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Alien DAC v1.1 Construction Thread - Page 46

post #676 of 1560
4/16/07 at 4:42am
Fair point, but working between the two had me scratching my head after a few more hours of troubleshooting.

The previous post questioned whether I had the pins correct. I wrote the initial post after spending many hours staring at the schematic and the DMM. I have double - and triple - checked and I do have 4.9V on the inputs and mV on the outputs.
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post #677 of 1560
4/16/07 at 4:47am
I'll post a photo shortly, but the chip says BB REG 101UA
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post #678 of 1560
4/16/07 at 6:53am
Have you tried it with a slightly higher input voltage ?

IIRC, input voltage is meant to be something like 300mV higher than Vout.

Don't quote me on that, I'd look at the datasheet.
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post #679 of 1560
4/16/07 at 9:17am
I tried it on my other computer with PS voltage of 5.14. No joy - similar voltages.

I'm currently going back through all the joints and checking and redoing them. Nothing so far.
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post #680 of 1560
4/16/07 at 1:17pm
Checked that you have R31, R32 and C32 all in the right spots and not mixed them up ?

Maybe it's stuffed ?
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post #681 of 1560
4/16/07 at 2:28pm
It isn't the input voltage.


My guess is you either have a short between +5 and ground (most likely on the 2702) or one of the parts in the regulator isn't soldered. Check for shorts then reflow the solder on the REG101.
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post #682 of 1560
4/17/07 at 4:27am
I've triple checked R31 (bottom of the board, 31.6K), R32 (top of the board, 11.5K) and C32 (bottom of the board).

I'm thinking maybe it is stuffed But I'll stay on it for a few more days.


Quote:
Originally Posted by splaz View Post
Checked that you have R31, R32 and C32 all in the right spots and not mixed them up ?

Maybe it's stuffed ?
I took the REG101 off the board and found the input voltages the same and nothing on the output (as expected).

Given that the vast majority of problems here seem to be with the 2702, I am resigned to the fact that this is the most likely cause of my problems. I will plug away for a few more days in the vain hope that I can find the problem with the 2702, but I'm losing faith... fast
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post #683 of 1560
4/17/07 at 5:52am
x2 on the shorted-to-ground. Check for continuity between the 5v test point and ground. One tiny bridge on the PCM2702 will do that.
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post #684 of 1560
4/19/07 at 1:20am
Might some CAD files of the PCB layout be available? I've been looking all over the place for some plans to make a PCB from, but I haven't been able to find anything. If someone could link me to an EAGLE CAD file or something, I'd really appreciate it.
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post #685 of 1560
4/19/07 at 5:10am
Sorted the 5V issue - presumably a solder bridge.

I have spent quite a bit of going over the pins on the PCM2702 with desolder braid, which seems to have fixed the 5V but I now am getting an unrecognized device error in Windows. By all accounts this is still most likely a solder bridge on the chip... sigh... I'll continue tonight.
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post #686 of 1560
4/19/07 at 5:35am
Quote:
Originally Posted by fordgtlover View Post
I have spent quite a bit of going over the pins on the PCM2702 with desolder braid, which seems to have fixed the 5V but I now am getting an unrecognized device error in Windows. By all accounts this is still most likely a solder bridge on the chip... sigh... I'll continue tonight.
Keep at it!

The 5V side of the chip is the "analog" side; the 3.3V side is the "digital" side. So if there's a problem with the computer recognising the chip, then I'd check the 3.3V side.
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post #687 of 1560
4/19/07 at 8:28am
Better late than never... here is mine.
Now ready to be cased.




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post #688 of 1560
4/19/07 at 8:35am
Good grief, Amb! It looks robotically built - no defects at all, not even a slightly turned resistor here and there.
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post #689 of 1560
4/19/07 at 8:54am
Quote:
Originally Posted by tomb View Post
Good grief, Amb! It looks robotically built - no defects at all, not even a slightly turned resistor here and there.
Thanks, yeah, I am obsessive when it comes to the little details. Btw, the soldering is all done with a lowly Weller WSC-100 station with a ST-6 tip. Proof that you don't need a mega-buck iron to do a good job. I gotta say, though, working on this board was not kind to my tired eyes, even with 3.0 diopter clip-on glasses...
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post #690 of 1560
4/19/07 at 9:14am
Quote:
Originally Posted by amb View Post
Btw, the soldering is all done with a lowly Weller WSC-100 station with a ST-6 tip.
wow --
From the photo, I assumed you borrowed a pick and place machine from work.
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