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Old 21st March 2010, 11:45 PM   #251
paulb is offline paulb  Canada
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Quote:
Originally Posted by 6h5c View Post
A small suggestion: check if the RESET pins become high, +3.3V. If somehow things around U6 don't work correctly, the DAC remains in RESET state and there's no output either.

Ray
That's a good suggestion. The RESET output should be high (3.3V) under normal operation. It goes low (0V) for about 200 ms when power is first applied.
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Old 22nd March 2010, 04:00 PM   #252
PJN is offline PJN  United States
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Ok thanks guys, I'll check the voltage of the reset pin 14 against ground to see what it reads when I get home tonite.
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Old 23rd March 2010, 12:29 AM   #253
PJN is offline PJN  United States
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Hi guys,

I tooks some readings tonight with a digital source hooked up and running to the EZDAC. the PIC below shows what I got. The reset voltage was on spec. Do you think that its something upstream that's at fault ?

Thanks

PJN
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File Type: jpg DAC readings.jpg (86.2 KB, 203 views)
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Old 23rd March 2010, 01:25 AM   #254
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I got most of my dac assembled in a Lansing case.

Click the image to open in full size.

Hopefully nearing completion, I've got to wire in IEC inlet and wire up the power, switch, mount the ezdual, etc...

At least I can attempt to test it now.
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Old 23rd March 2010, 06:50 PM   #255
6h5c is offline 6h5c  Netherlands
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Quote:
Originally Posted by PJN View Post
Hi guys,

I tooks some readings tonight with a digital source hooked up and running to the EZDAC. the PIC below shows what I got. The reset voltage was on spec. Do you think that its something upstream that's at fault ?

Thanks

PJN
Most voltages look o.k., only Vcom at pin 22 is not correct. This should be 2.25V, just like the other channel. I suspect you skipped a pin writing down the voltages. I don't know what REF at pin 20 should be. If you check and still find it's 2.25V, I suspect a short to Vcc could be the problem.

Ray
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Old 24th March 2010, 01:50 AM   #256
PJN is offline PJN  United States
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Hi Ray,

You were right, I rechecked pin 22 on the dac chip and got 2.25v. Those legs are really close together and I must have hit the Vcc. I took a set of readings on both the AD1896 and the CS8416 and have attached them below.

PJN
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File Type: jpg AD1896.jpg (148.8 KB, 175 views)
File Type: jpg CS8416.jpg (147.2 KB, 173 views)
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Old 24th March 2010, 07:28 PM   #257
6h5c is offline 6h5c  Netherlands
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Pin 12 of the CS8416 is supposed to be 3.3V, it's tied to Vd. Maybe a bad solder joint? Same goes for pin 10 of the ASRC, and pin 9 should be 0V (tied to GND).

Ray
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Old 24th March 2010, 08:07 PM   #258
PJN is offline PJN  United States
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Thanks for the input Ray, I'll double check everything tonight.
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Old 25th March 2010, 02:13 AM   #259
PJN is offline PJN  United States
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Hi Ray,

I double checked things tonite, on the CS8416 pin 12 was 3.3v, and on the ASRC pin 9 was 0v and pin 10 was 3.3. Those damn pins are so tiny and numerous that I find it easy to get lost.

I checked the clock pin 4 (Vdd) 0.77v and pin 3 (out) was 0.92v

I checked U4 and U5 also, the results are in the pic. I noticed that even though I had inputs and voltages on pin 6 (Vr/Vl) I had no reading on either. I used the LME49710MA which was the alt on the BOM. I checked the legs carefully for shorts and bad solder joints but all looked good. Do you think I got a couple of bad chips ?

PJN
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Old 25th March 2010, 08:35 AM   #260
6h5c is offline 6h5c  Netherlands
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The readings on U4 and U5 are o.k. The opamp only amplifies the difference between it's inputs, so it's normal that you don't have any output on pin 6, since both 2 and 3 read the same.

But the clock voltages are not o.k. Pin 4 Vdd should read 3.3V and this may be the error that is keeping your ezDAC from singing! Without supply voltage, the oscillator won't do anything and there's no clock for the DAC. There's an SMD ferrite bead on the back of the board (F2) that transports Vdd to the oscillator, maybe it has a bad connection?

Regards,

Ray
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