single-supply LM3875 design not working :(

[strykerhorse]

Good morning, everyone---

I've designed two versions of a single-supply powered 3875TF setup, and have had no luck getting the chip to output sound.

The power supply outputs a DC voltage when AC is applied to it, with little if any AC at the outputs (haven't looked at the signal with a scope though, so take that as you wish).

Here is a picture of the reference design for a single-supply setup:



I've used this same setup with two exceptions:

-didn't use any of the optional/starred parts
-I used a 56k resistor in place of the 75k resistor because I had one around

Cap values are as stated in the reference design, with a Cs value of 100uF

Here are a few pics of my implementation, power supply first:







I'd appreciate any help you guys can provide! Thanks again.

[mjf]

hello.
have you left away ci,rsn,csn?
this can cause some problems.
greetings....................

[pacificblue]

Originally posted by strykerhorse
The power supply outputs a DC voltage when AC is applied to it,

How much DC? The LM3875 needs > 20 V single supply.

Could you post photos, where the important parts are not hidden in the shade? And maybe a bottom view as well to see, if all connections are in the right place?

[strykerhorse]

Originally posted by pacificblue

How much DC? The LM3875 needs > 20 V single supply.

I'm giving it ~45V DC. I'll get more pics up for you momentarily....

[bbp]

check pin 1 and 4, there is a voltage = your PSU
check pin 7, pin 8 , pin 3half voltage of PSU