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Old 14th March 2008, 09:18 AM   #1
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Default Summing 2 GFA-555 toroidals

I have two toroidals from GFA-555's. I want to sum them to 2 large caps. I want one 80vdc-, and one 80vdc+. I think the best way to do this would be to rectify all the secondaries separately, and combine all the DC voltages. I am building a very powerful 2ohm amp for subs, and need lots of currant. I hear you can parallel secondaries, but I feel separate rectifiers would be better. What do you guys think?
Thanks much
Ben
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Old 15th March 2008, 12:17 AM   #2
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Seperate recifiers are safer and dependable, no voltage mismatch current flowing in transformer.............

Also, if you have TWO transformers, you could run the secondaries in series, you could use each transformer for a rail, one for positive, and one for negative rail. It would use less rectifiers too.

If you can't do that, then just parallel the outputs from each transformer after the rectifier diodes,
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Old 15th March 2008, 03:41 AM   #3
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Thanks EW. That confirms my original plan. Where in Fla are you? I am in FT Lauderdale.
Ben
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Old 15th March 2008, 05:21 AM   #4
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I'm in Lakeland.

I just wish there was some people around here that shared common interests or hobbies! Most people I know can barely twist wires, so talking amps and electronics to them is like speaking greek.

Also, it's hard to find a good electronics store. I have to get everything online or drive really far to Skycraft Surplus in Winter Park (past Orlando on I-4) RadioShack has only a FEW things, which has declined over the years.

Glad to see another fellow Floridian enjoying the DIY hobby lifestyle!
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Old 15th March 2008, 07:34 AM   #5
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I hear ya. Too bad you are so close yet so far. The reason I fixed my GFA-585 was I don't trust the repair shops down here. I am moving to Conyers GA. I hope things are better there. Rat Shacks don't have anything anymore, or I am just too demanding?

Ben
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Old 17th March 2008, 12:03 AM   #6
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I used to work at Radio Shack. They started cuttinf back the parts because they dibn't sell as fast as they wanted. Sucks, now they hardly have any good IC's, or transistors, few power resistors and prices went up on most of that kind of stuff.
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Old 17th March 2008, 03:26 PM   #7
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When Radio Shack stopped printing the annual catalog, it was the beginning of the end. In the old days I could have my wife run by the RS store and get a #15-123. Now almost all the parts are in one big cabinet.
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Old 17th March 2008, 11:25 PM   #8
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Quote:
Originally posted by Speedskater
When Radio Shack stopped printing the annual catalog, it was the beginning of the end. In the old days I could have my wife run by the RS store and get a #15-123. Now almost all the parts are in one big cabinet.
Your wife must be pretty cool to do that for you. DIY friendly wife!

I worked at RS during that last year of the catalog with the ugly chick on the front. What a crazy year!

RS doesn't carry regular 14pin IC sockets in most of their stores!!!! WTF! Sockets are so important for DIY with IC's, in case there's a failure, who wants to desolder an IC on something you made yourself? I'd rather swap IC's like you swap CPU's in a computer.

Back to the thread topic........Yea, just parallel after rectifiers and you are fine. There CAN be exceptions, but better safe than sorry.

Speaking of....
I did make an unregulated 6V/12V 3/12 amps power supply, when I was a teenager. It has four identical 12V, 3A transformers from RadioShack, and I paralleled 3 out of the 4 transformers directly in phase. I never had problems. The primary power was a single 12V 3A transformer with bridge and caps, and when I flipped a switch, It added 9A more through another bridge, and more filter caps. The 3 transformers on the 9A side connected as one. This power supply lasted over 12 years and counting.
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