Soft start headache

Buzzy · 26th December 2009, 11:06 AM

I built rod elliot project 39 the soft start circuit. Right now the circuit is working. However the transformer i use for the soft start is driving me nuts. The transformer is center tapped 6VA 9-0-9V. I measured the transformer without anything connected and it gives me 9V ac. But when i connect the soft start circuit to it, one side gives me 9.3V ac and the other side gives me 18V ac. How could this be possible ? I tried checking the connections again and again but can't point out what is wrong. Can anyone tell me what i should check ?

Mooly · 26th December 2009, 11:50 AM

Has the transformer ONLY 3 pins. 9-0-9 or is it two separate windings of 0-9 and 0-9 and has four pins

jaycee · 26th December 2009, 01:25 PM

For a 6VA transformer, a softstart isn't neccesary anyway... you will be fine with an appropriately rated "T" type (slow blow/time delay/anti surge) fuse.

Buzzy · 26th December 2009, 02:21 PM

The transformer has 3 pins 9-0-9.

Jaycee the 6VA transformer i am talking about is to power the soft start circuit. The soft start circuit is made to power a 500VA transformer.

Mooly · 26th December 2009, 04:41 PM

Hmmm... as ever wihout actually seeing something...

OK... meter on AC, transformer not conected to anything, and putting one meter lead on the center 0v ? (it usually is the center but not always) pin and reading with the other lead to either of the other pins should give 9 vac.
Connecting to the circuit, and repeat exactly and it has to be the same

perhaps slighly lower as now under load.
Your not measuring the rectified AC or anything ?

boraomega · 26th December 2009, 05:03 PM

Maybe this might be helpfull...

Buzzy · 26th December 2009, 05:05 PM

Quote:

Originally Posted by Mooly

Hmmm... as ever wihout actually seeing something...

OK... meter on AC, transformer not conected to anything, and putting one meter lead on the center 0v ? (it usually is the center but not always) pin and reading with the other lead to either of the other pins should give 9 vac.
Connecting to the circuit, and repeat exactly and it has to be the same

perhaps slighly lower as now under load.
Your not measuring the rectified AC or anything ?

I did exactly as u said. 9V ac with nothing connected. But when i connect to the soft start circuit the meter gives me 9V ac on one side and the other side (the other pin) is 18V ac. The 0V pin is at the center. I put one end of the meter lead at the center, kept it fixed. The other lead to measure the 9V pins . I am very sure i did not put the meter leads across the 9V pins. This is so crazy..........ARGHHHHH. I don't understand why.

Buzzy · 26th December 2009, 05:09 PM

Quote:

Originally Posted by boraomega

Maybe this might be helpfull...

Sry but what is that circuit for ? Is that another soft start ?

boraomega · 26th December 2009, 05:17 PM

Left circuit is a soft-start and right one is remote ON/OFF power switch.

Buzzy · 26th December 2009, 05:22 PM

Quote:

Originally Posted by boraomega

Left circuit is a soft-start and right one is remote ON/OFF power switch.

The soft start you gave seems like it is powered by the main transformer of the amp itself. Forgive me if i am wrong.

26th December 2009, 11:06 AM	#1
Buzzy diyAudio Member Join Date: Apr 2007	Soft start headache I built rod elliot project 39 the soft start circuit. Right now the circuit is working. However the transformer i use for the soft start is driving me nuts. The transformer is center tapped 6VA 9-0-9V. I measured the transformer without anything connected and it gives me 9V ac. But when i connect the soft start circuit to it, one side gives me 9.3V ac and the other side gives me 18V ac. How could this be possible ? I tried checking the connections again and again but can't point out what is wrong. Can anyone tell me what i should check ?

26th December 2009, 05:17 PM	#9
boraomega diyAudio Member Join Date: May 2005 Location: Cacak, Serbia	Left circuit is a soft-start and right one is remote ON/OFF power switch. __________________ If you are arguing with an idiot, first make sure that he is not doing the same thing.

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26th December 2009, 11:50 AM	#2
Mooly diyAudio Member Join Date: Sep 2007	Has the transformer ONLY 3 pins. 9-0-9 or is it two separate windings of 0-9 and 0-9 and has four pins

26th December 2009, 01:25 PM	#3
jaycee diyAudio Member Join Date: Apr 2004 Location: Norwich, UK	For a 6VA transformer, a softstart isn't neccesary anyway... you will be fine with an appropriately rated "T" type (slow blow/time delay/anti surge) fuse.

26th December 2009, 02:21 PM	#4
Buzzy diyAudio Member Join Date: Apr 2007	The transformer has 3 pins 9-0-9. Jaycee the 6VA transformer i am talking about is to power the soft start circuit. The soft start circuit is made to power a 500VA transformer.

26th December 2009, 04:41 PM	#5
Mooly diyAudio Member Join Date: Sep 2007	Hmmm... as ever wihout actually seeing something... OK... meter on AC, transformer not conected to anything, and putting one meter lead on the center 0v ? (it usually is the center but not always) pin and reading with the other lead to either of the other pins should give 9 vac. Connecting to the circuit, and repeat exactly and it has to be the same perhaps slighly lower as now under load. Your not measuring the rectified AC or anything ?

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