AlephX PSU- need help

bach2800 · 6th July 2006, 02:24 AM

Hi,
I'm building an alexh-x but a problem appear when at the initial testing of the PSU with no load on it. It keep blowing fuse.

I'm using a crc filter with 2 bridge, 56000uF - .25R - 56000uF. The fuse I'm using is 8A slow blow. something like this: http://s37.photobucket.com/albums/e9...nt=LOIC_PS.jpg
The transfo is from ebay, initially 240V input, 4x 38V output rated at 3700VA. I'm running it at 120V and get about 19V per secondary.Let me know if you think you need some more info.

Thanks for your help
Thierry

metalman · 6th July 2006, 03:52 AM

Are you using the NTC shown in the figure you referenced? If not, the initial current draw to charge the capacitors will easily blow the fuse.

Second, have you tried starting the power supply up slowly using a variac? That will give you some clues as to where the mistake might be.

Lastly, a good high wattage power resistor doesn't cost much and will provide a decent load to the power supply for testing purposes.

A few points to try and if they don't work out, we'll try some others.

Cheers, Terry

bach2800 · 6th July 2006, 04:16 AM

I'm using 2 cl-60 one on the hot and one on the neutral
Could it be possible that 8amp fuse is not enough?

I didn't try with a variac but I'll get one tomorrow.

As for the load I have a 33R around 50-100W, would it be good for that purpose? I was not using one so far because I don't want to add more inrush til it work.

Thierry

jh6you · 6th July 2006, 08:05 AM

If it is 3700VA at 120V main, the current handling is about 30A on the main side. In addition, there will be very high inrush current. Probably, there should be fuses on the secondary side too. Ayo . . . have no idea how to estimate the fuse size in this case . . . Nevertheless, the 8A slow blow is considered too small.

TS Lo · 6th July 2006, 01:21 PM

Quote:

Originally posted by jh6you
If it is 3700VA at 120V main, the current handling is about 30A on the main side. In addition, there will be very high inrush current. Probably, there should be fuses on the secondary side too. Ayo . . . have no idea how to estimate the fuse size in this case . . . Nevertheless, the 8A slow blow is considered too small.

In this case - the transformer can only handle about 1800VA since the
copper wire used in the primary winding is only enough for (3700/240)
15 amp.

TS

kropf · 6th July 2006, 03:26 PM

In the absence of a variac, try a light bulb in series with the transformer primaries. This will keep the fuse from blowing and let you look around to see if everything else is working fine.

Jeremy

bach2800 · 6th July 2006, 09:53 PM

Problem solve, I happen to had a short capacitor who was pulling the juice. The variac was very handy in troubleshooting it.

Thank you all for your reply

Thierry

6th July 2006, 02:24 AM	#1
bach2800 diyAudio Member Join Date: Jun 2004 Location: montreal	AlephX PSU- need help Hi, I'm building an alexh-x but a problem appear when at the initial testing of the PSU with no load on it. It keep blowing fuse. I'm using a crc filter with 2 bridge, 56000uF - .25R - 56000uF. The fuse I'm using is 8A slow blow. something like this: http://s37.photobucket.com/albums/e9...nt=LOIC_PS.jpg The transfo is from ebay, initially 240V input, 4x 38V output rated at 3700VA. I'm running it at 120V and get about 19V per secondary.Let me know if you think you need some more info. Thanks for your help Thierry

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
AlephX with 610?	ijomojo	Pass Labs	3	1st September 2005 04:45 PM
Best 1st amp:AlephX, 5 or a Zen?	rif	Pass Labs	7	15th April 2004 04:56 PM
ApexJr AlephX?	tiroth	Pass Labs	5	8th February 2004 12:58 AM
alephx dc offset	lumanauw	Pass Labs	10	24th December 2003 09:15 AM
IRF 230 or IRFP 140, what's better for AlephX ?	Peter Daniel	Pass Labs	29	26th September 2002 03:05 AM

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read


	Please consider donating to help us continue to serve you. Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving

6th July 2006, 03:52 AM	#2
metalman diyAudio Member Join Date: Jun 2003 Location: Calgary, Alberta	Are you using the NTC shown in the figure you referenced? If not, the initial current draw to charge the capacitors will easily blow the fuse. Second, have you tried starting the power supply up slowly using a variac? That will give you some clues as to where the mistake might be. Lastly, a good high wattage power resistor doesn't cost much and will provide a decent load to the power supply for testing purposes. A few points to try and if they don't work out, we'll try some others. Cheers, Terry

6th July 2006, 04:16 AM	#3
bach2800 diyAudio Member Join Date: Jun 2004 Location: montreal	I'm using 2 cl-60 one on the hot and one on the neutral Could it be possible that 8amp fuse is not enough? I didn't try with a variac but I'll get one tomorrow. As for the load I have a 33R around 50-100W, would it be good for that purpose? I was not using one so far because I don't want to add more inrush til it work. Thierry

6th July 2006, 08:05 AM	#4
jh6you Account Disabled Join Date: Aug 2002 Location: Near to the Pacific Ocean	If it is 3700VA at 120V main, the current handling is about 30A on the main side. In addition, there will be very high inrush current. Probably, there should be fuses on the secondary side too. Ayo . . . have no idea how to estimate the fuse size in this case . . . Nevertheless, the 8A slow blow is considered too small.

6th July 2006, 03:26 PM	#6
kropf diyAudio Member Join Date: Dec 2002 Location: Illinois, USA	In the absence of a variac, try a light bulb in series with the transformer primaries. This will keep the fuse from blowing and let you look around to see if everything else is working fine. Jeremy

6th July 2006, 09:53 PM	#7
bach2800 diyAudio Member Join Date: Jun 2004 Location: montreal	Problem solve, I happen to had a short capacitor who was pulling the juice. The variac was very handy in troubleshooting it. Thank you all for your reply Thierry

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)