Mains Relay blowing Fuse on GC

k3ys3r_soz3 · 6th March 2007, 02:49 PM

I had built myself a gainclone a couple of years ago with briangt's 3785 kit - this has been working flawlessly up until this week.

I recently got a new pre-amp with a 12v trigger.

I though - oh goodie I can use that to trigger a relay to turn my GC on automatically - the missus will like that

Well I purchased a 12v 10amp 250v relay - wired it all up - tested it - switches on and off as expected.

Indeed it seemed to work fine for a couple of days.

Yesterday I switch on my PRe - nothing - open the GC and notice the fuse (2amp slo blo) on my primary of the TX has blown.

Swap it out - retry - I turn the pre on and it works - turn it off - fine - turn it back on again and it blows the fuse again - very frustrating.

Doubled checked all wiring - all fine.

Removed the relay - can switch the gainclone on with my rocker switch on the back fine - on/off/on/off ad nausem and the fuse is fine.

Any ideas?

peranders · 6th March 2007, 05:09 PM

If you have a toroid transformer, the relay is too weak. You must either have a softstart or a bigger switch.

If you put 50-100 A (inrush currents) through the poor relay contacts they will pretty soon die.

k3ys3r_soz3 · 6th March 2007, 05:25 PM

thanks

it is a toroid but only 230va - guess I will have to look at soft start

6th March 2007, 02:49 PM	#1
k3ys3r_soz3 diyAudio Member Join Date: Jun 2004 Location: bristol	Mains Relay blowing Fuse on GC I had built myself a gainclone a couple of years ago with briangt's 3785 kit - this has been working flawlessly up until this week. I recently got a new pre-amp with a 12v trigger. I though - oh goodie I can use that to trigger a relay to turn my GC on automatically - the missus will like that Well I purchased a 12v 10amp 250v relay - wired it all up - tested it - switches on and off as expected. Indeed it seemed to work fine for a couple of days. Yesterday I switch on my PRe - nothing - open the GC and notice the fuse (2amp slo blo) on my primary of the TX has blown. Swap it out - retry - I turn the pre on and it works - turn it off - fine - turn it back on again and it blows the fuse again - very frustrating. Doubled checked all wiring - all fine. Removed the relay - can switch the gainclone on with my rocker switch on the back fine - on/off/on/off ad nausem and the fuse is fine. Any ideas?

6th March 2007, 05:09 PM	#2
peranders Electrons are yellow and more is better! diyAudio Member Join Date: Apr 2002 Location: Göteborg, Sweden Blog Entries: 4	If you have a toroid transformer, the relay is too weak. You must either have a softstart or a bigger switch. If you put 50-100 A (inrush currents) through the poor relay contacts they will pretty soon die. __________________ /Per-Anders (my first name) or P-A as my friends call me

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6th March 2007, 05:25 PM	#3
k3ys3r_soz3 diyAudio Member Join Date: Jun 2004 Location: bristol	thanks it is a toroid but only 230va - guess I will have to look at soft start

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