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Old 17th May 2012, 11:21 AM   #11
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Quote:
Originally Posted by basi View Post
Greetings! C4 is same as C6 47uf,probably is better to put there 100-220uf.You must put C2 22uf,C7 0.1uf and R6 jumper or 10 ohm resistor and that should work.
Your explanation of R6 answers my most recent posted question.

C4 is shown (next to the V+ pad) as round and polarized on the board but the supplied part is square and unpolarized.

Can you explain what the other optional components are for, C1, C2, C7, R1 (listed as optional and not used), and R5?
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Old 17th May 2012, 11:24 AM   #12
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Originally Posted by AndrewT View Post
Why so many components omitted from the PCB?

If I was going to test drive a car. I damn well would be sure before I set off that the steering wheel was not omitted.
Some of those were listed as optional without any explanation of what they were for or when you might want to use them. Others were described ambiguously, e.g "R1 not used (optional..)
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Old 17th May 2012, 11:31 AM   #13
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Hi Mark.

The R6 jumper is mentioned here, well spotted basi.

Finally made a LM1875 amp

John
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Old 17th May 2012, 12:18 PM   #14
basi is online now basi  Croatia
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Quote:
Originally Posted by mbohn View Post
Your explanation of R6 answers my most recent posted question.

C4 is shown (next to the V+ pad) as round and polarized on the board but the supplied part is square and unpolarized.

Can you explain what the other optional components are for, C1, C2, C7, R1 (listed as optional and not used), and R5?
Hello again!C4 must be Elko same as C6 your's supplied part is mistake.
C1,C2,C7 and R5 are good values there's no need for 'optional'.
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Old 19th May 2012, 02:45 PM   #15
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The heatsink pictured in post #6 will cause failures in at least two ways:
It is far too small, and that is a mistake because LM1875 are easily damaged by heat (explode).
It is not insulated, and that is a mistake because the tab of LM1875 has voltage and will explode unless you install insulator pad, thermal paste, and shoulder washer to block voltage properly.

There are two errors that may cause infinite gain (explode): R6 is not optional. It can be from 0 ohms (wire) to 10 ohms. I use 2 ohms.
C2 is not optional. If either R6 or C2 is omitted, the amplifier explodes. Why does a kit have so many documented options for explode?

Other errors:
If C2 is too small, it will omit the bass (sounds like loud mids) and thus should be at least 100uF or more.

If R6 is shorted, the amplifier might hum, so use a resistor, not a wire.

R1 should be approximately 100pF capacitor parallel with a 1M resistor.

R2 should probably be 10K.

If you want a mids-n-treble amp, 47uF for C4 and C6 can work okay to get the midrange especially loud (implying also using a subwoofer). Most people won't like that. SO, for full bandwidth amp, C4 and C6 should both be 220uF or more, and you can fit good size caps on that board if you solder the little gray box caps trackside.
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Last edited by danielwritesbac; 19th May 2012 at 02:48 PM.
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