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Old 9th September 2008, 08:17 PM   #1
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Default I had problems with my LM4780


I have used boards from Peter Daniel, but parts and Integrated circuit did not came from Peter.

I have assembled and no error, received double check, no shorts or wrong parts.... transistor insulated, and even side screws have no metal to touch into the Integrated circuit.

Was powered using 35 plus 35 volts supply, 3300uf each rail for condensers, speakers impedance 8 ohms.

Since the first moment i had full positive rail voltage into the "B" channel...the other channel operated normally but the temperature was too much big.... sometimes reached 80 degrées celsius into the plastic cover..the black cover (gray)... i suppose heatsink had a bigger temperature, was not measured... thermal protection have not entered into operation.

Them i decide to reduce voltage, and the unit goes operating using 17.5 volts plus 17.5 volts (datasheet said more than 10 plus 10 volts)... operated warm and sound was great...much better than 35 plus 35 volts.

Well...the rigth channel damage was creating problems, i could not switch off positive and negative supply from the rigth channel to let the unit work in peace.

Finally, what was obvious happens, the integrated circuit started to have off set floatings.... sometimes speaker jumped forward and then jumped backwards... fuse was 5 amperes and the unit was sending less than that... my speakers (2 units, 4 ohms each, 150 watts each) can hold the DC power on them without problems if less than 30 seconds.

I have made a video showing you what happened..... the chip is dead...buried and will not produce problems to me anymore.... there's another youtube video into "Dx Amplifier" that shows the unit operating yesterday...of course..when already alive.

Visit youtube to understand what happened:

http://www.youtube.com/watch?v=PtlR7qGu3xk

regards,

Carlos
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Old 9th September 2008, 08:23 PM   #2
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Default Here is the chip.... was installed inside the supply case


The heatsink was between the transformer and the chip board.... the integrated circuit was insulated...no electrical contact with the heatsink or other chassis part.

regards,

Carlos
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Old 9th September 2008, 08:25 PM   #3
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Default What do you think... was bad luck?....


Are there fake units alike this one? (LM4780)

regards,

Carlos
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Old 9th September 2008, 08:29 PM   #4
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Default Here... the sound when operating


http://www.youtube.com/watch?v=e6gZljMEazg

regards,

Carlos
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Old 14th September 2008, 09:23 PM   #5
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Default I have built the LM4701T amplifier too


Dislike the over current and over voltage protection...produces noises.

Here you have one video about this chip... there are others, type Dx Amplifier and others will appear, also this chip playing music.

http://www.youtube.com/watch?v=pLNCR2X57bw

regards,

Carlos
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Old 15th September 2008, 04:48 PM   #6
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Default I have assembled the fouth LM4701T


The second one burned with i was fliping a switch.

http://www.youtube.com/watch?v=F5tr4gHsNkU

regards,

Carlos
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Old 15th September 2008, 06:35 PM   #7
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Old 15th September 2008, 10:38 PM   #8
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Default hehehe.... i usually do not understand those smilies


...what they mean.... but seems may be something good.

Thanks

regards,

Carlos
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Old 16th September 2008, 01:48 AM   #9
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Great stuff!
I approve of your taste in tunes - Stevie Ray's Tin Pan Alley on your sonic voyage
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Old 16th September 2008, 11:56 AM   #10
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Default Your kindness is what deserves approval my dear friend


Be happy into beautifull Canadá

regards,

Carlos
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