Search found 124 matches

by AllenWallace
Fri Nov 15, 2013 1:57 pm
Forum: High Voltage - Fusor Input Power (& FAQs)
Topic: Minimum Voltage for a Demo Fusor
Replies: 8
Views: 3096

Re: Minimum Voltage for a Demo Fusor

I have seen star mode with a flyback transformer. it was not very bright, but distinct. You don't need very much voltage for plasma. I'd recommend a NST (neon sigh transformer) for a demo fusor. Your comment about putting 2 MOTs in series concerns me, do you understand the break-down voltage problem...
by AllenWallace
Sun Nov 10, 2013 7:24 pm
Forum: Vacuum Technology (& FAQs)
Topic: dirt simple turbo pump controller?
Replies: 5
Views: 2853

Re: dirt simple turbo pump controller?

This is all great advice! My unit is a Phieffer TPU-050 with four drive coils. Normally a pair of Hall effect sensors determine which coil to energize next, however my sensors are defective.
by AllenWallace
Sat Nov 09, 2013 3:36 am
Forum: Vacuum Technology (& FAQs)
Topic: dirt simple turbo pump controller?
Replies: 5
Views: 2853

dirt simple turbo pump controller?

What would happen if one drove a turbo pump like a stepping motor? With no feedback from any motor position sensors? You would have to ramp it up slowly at first, just like a stepping motor, and you couldn't get really high rpm. I'm looking to get from , say, 50 millitorr down to 1 millitorr. Nothin...
by AllenWallace
Mon Nov 04, 2013 5:34 am
Forum: Vacuum Technology (& FAQs)
Topic: Any advice on a bad turbo pump Hall effect sensor?
Replies: 2
Views: 1385

Re: Any advice on a bad turbo pump Hall effect sensor?

The pump controller Is a TCP040. The compatibility matrix I've seen indicates that it would also work with the TCP120/121.
I don't see 4-wire hall effect sensors from Digikey... I suppose I'll have to order from Pfeiffer.
by AllenWallace
Sun Nov 03, 2013 1:58 am
Forum: Vacuum Technology (& FAQs)
Topic: Any advice on a bad turbo pump Hall effect sensor?
Replies: 2
Views: 1385

Any advice on a bad turbo pump Hall effect sensor?

My Pfeiffer TPU 050 turbo pump appears to have a bad Hall effect sensor. These pumps use a pair of sensors that drive the pump motor windings in a 1-2-3-4 sequence. These sensors are powered by a 40ma constant current supply, and each sensor has two outputs with a 300 mV signal. When one output goes...
by AllenWallace
Thu Aug 22, 2013 3:47 am
Forum: Vacuum Technology (& FAQs)
Topic: Turbo pump oil lubercation
Replies: 1
Views: 988

Turbo pump oil lubercation

I've dusted off my Pfieffer TPH 060 turbo pump after 10 years of storage. The manual says to replace the oil impregnated felt reservoir every two years, so I'm quite over-due. Has anyone had experience with this? Can I simple re-oil the felt? Wheres a good place to buy this? It's not in the LDS or D...
by AllenWallace
Thu Aug 22, 2013 3:35 am
Forum: Fusor Construction & Operation (& FAQs)
Topic: non-permanent sealing of screws
Replies: 5
Views: 2221

Re: non-permanent sealing of screws

This is a follow-up to sealing screws... Using just vacuum grease didn't work at all. The vacuum just ran through the threads. I could even feel the vacuum pull with my finger on the vacuum wall exterior. I ended using Teflon tape with the 8-32 crews. The chamber was professional leaked detected and...
by AllenWallace
Fri Jul 12, 2013 3:41 pm
Forum: Fusor Construction & Operation (& FAQs)
Topic: non-permanent sealing of screws
Replies: 5
Views: 2221

non-permanent sealing of screws

I need to put several low voltage feed-throughs in my vacuum chamber, which is a modified bell jar design. These capacitor-style feedthroughs use a 8-32 thread and I've drilled and tapped the chamber. I can epoxy these in, but I rather not in case I have to replace one. Does anyone have any suggesti...
by AllenWallace
Sat May 25, 2013 4:33 am
Forum: Fusor Construction & Operation (& FAQs)
Topic: Building a Fusor at 12 Years Old
Replies: 18
Views: 6571

Re: Building a Fusor at 12 Years Old

>Your idea is good, but if the pressure vessel is glass bottles, glass bottles are likely to split. I don't agree. Using a wide mouth canning jar is an excellent vacuum chamber for a small demo fusor and other small vacuum experiments. They are designed for vacuum service, or at least down to 17 tor...
by AllenWallace
Tue May 21, 2013 1:45 am
Forum: High Voltage - Fusor Input Power (& FAQs)
Topic: Need help to review the circuit schematics
Replies: 9
Views: 3301

Re: Need help to review the circuit schematics

Yes. anti-parallel is what I wanted to say. Richard's recommendation on a wire-wound shunt is also good.