is not optimal for this particular application. Is that correct?
It is not optimal for your transformer--Using center tap power board with dual secondaries transformer causes "poorer regulation" and what that does is make the transformer act like it has less VA, so then the bass and dynamics falter due to early onset of transformer throttling. See also post#274
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Here is the latest. Am I getting close?
Oh yes, the latest photos of the handmade stuff looks correct.
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Old 4th February 2013, 08:22 PM   #279
bcmbob is offline bcmbob  United States
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Thanks, what are your recommendations for the main buses? I've seen big wires, plates, strips of copper and of course PCBs (perfboards).
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Old 4th February 2013, 08:59 PM   #280
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Thanks, what are your recommendations for the main buses? I've seen big wires, plates, strips of copper and of course PCBs (perfboards).
Well, what I use is 12ga or 14ga Romex, solid copper. I have to sand the coating off first. And then the wire is so darned thick that it is difficult to solder and takes a rather strong soldering iron.
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