Problem- THG Stability in Coherent 355-1500

[icampbell2011]

We recently purchased a machining tool with an older Coherent 355-1500 laser. There are some problems:

Cold start: there is a Fault 30 SHG Battery error, that shouldn't be to hard to fix. Clear that error and SHG and THG temps rise and stabilize just fine. Turn on the diodes (90%) PRF=10-15Khz. Turn on Pulses and the THG temp will rise from 58.06 to 58.88, then start to fall. The problem is it doesn't stop, it just keeps dropping until Fault 7 shuts the laser down. The correct the trouble is to turn on and off power supply, then THG temp will rise and stabilize normally, until you start pulses again. This cycle takes about 5 minutes. The previous owners had the same issue back in 2007. They were trying to figure it out when the system was moth balled. This is an old laser, no longer supported by Coherent. Any ideas? I need to change the desiccant in the laser head, but i don't believe that has anything to do with it. I have tried varying PRF and Diode power. I can't keep the laser on long enough to optimize any temperatures. TT=2120. Diodes have about 6,000 hours. crystal has 4 used positions. I tried different positions 5 and 22 and back to 10.
Ian