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Chip Amps Amplifiers based on integrated circuits

My_Ref Fremen Edition - Build thread and tutorial
My_Ref Fremen Edition - Build thread and tutorial
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Old 19th March 2019, 09:38 AM   #4111
lokason is offline lokason
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Join Date: Mar 2016
Hello,


I've a stupid question. My two lm3886 are on the same heatsink and not in a metal box.
Should I link the two HSGND to the heatsink or just one ?


Another stupid question, I've mounted the BD139-16 in the same orientation on the two board ( and noticed it when measuring the voltage... >.< ) is it possible that I fried something behind ?


Grim,
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Old 20th March 2019, 02:59 AM   #4112
Panelhead is offline Panelhead
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I would connect this ground to both boards.
Not sure what you did with the BD-139-16. Is one installed incorrectly? Try flipping it around to see if everything works okay.
If anything was damaged, hopefully if is just the one transistor.
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Old 20th March 2019, 01:09 PM   #4113
lehmanhill is offline lehmanhill  United States
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Try Panelhead's suggestion first, but if that doesn't solve it, please tell us what voltages you have on both boards. Also, does the relay click?

The BD-139-16 is in the voltage regulator for the opamp. It is easy to fry. I have burn out theses transistors by accidentally shorting two pins with my voltage meter probe.

Jac
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Old 24th March 2019, 02:24 PM   #4114
lokason is offline lokason
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Hi, the relay click.

I've put the BD-139-16 in the right direction,
Now, when i measure the voltage in output, with the input shorten : it's ok.
With nothing on the input, it's unstable :

20190324_124116.mp4 - Google Drive

Some picture of the board :
P1000699.JPG - Google Drive
P1000703.JPG - Google Drive
P1000700.JPG - Google Drive
P1000702.JPG - Google Drive

NB : i've a hum when i plugged a speacker with nothing in input.
it's still here with a potentiometer in input when the level is not anymore @0
Measuring the + input give me unstable value like in output.

About the part 11 FIRST POWER UP " the value are a little lower ( like 14V instead of 14.6V)


grim,
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Old 24th March 2019, 08:42 PM   #4115
Panelhead is offline Panelhead
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You should not have to short the input. But shorting the input will lower the noise.
If shorting the input gives single digit dc offset everything is working. Plus your relay is closing, another good sign.
If the relay is open you will measure very low dc voltage on the output.
I have measured many versions of My_Ref with the input open. All had low level dc offset.
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Old 25th March 2019, 09:24 PM   #4116
lokason is offline lokason
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My bad,... i was using a 100Kohm alp... It's clearly better with a 50kohm... ^^' no more hum in the speaker \o/ ( i'll see to use a 10k if i found one like the 100k and the 50k )



Thank you lehmanhill Panelhead and ClaveFremen
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Old 26th March 2019, 02:28 AM   #4117
Panelhead is offline Panelhead
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Yes, use a 10K. If your source can handle lower, go lower.
Better still a preamp or source with digital volume control.
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Old 30th March 2019, 05:56 PM   #4118
mpeck is offline mpeck  France
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Location: France
Hello all,

I finished to assembling two PCB rev 1.7.

Everything was fine until I connected the input: I heard a loud "poc" on one of my speakers. After inspection, I forgot to connect the PGND on one PCB . This is what happens when you work late at night on your DIY projects!

Since then, the relay no longer activates on the PCB where the connection has been forgotten and the LM3886 is now hot.

I checked the voltages indicated on the PCB and found nothing wrong.

I have already replaced LM318, D1, D2, D2, D3 and LM3886 without success. I measure a DC voltage of -34V on the LM3886 output.

Do you have any suggestions for troubleshooting?
The positive side is that the second PCB is functional...

Thank you for your help!
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Old 30th March 2019, 06:03 PM   #4119
Mark Whitney is online now Mark Whitney  Netherlands
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Check R11.
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Regards Mark.
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Old 30th March 2019, 07:08 PM   #4120
Joseph K is offline Joseph K  Hungary
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Yes wanted to say the same
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