lm4780 problem

Jim Karr · 3rd June 2007, 02:29 AM

I've assembled one of BrianGT's LM4780 boards. Turned on the power, no smoke (praise the Lord). No signal from the speakers, just a very infinitesimally small hum. Apparently it's in protection of some sort.

I don't know what voltages and other measurements I should be getting on each pin out. Anyone have any ideas?

No solder bridges, and I've checked my connections several times. It all looks correct. Help?

YFW · 3rd June 2007, 06:32 AM

Please check the output DC voltage which should be very low if everything is in normal condition.

jackinnj · 3rd June 2007, 01:22 PM

Quote:

Originally posted by Jim Karr
I've assembled one of BrianGT's LM4780 boards. Turned on the power, no smoke (praise the Lord). No signal from the speakers, just a very infinitesimally small hum. Apparently it's in protection of some sort.

I don't know what voltages and other measurements I should be getting on each pin out. Anyone have any ideas?

No solder bridges, and I've checked my connections several times. It all looks correct. Help?

How have you connected the MUTE pin?

Jim Karr · 8th June 2007, 10:18 PM

DC voltage is almost nonexistent. It's been so long since I worked on this amp I don't remember the exact value, but I do remember that it was miniscule.

I believe the mute pin is just fed through the board into a plain unclad hole, so it is not connected at all.

Thanks for your responses!

jackinnj · 9th June 2007, 12:38 AM

Quote:

Originally posted by Jim Karr
DC voltage is almost nonexistent. It's been so long since I worked on this amp I don't remember the exact value, but I do remember that it was miniscule.

I believe the mute pin is just fed through the board into a plain unclad hole, so it is not connected at all.

Thanks for your responses!

Well, ther you go...the mute of the LM4780 needs a few milliamps to turn the amplifier on...see the product PDF.

sangram · 11th June 2007, 11:14 AM

On that particular board (at least the Peter Daniel version) there are two pads that look like surface mount pads on the 'copper' side of the board, where I solderded the mute resistor. It's not marked on the silkscreen, so it's easy to miss.

zei · 13th June 2007, 08:56 AM

I did the same mistake
ie, i did not solder the MUTE resistor and i got no sound.

So follow sangram,s suggestion and you will have music in no time

/Z

3rd June 2007, 02:29 AM	#1
Jim Karr diyAudio Member Join Date: May 2004 Location: Southwest Michigan	lm4780 problem I've assembled one of BrianGT's LM4780 boards. Turned on the power, no smoke (praise the Lord). No signal from the speakers, just a very infinitesimally small hum. Apparently it's in protection of some sort. I don't know what voltages and other measurements I should be getting on each pin out. Anyone have any ideas? No solder bridges, and I've checked my connections several times. It all looks correct. Help? __________________ As for me and my household, we shall serve the Lord. Joshua

8th June 2007, 10:18 PM	#4
Jim Karr diyAudio Member Join Date: May 2004 Location: Southwest Michigan	DC voltage is almost nonexistent. It's been so long since I worked on this amp I don't remember the exact value, but I do remember that it was miniscule. I believe the mute pin is just fed through the board into a plain unclad hole, so it is not connected at all. Thanks for your responses! __________________ As for me and my household, we shall serve the Lord. Joshua

13th June 2007, 08:56 AM	#7
zei diyAudio Member Join Date: Feb 2005 Location: Gothenburg, Sweden	I did the same mistake ie, i did not solder the MUTE resistor and i got no sound. So follow sangram,s suggestion and you will have music in no time /Z __________________ Tala är tiga, silver är guld

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3rd June 2007, 06:32 AM	#2
YFW Account Disabled Join Date: Jun 2007	Please check the output DC voltage which should be very low if everything is in normal condition.

11th June 2007, 11:14 AM	#6
sangram diyAudio Member Join Date: Sep 2002 Location: India	On that particular board (at least the Peter Daniel version) there are two pads that look like surface mount pads on the 'copper' side of the board, where I solderded the mute resistor. It's not marked on the silkscreen, so it's easy to miss.

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