| 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?:hot: |
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| YFW |
| Please check the output DC voltage which should be very low if everything is in normal condition. |
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| jackinnj |
| 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?:hot: |
How have you connected the MUTE pin? |
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| 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! |
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| jackinnj |
| 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. |
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| sangram |
| 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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| zei |
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 |
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