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Registered Member #9711
Joined: Sat Jan 19 2013, 03:27PM
Location:
Posts: 65
As of today, I have the x-ray tube and HVPS up and running except I'm still having HV leakage issues in the following ways:
1) The HVPS, lead shielding, and tube are all located within metal shelving. Unfortunately, I am still getting a slight shock if I touch the shelves when the unit is energized. I continue to use the 40 KV rated TV wire surrounded by a layer of PE tubing.
2) My main desktop PC is located about 7 feet away from the HVPS and tube. As before, the PC still tends to freeze when the unit is in operation, forcing me to reboot to become normal again.
It is obvious that I am still having HV issues. I didn't yet try spark plug wire; would it make a difference over the TV wire slid inside PE tubing, or not? Also, both the contents of the HVPS, which would include low voltage driver power supply, flyback, and multiplier, are housed within a Sterilite plastic storage container. Should I have placed the components into a metal chassis instead? Also, might it help to cover the outside of the PE tubing with aluminum foil tape to help minimize spraying/ arcing?
As I said, the unit is working, but in order to use I am going to have to shut down my desktop each time, plus avoid touching the metal shelving unless I can find ways to correct for this.
Thanks in advance for additional help and suggestions.
Registered Member #4074
Joined: Mon Aug 29 2011, 06:58AM
Location: Australia
Posts: 335
Sounds like you definitely need to ground the metal shelving. From your description, it seems the entire unit, shelving and all, is floating at a voltage other than zero! If the PC is freezing when the unit is turned on, perhaps you have HV or noise making it back onto the mains conductors?
Registered Member #9711
Joined: Sat Jan 19 2013, 03:27PM
Location:
Posts: 65
I covered the entire plastic chassis with aluminum tape, sealed it as best as I could, then grounded everything to ground. While I am now not getting the shocks when I touch the shelving, the PC still freezes, but I'm finding that it happens when either the HV is at the lowest setting and/or the voltage is pulled down by the filament current. Not sure what to make of it, but definitely coming from the high voltage section. When only the low voltage driver section is operating, no matter the adjustment, the PC stays unfrozen.
Registered Member #9711
Joined: Sat Jan 19 2013, 03:27PM
Location:
Posts: 65
Ash Small wrote ...
If the TV lead you are using id old, it will probably be leaky. It's worthy trying a new lead. Can you find any of this locally?
It comes in different colours. It seems the green is cheapest here:
Ok, I have some of that one the way, copper core 7mm size. Now I'm wondering two things: 1) how to couple the spark plug wire to the TV multiplier wire end, assuming I cut off the "cup" and 2) best way to hook the spark plug wire up to the tube. Being a rotating anode tube, it has a 1/4" threaded insert at the connection side. With the current set up, I just made push up contact between tube tube and a "cup" end of a tv multiplier, then siliconed the combination in place. Thoughts?
Registered Member #3414
Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245
If you cam use these, with a bit of silicon grease:
These obviously fit onto the ends of spark plugs, but the bit they fit onto often unscrews from the plug, and could then be screwed onto your contact, assuming you could fix the correct thread to it, or you could probably improvise something with a bit of round bar of the correct diameter and a file.
Other than that, potting the ends in silicon or epoxy, or under oil would probably be the best bet.
You may also want to put some silicon tubing over the 7mm ign cable, maybe in conjunction with silicon grease, but new ign cable should withstand 40kV.
This silicon grease is dirt cheap, and has a claimed dielectric strength of 30kV/mm : Five tubes for £10.30 here.
Registered Member #3414
Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245
Well, the data sheet says it is silicone based, and it's recommended for distributors and HT connections on vehicles, so I guess it will do.
Any unsuppressed (no resistor) plug cap will do.
I'd offer to get you ten (It works out cheaper for ten) and post them to you, but I've no idea how reliable postage is from UK to your location. I assume you're in Russia. My girlfriend's brother lives in Moscow and I know he doesn't trust the postal service.
He gets stuff sent to us, and collects it when he comes over. He's here at the moment, but not returning to Moscow until the end of August, and I assume you don't want to wait that long.
Registered Member #9711
Joined: Sat Jan 19 2013, 03:27PM
Location:
Posts: 65
Thanks, Ash, but I did get lucky today with the local auto store. They had a spark wire repair kit that included a 2 meter wire and two sets of 90 degree boot ends. Now I'm just waiting on some silicone tubing to arrive by the weekend, and I'll slide the tubing over the wire.
Only issue now is the existing HV cup from the multiplier that I siliconed to the tube's one end: how can I break the silicone bond there and remove the cup along with the existing silicone?
Registered Member #9711
Joined: Sat Jan 19 2013, 03:27PM
Location:
Posts: 65
Vlad wrote ...
Thanks, Ash, but I did get lucky today with the local auto store. They had a spark wire repair kit that included a 2 meter wire and two sets of 90 degree boot ends. Now I'm just waiting on some silicone tubing to arrive by the weekend, and I'll slide the tubing over the wire.
Only issue now is the existing HV cup from the multiplier that I siliconed to the tube's one end: how can I break the silicone bond there and remove the cup along with the existing silicone? You can see the way I siliconed it from the images I posted before.
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best ways to minimize HV arcing/ spraying?
