CS4397 dac

Quote:

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Originally Posted by iihay

Yep, rhs pad gone. I'm not the greatest with schematics but try me, I can always ask questions!
By the way I suspect the leg of the cap on C34 was touching the cap next to it. I wonder if this was the cause of the higher voltage. All the resistors seem fine.
Appreciate your help, not really wanting to scrap this, would rather keep the pennies for a buffalo at some point.

Iain

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Hmm, ok, I'll try and edit the picture of original board to see if it helps;)
First we'll sort the pad problem then try and figure out the DC offset, BTW this is part of the op-amps non inverted input so if its shorted out you'll get an inbalance

Cheers Leo, don't kill yourself posting anything up now. I've had too much wine to go near a soldering iron tonight ;)

Iain

Too late, well for later see if this makes sense;)

http://i273.photobucket.com/albums/j...soms/dac11.jpg

http://i273.photobucket.com/albums/j...soms/dac22.jpg

http://i273.photobucket.com/albums/j...soms/dac33.jpg

This is presuming the board is same as mine:)
BTW the part numbers on the schematic are not quite right for the op-amp pins so to help try and save confusion I've drawn the pics.

One side of C34 goes from R11 to non inverted input of op-amp, the other side of C34 goes to ground.

If track is broken you can wire R11 to pin3 non inverted input (make sure correct end of that resistor is connected) , solder one end of the broken off C34 from R11 and the other end to C36 which goes to ground

Thanks Leo, great pictures. No cont between pin 3 and R111 so full repair done BUT in the process I managed to break the other pad on C36 Doh! I had a Wima bypass cap at that point (think it was a recommendation from diyaudio) and I knocked it and it was enough to lift the pad.

Really annoyed with myself, is there a fix for this, link to R10 and R15 from wayward end of bypass cap?? (towards opamp end of board). The modified pad is still in place.

Up until yesterday this board looked really nice!

Iain

Drawn on where C36 is connected to, right side (near C17) goes to ground.
Other side of C36 goes to R15 and R10

http://i273.photobucket.com/albums/j...soms/dac44.jpg

Fix done, bit of a lash-up but all back to how it was. Negligable mv on the left output. 1.4V on the right.

Iain

What voltages do you get on op-amp from

pin2 to ground?
pin3 to ground?

pin5 to ground?
pin6 to ground?

Quote:

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Originally Posted by leo

What voltages do you get on op-amp from

pin2 to ground?
pin3 to ground?

pin5 to ground?
pin6 to ground?

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1 -8mv
2 1.42V
3 1.42V
4 -12V
5 1.42V
6 1.42V
7 1.42V
8 12V

Iain

ps. Sorry for delayed reply, been busy eating chocolate :)

you got a bad track ,joint or resistor I reckon

Look at the voltage reading of the differential out of the dac , + is 1.4v, - is 1.4v
Differential to line out this should give 0v

A clue, whats the DC offset out of that dodgy channel? you got one half missing;)

Don't go making yourself into a bloater with all that choccy :lol: