Fried rectifier bridge in channel relay in d'lite..

[daz]

Hi all,
I was installing 5v relays in my d'lite build based on this circuit running from the heater wires:
http://www.el34world.com/projects/relay_switch3.htm

Switching it on I fried my rectifier bridge (it's smoked then split in two). The one I used was db-155. See spec attached. I'm assuming the current rating for this was not high enough plus the 600v rating was for dc not ac?

Would any of these be below be more appropriate?
http://dseau.resultspage.com/search.php ... &submit=Go

What rectifier bridge should I use?

Cheers
daz

[Bob-I]

What relays are you using? Many of the popular relays can draw u pto an amp. Latch 2 of these and your 1.5A bridge smokes. Personally I usually build a bridge from 4 1N4007's but I've also used a Fairchild 2KBP06M which handles 2A.

[UR12]

Before replaceing the bridge make sure your diode accross the relay coil isn't installed backwards.

[daz]

I'm using 5v Omron G6A-234P-St-US dpdt non latching relays.
So the current draw using two relays won't work on the heater supply?
http://www.omron.com.cn/cma/uploadpic/g6a0984.pdf


Maybe I need a rectifier like this:
http://www.jaycar.com.au/productView.as ... &SUBCATID=

Sorry this is my first attempt at doing something with relays.

[Bob-I]

Your relays are rated a 40ma each, so your rectifier should've been fine.

That said you'll also need to check your heater supply for enough current to handle these relays. Add 80ma to the current draw you already have on the tubes and check against the PT specs.

Overall I'd say you have another problem like a diode backwards or a short.

[jelle]

What is the value of he fitercap right after the diodes? I use a 4700uf here and they ask a lot of current from a diode recifier....the 1 amp IN4007 that I use aross the coil won't keep up with this current demand.

I use 25amp bridge rectifiers for this because of this big cap.

I hope this helps,

Jelle

[daz]

thanks everyone for your help. Hmm maybe I'm confused by the diagram on the link.
I installed the -ve side of the diode across the +ve side of the relay coil.
Wrong? That's what appears in the diagram??

Yep used 2 4700uf filter caps.

[drz400]

Before replaceing the bridge make sure your diode accross the relay coil isn't installed backwards.

Agreed, something is backwards or you are ref to ground somewhere you shouldnt be

[Bob-I]

Yep used 2 4700uf filter caps.

That's way overkill on the filtering. I usually use a single 1000uF.

[daz]

Dang still frying the rectfier bridge.
Did a new power supply, realised I installed the diode across relays wrong and wired wrong (the diagram on the relay was for bottom of the relay, not top! ) however recitifer still smoked.
Yep changed filter caps to 1000uf.

Hmm somethings not right, I'll take some pics.
CHeers
daz

[Bob-I]

Disconnect everything except the input voltage. Once you power up the rectifier and voltage alone successfully, connect up the filters, then the relay.

[lastwinj]

is there a center tap on the 5v winding? if so, and you grounded it, that will cause what you are experiencing. i just did the same thing myself, buring a bridge rectifier. puff of smoke and cracked it.

germ

[daz]

I'm running 6.3v heaters to the ~ bridge, - of bridge to ground, +ve side of bridge to +ve side of the filter caps. I also create a artificial center tap of the heaters with 100ohm resistors to ground.
So I shouldn't have a center tap?
Using this diagram as reference:
[img:339:228]http://www.el34world.com/projects/image ... eeburg.gif[/img]

If I'm adding a footswitch jack does it need to be grounded?

[paulster]

You need to lose the centre-tap on the heaters or the DC connection to ground to get this to work without shorting out the transformer through the bridge.

In this instance I'd lose the DC connection to ground, whereas if I were using DC heaters for the preamp I'd lose the centre-tap connection to ground and use the DC ground as the reference.

You can't have both at the same time unless you create a virtual ground for the DC (the 100R resistors trick) but it shouldn't be necessary for a control circuit such as this.

Your heaters (6.3V AC) should go to the AC terminals on the rectifier. The DC terminals will go to the relay board only. Don't get them anywhere near ground. It'll also require using an insulated (e.g. Cliff) jack for the footswitch.

[Bob-I]

You might try a different ckt. Use a full wave instead of a bridge. I used this successfully in one amp.