BrianGT's LM3886 Kit

[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!

[jeff mai]

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...

[scott_jcp]

I spent about an hour doing that actually.

[BrianGT]

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

[scott_jcp]

Thank you so much!

[troystg]

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

[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

[troystg]

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.

[budwiser]

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

[troystg]

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.