Need to connect mute pin on 3886?

[Hybrid fourdoor]

Just wondering if you need to connect the mute pin on the lm3886 in order for the amp to work. Its the only thing I can think of, mine is unconnected right now. The amp doesn't have any output.

Also, when I turn my amp on and measure the V+ and V-, I get +40V and -14V. Is this normal at idle? I also accidently hooked the transformer up backwards and got +1.4V and -54V the first time, which may have fried my amp, but i heard these things are pretty resiliant to overloads and stuff.

Heres the schematic from national.

 

[ddog]

Yes, you have to connect it with resistor between Mute pin and -V, value calculated so 0,5mA or greater can be drawn from Mute pin.

+V = 40V and -V= -14V doesn't seem normal to me. Are supply electrolyts connected correctly?

 

[seangoesbonk]

Didn't search, did you?

http://www.diyaudio.com/forums/showthread.php?threadid=14497&highlight=

 

[soundNERD]

How did you make your power supply? Did you just use 2 caps, a transformer, and a rectifier? Do you have the schematic you used? Remove the power supply leads from the amp and test them with a multimedia. See what you get.

I think that the low - voltage is because you skipped connecting the mute pin and it is shorting the amp, though. did you skip any resistors/caps either? If so, which ones?

 

[Pan]

Reversing the V+/- has probably fried your chip, happened to my friend when he mixed up the lines.

/Peter

 

[macboy]

Reversing the V+/- has probably fried your chip, happened to my friend when he mixed up the lines.

I agree. These things are pretty resilient when it comes to overheating, difficult loads, etc., but like virtually any semiconductor, reversing the voltage is a very bad thing.