LM 3886 18v at output

[nickalpha]

i am having a serious problem my gainclone amp is outputting 18 volts measured from pin 3 and pin 7 (ground) what is it i am doing wrong

 

[6L6]

Post some well-lit, in-focus photos of your build and the exact schematic you are using.

 

[adason]

3886 is robust chip amp, it has all sorts of protection.
But no protection from wrong wiring.
Post schematics you are following. Post pictures, lots of it, high quality. We may be able to spot something. I have seen people use single supply with no cap on the output...then they wonder why it does not work.

 

[edbarx]

I will soon build two amplifier channels using this chip when my order arrives home. The PCBs have been made quite neatly using the acetone toner transfer method and a solution of hydrogen peroxide plus muriatic acid as etchant. The remaining step is to carefully inspect all the tracks for minute shorts with a magnefying glass. After that, I will check that the PCBs comform with the chip's pinouts. Misplaced schematics in the internet are not an impossibility.

 

[nickalpha]

I am using the data sheet schematics on perfboard

 

[Mark Tillotson]

Have you measured the voltage rails? Voltage on the feedback resistor?

 

[nickalpha]

no i did not measure the voltage there i am suing a 20k feedback resistor

 

[nickalpha]

i measure the voltage across the feedback resistor i got -2.5 mV

 

[Mark Whitney]

Without photos it is going to be very difficult to workout what you have done wrong.

 

[nickalpha]

Hey Guys thanks very much for your replies. i finally figure it was my PSU the bridge was wrong give 33 and -8 so i replace the bridge and it work!!!!!
i fried one of my chips though lol

 

[adason]

That's pretty much what i described as powering it with single supply. You are supposed to check the power supply independently before plugging it into an amp.
Glad you sorted it out. Enjoy.