leach amp output problem

squarehdca · 7th February 2005, 07:58 PM

I have just finished building a v4.5 leach amp . All the parts are recommended , ther is +/- 57v idle and 54 v loaded at the rails. When fed a 1 v 1khz signal the output wave is perfect and there is approx 37 v at he output terminals. However when I hook up an 8 ohm 100 watt resistor the output siganl drops right off in about 10 seconds and stays there. I suspect a problem in the protection circuit however both channels react the same . Any ideas?
Thanks
Ed Q.

JensRasmussen · 7th February 2005, 08:50 PM

Sound like power supply trouble to me - not sure though.....
What is you railvoltage when you apply the 8 ohm load?
What is your transformer VA rating if you know?
If you are unsure, how much does it weigh?
\Jens

squarehdca · 7th February 2005, 09:17 PM

Under load there is +/- 54 v , adequate according to specs ,it is an 800 va toriodal transformer. I have another one available to test.

squarehdca · 7th February 2005, 10:34 PM

Swapped in a 700 va 80 vct transformer and now all is well .
Thanks for the input , it got me looking in the right place.

AndrewT · 8th February 2005, 07:24 AM

Hi, glad to hear the problem went on holiday with the transformer swap.
But what was the problem?
regards Andrew T.

Upupa Epops · 8th February 2005, 08:51 AM

Control again values of all devices - if makes both channels the same, problem will be there.

squarehdca · 8th February 2005, 09:28 PM

Problem was found in a small fault in windings of transformer, center tap was not going to ground properly , loss of voltage under load.

7th February 2005, 07:58 PM	#1
squarehdca diyAudio Member Join Date: Mar 2004 Location: southern ont	leach amp output problem I have just finished building a v4.5 leach amp . All the parts are recommended , ther is +/- 57v idle and 54 v loaded at the rails. When fed a 1 v 1khz signal the output wave is perfect and there is approx 37 v at he output terminals. However when I hook up an 8 ohm 100 watt resistor the output siganl drops right off in about 10 seconds and stays there. I suspect a problem in the protection circuit however both channels react the same . Any ideas? Thanks Ed Q.

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7th February 2005, 08:50 PM	#2
JensRasmussen diyAudio Member Join Date: Jul 2002 Location: Denmark - Jutland	Sound like power supply trouble to me - not sure though..... What is you railvoltage when you apply the 8 ohm load? What is your transformer VA rating if you know? If you are unsure, how much does it weigh? \Jens

7th February 2005, 09:17 PM	#3
squarehdca diyAudio Member Join Date: Mar 2004 Location: southern ont	Under load there is +/- 54 v , adequate according to specs ,it is an 800 va toriodal transformer. I have another one available to test.

7th February 2005, 10:34 PM	#4
squarehdca diyAudio Member Join Date: Mar 2004 Location: southern ont	Swapped in a 700 va 80 vct transformer and now all is well . Thanks for the input , it got me looking in the right place.

8th February 2005, 07:24 AM	#5
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	Hi, glad to hear the problem went on holiday with the transformer swap. But what was the problem? regards Andrew T.

8th February 2005, 08:51 AM	#6
Upupa Epops diyAudio Member Join Date: Aug 2003 Location: Prague,Czech Republic	Control again values of all devices - if makes both channels the same, problem will be there.

8th February 2005, 09:28 PM	#7
squarehdca diyAudio Member Join Date: Mar 2004 Location: southern ont	Problem was found in a small fault in windings of transformer, center tap was not going to ground properly , loss of voltage under load.

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