Peter, Fil, Jason, TJ, TVo

We started the day thinking the laser head could be the issue, but once we swapped the cables and plumbing to a brand new laser, it didn't solve our problem of not being able to lase.  Peter found that if he wiggled and loosened an RF cable that goes from the Sine-to-Square wave comparator box to the 4-way splitter box, then we start to actually lase intermittently.  This confused us for a while and we decided to inject our own square wave with a function generator and bypass the comparator box, with 0-5V peak to peak @ 40.68 MHz and it started lasing at 55 Watts.  Then we added the comparator box and it still worked using our own source. 

This lead us further upstream towards the RF distribution box D1000124 and found that there was a bad cable.  The comparator box is expecting at least 4-5 volts peak to peak but was only getting approximately 40mV.  This fooled us because it looked like a decently shaped RF signal and we thought it was OK, but the power was all wrong.  Once we replaced the cable, it worked pretty well.

Tomorrow we'll replace the plumbing and cabling to make sure the old laser and old RF driver still works and return the spare laser and RF driver to storage, so we're not fully out of the woodwork but I think we found a big missing puzzle piece and we have at least one laser that works.  Not sure why this cable went bad all of a sudden.