Behringer ACX1000, IC3 pinout

[ChancesR]

The board in question is PCB408060REVH/03. IC3, LM3886T - pin 11. (Counting from pin 1 there are 6 pins in front, then beginning right behind pin 6 with pin 7 again.) The last pin (pin 11) I noted does not have the pad on the board. I have tried using a lightbox - and still cannot figure out where this pin should go -if anywhere. I know Behringer schematics are a no-no (shame on them!) - but if someone could please let me know the proper location for this I would be happy it's a Monday.

Regards,
C

[Enzo]

Just look at the data sheet for the LM3886. Either just google LM3886 or go to NAtional Semiconductor site and look it up there. Nothing special about it, it is the same LM3886 used by many manufacturers.

Pin 11 is not connected in the chip. Neither are pins 2 and 6.

It is a standard 11 pin TO220, it just doesn't use all the pins. Behringer doesn't run a trace to it for that reason.

Behr is a funny company, but they are still tender about the major loss of a lawsuit brought by Mackie some years back over copyright or patent infringement. Part of defending claims of infringement is how much access to your designs people outside your company have. They keep close watch as possible over their data.

[ChancesR]

Thank you again Enzo. About the Behr issues.....I totally understand that. Weren't there some issues with QSC also? I remember working on a Behringer amp a few years back that I used a QSC schematic for - perfect match. Don't remember the model now - but someone posted that it was a little 'peculiar'.

I had pulled the spec sheet for the LM3886 - but this project has been such a dog, I'm doubting myself a bit too much. Hate it when that happens.

Good fixin's to all -
C

[raytclark]

ACX1000 effects issues

ChancesR, just wondering if you got anywhere with your diagnostics. I'm guessing this is the Model DPM4 board. Mine is PCB307070revG so you have the more recent design but apparently they still have an issue? I've checked to find the boards are backordered from Behr and so I was hoping you figured out the repair? I would love to get this board working instead of waiting indefinitely for a replacement. Thanks in advance for your time. -Ray

btw. mine makes about a 4 second cycle of pshhhh...getting slightly louder... then pops and starts all over.

[ChancesR]

I wish I had better news for you on this. Although I truly hate letting something get the best of me, I practically rebuilt the whole board - and still had the problems. Since Enzo explained the legalities of obtaining any info from Behr, I suggested to the customer to send it to an authorized service center. So on my end...case closed. I'm sorry I couldn't have posted a "fix" here.

Regards,
ChancesR

[Enzo]

And i am sorry I could be no more help than that.

[mikeboone]

What a blast from the past... I built a few amps with these, a mono block with an LM3876 and a stereo amp with a pair of 3886's

Have you replaced it? I think I may have a few laying around my shop somewhere.

[ChancesR]

Lm3886

Yes, replaced both of them. I had one of those moments when I just *knew* this would take care of the problem. But no. ha

Enzo - You are tremendous help! I would love to follow you through a work-week (or year!). I would learn SO much. I totally understand the situation, and even just knowing that's "how it is" was greatly appreciated. Saved me hours and hours of skull cramps. Thanks so much.....

[Enzo]

You'd discover all the myriad ways I find to waste time each day, and of course where I get pictures of naked cheerleaders.