Home Brew Al K Universal crossovers.

[NavLinear]

That should do it..

What about the cap - it didn't fare too well. I should send some of our hardware to you for destructive testing.

 

[laatsch55]

I'm really good at it. I believe the cap was too close to the resistor, but I'm getting some funny numbers off my "Blue ESR " meter. In the mid 24uf paired and paralleled caps, I'm getting 765K on the Fluke in resistance mode and the ESR meter shows .01... Uf on the midcaps show right but why the extreme ohmage?

 

[NavLinear]

I'm really good at it. I believe the cap was too close to the resistor, but I'm getting some funny numbers off my "Blue ESR " meter. In the mid 24uf paired and paralleled caps, I'm getting 765K on the Fluke in resistance mode and the ESR meter shows .01... Uf on the midcaps show right but why the extreme ohmage?

The two meters measure this differently. The ESR meter should provide a pulse that does not charge up the capacitor and a "normal" Fluke multimeter when measuring resistance will provide a constant voltage - hence charging the cap. This may why you're seeing a delta between the two meters.

 

[laatsch55]

Why would a charged cap read more resistance?

 

[laatsch55]

I see the resistance build the longer the Fluke is hooked up, I can infer a few things from that..

 

[laatsch55]

I cut the 4-10 ohm-5watt resistors out of circuit, 1.3megoms, no wonder they sound like shit.....

 

[NavLinear]

Why would a charged cap read more resistance?

You want to measure the equivalent series resistance (ESR) of real capacitors so most ESR meters will apply a voltage pulse to the capacitor with the pulse duration less than what it would take to appreciably charge the cap so the voltage measured across the capacitor is due to the resistance drop - aka ESR. Most ESR meters have a selection range of discrete frequencies to test the capacitor at frequencies where it matters most. When the capacitor if fully charged the characteristics change and an accurate ESR value is not obtainable - as I understand it.

 

[laatsch55]

So short all electros before ESR testing?

 

[NavLinear]

So short all electros before ESR testing?

If you're measuring a big ass cap that was energized prior to making an ESR measurement - I'd say yes. The small ass caps I wouldn't worry about. The big ones take a while to discharge but the tiny ones not so much.

 

[laatsch55]

Shouldn't be any residual in a metalized poly anyway, should there??

 

[laatsch55]

The soldere was gone off the post the autotransfomer was tied to also, so there was quite a few issues here. The wire was loose to the touch on one side..

 

[NavLinear]

Shouldn't be any residual in a metalized poly anyway, should there??

What's the biggest poly you can get now? Something like 10 uF? Those will discharge quickly but all caps store energy - it's the discharge rate that is important when hooking up a meter to them to get a decent ESR reading.

 

[NavLinear]

The soldere was gone off the post the autotransfomer was tied to also, so there was quite a few issues here. The wire was loose to the touch on one side..

Looks like you've got to find out the root cause of the failure.

 

[laatsch55]

The root cause was too much f&^%$#@ power, but what to do about it. If I make this section bullet proof, what goes next. The resistors I'll go with something different but the caps may be my saving grace here....

 

[laatsch55]

Dennis, the big poly's I'm running in these are 24uf, 2 of them in parallel, 200 volters, bypassed by a 200 volt 2.2uf. The tweets are 2- 3.6uf 200 volters bypassed by a 200 volt 2.2 .

 

[NavLinear]

The root cause was too much f&^%$#@ power, but what to do about it. If I make this section bullet proof, what goes next. The resistors I'll go with something different but the caps may be my saving grace here....

Ok - I agree that you don't want the speakers as your weak link. I'm shocked that it was because of too much F$^%#@ power.

 

[laatsch55]

I was vibrating the eyeballs and was going for blurred vision....

 

[NavLinear]

Dennis, the big poly's I'm running in these are 24uf, 2 of them in parallel, 200 volters, bypassed by a 200 volt 2.2uf. The tweets are 2- 3.6uf 200 volters bypassed by a 200 volt 2.2 .

Damn - the current and resulting heat is taking these guys out. Which one(s) are getting cooked? You could go with higher voltage rated caps but can the speakers take it?

 

[laatsch55]

I'm not sure the caps are bad, they test good on the ESR meter, .01 or less and are spot on with the uf check section of the Fluke. The burnt one was too close to the resistor....

 

[NavLinear]

I'm not sure the caps are bad, they test good on the ESR meter, .01 or less and are spot on with the uf check section of the Fluke. The burnt one was too close to the resistor....

Will you use a heat sink for the thick film resistor? Maybe a bit more separation between the power resistor and cap will help. I wonder what temp those guys were subjected to? Had to be pretty hot to melt the solder and destroy the resistors and cap.