Samson Auro D415 powered PA speaker schematic needed

[km6xz]

I have a D415 with DC offset and would love to find a schematic for it. The 15in driver is having a new VC wound for it, but the power amp needs some work. Samson has it on their service web site but I do not have an account any more since I am not an authorized service center now.

[Jazz P Bass]

What an interesting design they used, huh?

I think that Samson is outsourcing there design.

I have never seen such crap.

I had five of these come through in the past month, all had really bad soldering.

[km6xz]

One thing for sure, the power amp can destroy the puny VC in their 15 in diver. I got a pair in, one had open woofer that turned out to be the braided flex wire from the VC to terminal strip had flexed itself to death, easy fix but its horn was smoked. Both amps in that unit were OK. The second has a frozen VC on the woofer and burned open horn diaphragm. The power amp has full DC offset.
I can't get horn VC here, or speaker re-cone kits but found a crusty old submarine officer who as a hobby rebuilds speakers. The guy is a real craftman. Makes his own cast frame, paper cones, winds his own voice coils, magnetizes his own magnets etc.
So far, sending drivers to him for the last year, about 24 of them, none have every failed. He will rewind this VC and make the speaker look like new with new dust cap and surround for 800-900 Rubles, about $25 in 3-4 days.
He rented a little office/shop in an old rubber factory that was a major producer in the 1800s. It has been turned into hundreds of small offices and practice studios, with very little renovation been done. It really looks like an abandoned factory, perfect for the many hard rock and death metal groups who rent all the spaces for private rehearsal rooms. He has a bed there and the messiest tiny shop you could imagine. He goes there every day for several hours just to get away from the wife.


Update: Thanks for the heads up on the bad soldering. I starting inspecting and taking some basic measurements and found a power resistor that was not soldered which fell on the bench when wiggling. Soldered it in and the amp works:>)

[Jazz P Bass]

Schematic is here: http://music-electronics-forum.com/t37702/#post363192

[eaelec]

What an interesting design they used, huh?

I think that Samson is outsourcing there design.

I have never seen such crap.

I had five of these come through in the past month, all had really bad soldering.

I have a Samson D412 in my shop now, the soldering on this one is excellent, maybe they switched to a different contract assembly firm.

The problem was the 12 inch speaker, voice coil shorted out. The electronics survived with just one blown 4 amp fuse on the power amp board.

[J M Fahey]

Yes, +/- 84V rails smash any voice coil.

Brochures boast of "500W / 1000W / 1200W" speakers but truth is anything above Ļ*real* 200/250W continuous is iffy at best.

Speakers are 1% or 2% efficient, and nthat in nthe PA realm, so always >95% of power is turned into plain old heat.

Now try to hold a 100W bulb in your hand .... you canīt.
100W into a speaker VC produces exact same amount of heat.

I mention 200/250W because at that power dissipation you reach, say, 130/150C at the voice coil itself and modern adhesives can *just* stand that.

But at real continuous >500W voice coil "would" need to stand, say, at least 250/300C and that with very clever designs, such as cooling holes and slots, split coils as in JBL EON, etc.
Think again.

So Samson melting voice coils into a copper puddle with such high power amps is not a surprise.

[bsco]

One thing for sure, the power amp can destroy the puny VC in their 15 in diver. I got a pair in, one had open woofer that turned out to be the braided flex wire from the VC to terminal strip had flexed itself to death, easy fix but its horn was smoked. Both amps in that unit were OK. The second has a frozen VC on the woofer and burned open horn diaphragm. The power amp has full DC offset.
I can't get horn VC here, or speaker re-cone kits but found a crusty old submarine officer who as a hobby rebuilds speakers. The guy is a real craftman. Makes his own cast frame, paper cones, winds his own voice coils, magnetizes his own magnets etc.
So far, sending drivers to him for the last year, about 24 of them, none have every failed. He will rewind this VC and make the speaker look like new with new dust cap and surround for 800-900 Rubles, about $25 in 3-4 days.
He rented a little office/shop in an old rubber factory that was a major producer in the 1800s. It has been turned into hundreds of small offices and practice studios, with very little renovation been done. It really looks like an abandoned factory, perfect for the many hard rock and death metal groups who rent all the spaces for private rehearsal rooms. He has a bed there and the messiest tiny shop you could imagine. He goes there every day for several hours just to get away from the wife.


Update: Thanks for the heads up on the bad soldering. I starting inspecting and taking some basic measurements and found a power resistor that was not soldered which fell on the bench when wiggling. Soldered it in and the amp works:>)

I have three of these here now.....was the resistor in question R41 by some chance??? I do realize that this post is older but just thought I would ask to see if you remember.....
Cheers

[bsco]

One thing for sure, the power amp can destroy the puny VC in their 15 in diver. I got a pair in, one had open woofer that turned out to be the braided flex wire from the VC to terminal strip had flexed itself to death, easy fix but its horn was smoked. Both amps in that unit were OK. The second has a frozen VC on the woofer and burned open horn diaphragm. The power amp has full DC offset.
I can't get horn VC here, or speaker re-cone kits but found a crusty old submarine officer who as a hobby rebuilds speakers. The guy is a real craftman. Makes his own cast frame, paper cones, winds his own voice coils, magnetizes his own magnets etc.
So far, sending drivers to him for the last year, about 24 of them, none have every failed. He will rewind this VC and make the speaker look like new with new dust cap and surround for 800-900 Rubles, about $25 in 3-4 days.
He rented a little office/shop in an old rubber factory that was a major producer in the 1800s. It has been turned into hundreds of small offices and practice studios, with very little renovation been done. It really looks like an abandoned factory, perfect for the many hard rock and death metal groups who rent all the spaces for private rehearsal rooms. He has a bed there and the messiest tiny shop you could imagine. He goes there every day for several hours just to get away from the wife.


Update: Thanks for the heads up on the bad soldering. I starting inspecting and taking some basic measurements and found a power resistor that was not soldered which fell on the bench when wiggling. Soldered it in and the amp works:>)

I realize that this is an older post but do you remember what resistor was the issue?? I have one of these here and R41 had a broken lead under the body which was not visable to the eye....it was the cause of 85V dc offset on the speaker connector.....
Cheers