DDS 20 Function Generator Kit

[MeggerMan]

Hi Gregi,
I have both a built board and kits, and yes you are correct, it looks like the warning paper is complete rubbish.
If you look closer at the photo of the top side and the component overlay you will see they are different.
See C24 and C27, they are near the decoupling caps, where in the "real" board layout C27 is next to IC2 and C28.
I only spotted this because I am building an inverter board (+5v to -5V) to solder onto the back side and use the C24 and C27 pads as the connections. I thought, ahh, that's not right.
I think what has happened is that they updated the overlays and component masking on the actual board but forgot to stop sending out the error sheet.  I will email Stephanie on Monday to point this out.

Also I found one kit where the pins on the AD9835 were bridged in two places with solder so if you have a microscope (20x or there abouts), just check the pins over. There was one big clod of solder on two pins (easy to see) and a very fine path(impossible to see by eye and tricky even at 20X mag.) of solder balls on the other two pins.
It was like a row of small marbles lined up across your desk where your desk is the 0.3mm gap!
The resistance showed up as about 0.4 ohms across SCLK and SDATA pins.
Shortly, I will post details at the start of this thread, of the inverter board I am designing.

Regards
Rob

[Gregi]

Thanks MeggerMan.

Now, I looked at the AD9835 chip and I saw some bridging. Could you tell me if it is something normal, or is it a faulty board then?

Greg

[Thedane]

Gregi:

It isn't normal - so you do have a defective board.

You should be able to fix it by removing the shorts. This can be done with a fine braided solder wick.
Just remove the solder and solder it again (The solder wick usually sucks too much solder off) so the pins looks like the correctly soldered ones 

Can anybody confirm that the AD9835/AD9833 chip outputs "noise" when the frequency settings are adjusted?

[Gregi]

Geez man, its just incredible how in the manual they brag about the numerous tests they made on the board to ensure its quality... and how one need to be careful when soldering not to make bridging.... and there you go... they couldn't be precise themselves. 

Well, I'll try to correct this thing then.

Thanks,
Greg

[Thedane]

The board does look like it was done on machines, and sometimes faults happens - this can even happen in large production sizes. 

Was this board one of their "mount it yourself" kits?
If it was, I would advise that you check all the other solderings visually - as it would seem that their solder paste screen holes either are too big, or the screen itself too thick (This deposits more solder paste on the pads = bridging can occur).

I'm currently working on my own function generator based on the AD9833 chip, but unfortunately programming isn't one of my strong abilities at the moment  - but I'm learning 
I seem to recall somebody saying that when you change the frequency parameters the generator outputs some digital noise on the output - has anybody seen this?  (I tried the search function, but found nothing  )