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Old 1st March 2005, 05:54 AM   #1
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Default BrianGT's LM3886 Kit

Got the kit, and everything is great, until I went to put it together.

Which Resistor is which? R1, R2, R3, etc mean nothing without something to tel me which is which!
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Old 1st March 2005, 05:58 AM   #2
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Default Re: BrianGT's LM3886 Kit

Quote:
Originally posted by scott_jcp
Which Resistor is which? R1, R2, R3, etc mean nothing without something to tel me which is which!
You could try Brian's web site...

Or try a forum search...
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Old 1st March 2005, 06:06 AM   #3
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I spent about an hour doing that actually.
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Old 1st March 2005, 06:10 AM   #4
BrianGT is offline BrianGT  United States
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Default Re: BrianGT's LM3886 Kit

Quote:
Originally posted by scott_jcp
Got the kit, and everything is great, until I went to put it together.

Which Resistor is which? R1, R2, R3, etc mean nothing without something to tel me which is which!
Components:

Board pic:
http://www.briangt.com/gallery/lm388...886_019?full=1

Amp board:
R1 - input resistor = 1k (2 - black on the resistors packed)
R2 and Rf - input-to-ground resistor = 22.1k (4 - uncolored)
R3 - feedback-to-ground resistor = 681 (2 - blue)
Rm - mute resistor = 10k (2 - red)
picture of 2 ways to wire feedback resistor:
http://www.briangt.com/gallery/lm3886amp/3886_037
with and without the feedback capacitor, notice the resistor placement
C1,C2,Cm - 100uf
C3,C4,Cz - 0.1uf
Ci - 47uf

Power supply board:
R1,R2 - 1 ohm resistors for snubber network
R3,R4 - 2.2k bleeder resistors for power supply caps (mount on bottom)
R5 - 10k or 22k resistor for LED (10k might be too bright, so try 22k to lower the current supplying the LED to reduce brightness)
C1-C4 - snubber caps = 0.1uf
C5,C6 - power supply caps = 10,000uf
C7 - 10uf cap for LED (extra included in bag with diodes)
D1-D8 - power supply diodes = MUR860

I am working on a manual now, and will try to finish it soon.

--
Brian
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Old 1st March 2005, 06:11 AM   #5
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Thank you so much!
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Old 2nd March 2005, 03:56 PM   #6
troystg is offline troystg  United States
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Default Re: BrianGT's LM3886 Kit

Quote:
Originally posted by scott_jcp
Got the kit, and everything is great, until I went to put it together.

Which Resistor is which? R1, R2, R3, etc mean nothing without something to tel me which is which!

Thanks Brian for the post! I was going to ask the exact same question but found this post in the search. Remarkable timing on Scott's part! May I suggest you post the color code on your web page?



Scott-

Rchdn TX... I'm up in McKinney. Want to meet up for amp listening sessions one day?

Thanks,

Troy
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Old 3rd March 2005, 12:21 AM   #7
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It is a good idea to have a multi meter if you are building amps. Even a $20 one from radio shack will do fine. At the very least, it is good to know if it safe to plug your speakers in. That said, resistors are easily measured.

-d
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Old 3rd March 2005, 01:08 AM   #8
troystg is offline troystg  United States
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Quote:
Originally posted by dsavitsk
It is a good idea to have a multi meter if you are building amps. Even a $20 one from radio shack will do fine. At the very least, it is good to know if it safe to plug your speakers in. That said, resistors are easily measured.

-d

Only Brian knows the color coding of the resistors he shipped. (I assume he has a master plan with the markers ).

The resistors he shipped are NOT the factory spec'ed values so proper placement is a guesstimate until he confirms. (Which he did).

I think Scott's original post was directed towards Brian even though he does not state so.

PS, I have an ORIGINAL Fluke 87 and the 10k probe I bought myself for graduation back in '87. I use it at LEAST every other day and it's still in "close to mint" condition.
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Old 4th March 2005, 12:36 AM   #9
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Look at the pictures posted for the power supply. Gold stripe with 3 red stripes go on the bottom (R3 and R4). Black stripe with 2 gold stripes goes on the top (R1 and R2). My guess on the led is longer leg goes where arrow is pointing marked on board. On the led resistors they are so small even with my magnifying glass I can't read them. I see though that on has a red tab and the other does not so this must mean something. Any corrections anyone.


Cheers,
Pete
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Old 4th March 2005, 02:41 AM   #10
troystg is offline troystg  United States
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Hi budwiser-

Thanks for the post, but Brian already got us straightened out..

He is EXCELLENT on support and his kits aren't half bad either .

I would recommend his kits to anyone, newbie or experienced, to try for ease of assembly and excellent sound.
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