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Old 26th January 2011, 01:37 AM   #1
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Default leach amp power supply

i hope someone can help me with this. im building the leach superamp and cant get correct PS voltages. i have a plitron 117052201 centre tap toroid transformer with give or take 2 60-65 VAC secondary. i have it wired up according to plitrons instruction, aswell as leach super amp instrucions. 130VAC on secondary (65-0-65). once i put the filter caps in the circuit, rectifier "+" to one cap "+", rectifier "-" to the other cap "-" and the centre tap to remaining "+" & "-" i am getting 170 VDC, when it is supposed to anywhere between 85 - 93 VDC, why am i getting more voltage after rectification, as far as i knew you get less once it is DC.......WWWWWHHHHHHHHYYYYYYY, HHHHHEEEEELLLLPPPP!!!!!!

Last edited by rookie amp builder; 26th January 2011 at 01:48 AM.
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Old 26th January 2011, 02:14 AM   #2
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hi rookie amp builder,

Are you talking about 85-0-85 ?

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Last edited by Greg Erskine; 26th January 2011 at 02:20 AM. Reason: Reread original post
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Old 26th January 2011, 02:33 AM   #3
pooge is offline pooge  United States
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How are the primaries connected?
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Old 26th January 2011, 02:37 AM   #4
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read this and if you still have questions ask again

http://www.hammondmfg.com/pdf/5c007.pdf
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Old 26th January 2011, 04:56 AM   #5
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hey, thanx for the responses.

Keeping in mind this is a center tap secondary and i get 130VAC (65+65) which to my knowledge and accodring to leach super amp instructions is the correct voltage

the pimaries are wired brn/blk & wht/org plugged into the wall, according to plitron http://www.plitron.com/standard-toroidal-transformers/power-transformers/international/#SchematicDrawings the schematics for primary and secondary are on that page.

the power supply schematic for the amp is here http://users.ece.gatech.edu/mleach/lowtim/pwrsply.html

This is a quote from super amp site

T1 - The transformer should have either a center tapped secondary or two separate secondary windings which can be wired in series. With 120 V ac rms applied to the primary, the no load secondary voltage should be 120 to 130 V ac rms for a center tapped secondary or 60+60 (60x2) to 65+65 (65x2) V ac rms for two secondary windings. This should give a no load amplifier power supply voltage of plus and minus 85 to 93 V dc. Some transformers are rated at 115 V ac rms on the primary. With 120 V ac rms applied, the secondary voltage will be greater by a factor 120/115. If the transformer is rated at full load, its no load voltage will be 15% to 20% higher. I would recommend a transformer current rating of at least 6 A. The transformer I used in each of my two original Double Barreled Amplifiers was the Signal 230-6. It had two center tapped 115 V 6 A secondaries which I wired in parallel to obtain a secondary rating of 115 V at 12 A. The primary had three voltage taps: 105 V, 115 V, and 125 V. I wired the AC line input to the 115 V tap. With 120 V AC applied to the 115 V tap, I got plus and minus 85 V DC on the power supplies and 270 W into an 8 ohm load. If I had used the 105 V primary taps, the power supply voltage would have increased to about 93 V and the amplifiers would have put out over 300 W. The Signal transformer was definately an overkill. It weighed 38 pounds. But it would really kick you know what. To my knowledge, this transformer now is available only by special order

now with my transformer, rectifier, and filter caps (100V 15000uFD) wired exactly like this, at the point where i connect to the boards i get 170VDC, when im only supposed to get 85 - 93 VDC with or without load (3 incandescent light bulbs in series). when i measure voltage on each cap i get the specified 85VDC, but am only using the potential of one capacitor
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Old 26th January 2011, 05:55 AM   #6
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The super amp site says the DC voltage should be "plus and minus 85 to 93 V dc", or 170 to 186 V between the rails, which is exactly what you get (170 V). You got everything right.
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Old 26th January 2011, 06:13 AM   #7
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Quote:
Originally Posted by alexcp View Post
The super amp site says the DC voltage should be "plus and minus 85 to 93 V dc", or 170 to 186 V between the rails, which is exactly what you get (170 V). You got everything right.

You are a fantastic individual, that is what i was guessing (hoping) but didnt want to fry anything before hand, i never did understand the plus and minus, i was figuring simply as positive and negative. im working up the courage right now to power the unit for the first time (i started this project in 1996) dont ask
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Old 26th January 2011, 09:21 AM   #8
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Good luck You got voltages correct, but there is still a possibility of frying something with this kind of voltages and power. The usual caution is to use a variac when powering it for the first time and increase the mains voltage gradually. Alternatively, you can connect a 100W or so incandescent light bulb in series with the primary, just in case. If it shines bright on power-up, you need to check your power supply for problems...

Last edited by alexcp; 26th January 2011 at 09:24 AM.
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Old 26th January 2011, 12:42 PM   #9
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Are you talking about super amp or low TIM.

Low TIM should use a 40-0-40 AC volts transformer to get plus and minus 56 volts DC
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