lm3886 - dc on output

Wizardmaxx · 20th October 2009, 04:38 PM

Hi

Bought one of them cheapy's off fleabay.

Problem is that one channel works....and very well at that, other channel has 35v dc on the output. Should have checked before I connected speaker.

Any ideas or is it as simple as chip doa.

Wizard

Minion · 20th October 2009, 11:41 PM

Check that you have connected the PSU to the Chip amp correctly and that you are getting the correct voltages at the Power pins of the LM3886 , usually if there is that much DC at the output it is because the chip isn"t getting power on one of the Rails ....

Good luck

Wizardmaxx · 21st October 2009, 06:52 AM

Thanks Minion

Checked the voltages and strangely got 35V between pins 9 and 10. Should this not be 70V. Other than that all seems to measure out ok.

The beast in question is the following.

rem280 · 21st October 2009, 09:50 AM

Pins 9 and 10 are Vin+ and Vin- not V+ and V- you should mesure no voltage between the two. The difference between these pins will be amplified by how ever much gain the amplifier has and move the output to just the positive or negative rail. You need to figure out what the cause of this voltage is I don't have a schematic for your amp and your picture isn't working so Im not sure what to check first but it sounds like there is a short to power somewhere or something hooked up wrong.

Wizardmaxx · 24th October 2009, 07:54 AM

Just a quick update on voltages.

Pin1 to ground +36.2
Pin4 to ground -36.1
Pin3 to ground +34.6
Pin9 to ground +34.1
Pin3 to Pin5 +1.4v

Any ideas. I am assuming the chip is fried as there is virtually full +ve supply on the input pin with the exception of the 1.4v between pin3 and +ve rail

20th October 2009, 04:38 PM	#1
Wizardmaxx diyAudio Member Join Date: Oct 2009	lm3886 - dc on output Hi Bought one of them cheapy's off fleabay. Problem is that one channel works....and very well at that, other channel has 35v dc on the output. Should have checked before I connected speaker. Any ideas or is it as simple as chip doa. Wizard

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
LM3886 + output transistor	luixssj3	Chip Amps	5	16th March 2009 04:24 AM
LM3886, 20v at output	ryan750	Chip Amps	18	17th November 2008 02:05 PM
Low output power with LM3886??	Minion	Chip Amps	13	8th November 2006 06:29 PM
LM3886 output impedance	alexw88	Chip Amps	2	11th June 2005 03:58 AM
lm3886-dc on the output	xplod1236	Chip Amps	70	29th January 2004 09:48 AM

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read


	Please consider donating to help us continue to serve you. Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving

20th October 2009, 11:41 PM	#2
Minion diyAudio Member Join Date: May 2006	Check that you have connected the PSU to the Chip amp correctly and that you are getting the correct voltages at the Power pins of the LM3886 , usually if there is that much DC at the output it is because the chip isn"t getting power on one of the Rails .... Good luck

21st October 2009, 06:52 AM	#3
Wizardmaxx diyAudio Member Join Date: Oct 2009	Thanks Minion Checked the voltages and strangely got 35V between pins 9 and 10. Should this not be 70V. Other than that all seems to measure out ok. The beast in question is the following.

21st October 2009, 09:50 AM	#4
rem280 diyAudio Member Join Date: May 2009	Pins 9 and 10 are Vin+ and Vin- not V+ and V- you should mesure no voltage between the two. The difference between these pins will be amplified by how ever much gain the amplifier has and move the output to just the positive or negative rail. You need to figure out what the cause of this voltage is I don't have a schematic for your amp and your picture isn't working so Im not sure what to check first but it sounds like there is a short to power somewhere or something hooked up wrong.

24th October 2009, 07:54 AM	#5
Wizardmaxx diyAudio Member Join Date: Oct 2009	Just a quick update on voltages. Pin1 to ground +36.2 Pin4 to ground -36.1 Pin3 to ground +34.6 Pin9 to ground +34.1 Pin3 to Pin5 +1.4v Any ideas. I am assuming the chip is fried as there is virtually full +ve supply on the input pin with the exception of the 1.4v between pin3 and +ve rail

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)