Yuhang and Marc and Matteo

We found DDS boards made sound last week. Then we tried many different combinations of inserting and removing different DDS boards, but the sound remains.

Then what happened was that we started to check the voltage provided by the NIM rack. We found the drop of voltage when a certain DDS board is inserted. The details of which caused which (whether 6V or 12V) were not recorded. And we found some very strange values. So we stopped at that time.

After that, we tried to figure out where the problem is from. Is the problem from DDS board, or NIM rack, or 500MHz oscillator?

To check if the problem is from NIM rack, we tried to insert DDS boards and oscillator to another NIM rack or a new NIM rack. 

We found that 

1. When we insert DDS board separately to the NIM rack holding PLL boards, DDS board didn't make sound.

2. When we insert more than two DDS boards (or DDS with oscillator) to a new NIM rack, NIM rack starts to make sound.

Then we confirm the problem is from DDS or oscillator. In particular, we found that the oscillator doesn't provide 500MHz signal any more.

Now, the DDS system is left in TAMA with the problem not figured out yet.