Turbo Pump Problem

• Prep chamber turbo did not pump down. Stalled at a few thousand RPM, ~ 40 Watts, bearings started to heat. Weird noise. Possibly scroll pump did not start. Foreline pressure gauge showed ATM. Airlock pressure ~ 25 Torr.
• Cycled power on pump. Now system goes to full speed eventually, but power stays at 66 W instead of dropping to 12-18 W. Foreline still showed ATM.
• Swapped scroll pumps for nano and prep. Start pumps together. Now both start normally, foreline pressures 0.13 mBarr prep (with nano scroll), 0.19  nano (with prep scroll). Both turbos ~ 15+-3 W, normal. Ultimate foreline pressure was ~ 0.055 mBarr, or 0.075 during bake.
• Possibly scroll pumps have trouble, or roughing lines leaking due to sharp bend on hoses. Exchanging scroll pumps seemed to fix problem. need to invert pumps again.

Let turbos run. Both prep and nano running about 10 W next day.

On Friday 10/26 switch scroll pumps back. Now prep turbo is slow to start, eventually reaches 100% with 88 W power. Prep pirani reads "atm". Shut down, disconnect scroll, pull out from rack, clean and reconnect quickflange with no stress on hose. Try again. Better, quick pump down, standby 18 W, foreline 0.10 mbar by pirani

problem was bad foreline pressure, possibly due to leak from strained hose. 

More trouble Nov 8, 2012

• Try to start turbo. Stalls at 63 W 27%. Pirani reads ATM. 
• Vent and retry. Similar results. Airlock shows ~ 10-15 torr.
• Stop again, examine turbo. Remove hose from scroll pump. Near pump the transparent plastic hose looks "misty". Remove hose, moisture condensed on inside ???.
• Reconnect hose, try again. This time system pumps down, foreline pirani indicates rapidly (< 60 s), goes below 0.5 mbar, pump reaches 100%.
• Then power and foreline pressure increase, ~ 40W at 100%, foreline 1.1 to 1.2 to 1.5 to 1.7 mBar over several minutes 
• This is very strange.
• Stop turbo, disconnect foreline, try again. This time 19W at 100%, foreline 0.16 mB and dropping slowly (normal).
• Possibly some water condensed in scroll pump when foreline was leaking, now being slowly pumped away. 
• after one hour foreline 0.12 mB, 17 W