Faxitron MX-20 x-ray system teardown

[mikeselectricstuff]

Might be worth asking on the UK tesla coil list if anyone has any tx oil, or knows where you can buy sensible quantities.
http://tcbouk.org.uk/

[Fraser]

Thanks Mike, will do.

I have some more detail to my post as well. The little PC is quite a fun little unit. Completely stock so I could use it as an embedded PC for other projects if the X-Ray use does not work out. I am also now aware of what a VIA C3 Nehemiah processor is and what it can do. Its an interesting CPU that has been tuned for embedded use and follows some of the RISC methodology in its design. Pretty clever of VIA to aim at a specific area of the market where they could produce what the target audience wanted without competing with the big boys AMD and Intel. It is still a very slow CPU by modern standards though. Good enough for an X-Ray machine however 

Aurora

[mikeselectricstuff]

Before putting any work in, probably worth at least checking that the tube filament is intact.
Probably little risk of it not being gas intact as it would be full of oil if not.

[Fraser]

Filiment already checked and OK   Transforner in the head could be toast but that's a chance I will have to take. No access to the inside of the generator head is possible as it is a large lead box, soldered on all sides.

I found a decent company named eden oil who will supply transformer oil. I note from the specs that it is good to 40kV before drying and >70kV after. I have read that heating the oil before pouring it into the generator removes much of the moisture and adding a Vacuum is even more effective. Hot oil is nasty stuff though so I will need to do some planning. Is it worth the effort I wonder ? Hmmm not sure. I can likely get another mail scanner for not a lot of money so will not be spending much on this one.

http://www.edenoil.co.uk/store/6/transformer-insulating-liquid/order_desc?gclid=CJXcobeUsMMCFcSWtAod2y4ARg

I am looking at around GBP50 inc VAT for recycled transformer oil or GBP84 for new.

I am so spoilt with the high resolution MX-20 that my enthusiasm for low resolution X-Ray mail scanners has waned somewhat.

A project that will have to wait me thinks.

Readers of this thread looking for an X-Ray capability may wish to think carefully before buying an X-Ray mail scanner...... the resolution needed for electronics and detailed imagery is just not present in such units as it is not a necessity for the task that they perform. The FAXITRON products are high resolution for detail work and diagnostics. The down side is the poor penetration through metals.

I just checked what the lead is worth in the Mail scanner.....£0.60 per kg (2015 scrap price) and I reckon there is at least 100kg of lead in it. £60 scrap at worst 

http://www.greengatemetals.co.uk/scrapmetal/prices/

Aurora

[Fraser]

I decided to invest approx £30 in the mail scanner unit to see if the X-Ray generator works.

After some investigation and searching on the WWW I tracked down a UK supplier of transformer oil in quantities of 5L  I have ordered it.

http://dwyforoils.com/index.php?route=product/product&product_id=210

GBP19 +VAT + Postage. Not too bad

I have also read that 100% pure mineral oil from a chemist will work up to 220kV with ease when used to insulate a  voltage multiplier ladder. But then distances between EHT p.d's may be greater on those. The pure mineral oil costs roughly £11 per litre, so the Dwyfor oil is actually a lot cheaper and I should have plenty spare for other HV projects.

My intended approach is to heat the oil to drive off any moisture and then let it cool before applying a low vacuum to the generator and then after an hour allowing the oil to be pulled in via a pipe connected to the second filler port. Should be good fun and a new area in which to gain experience. Fortunately I have the perfect vacuum pump as well. It uses an oscillating double ended piston that is driven by a field coil. It auto limits when its maximum vacuum has been reached (the piston just travels a shorter stroke until the vacuum is released again). I just knew I would find a use for that pump one day

As stated, this project isn't my highest priority at the moment but I don't think I am going to be able to keep away from it for long 

Aurora

[coppice]

I have also read that 100% pure mineral oil from a chemist will work up to 220kV with ease when used to insulate a  voltage multiplier ladder. But then distances between EHT p.d's may be greater on those. The pure mineral oil costs roughly £11 per litre, so the Dwyfor oil is actually a lot cheaper and I should have plenty spare for other HV projects.

Any oil will work up to 220kV is you have enough of it.  If the equipment has been built to be compact it has probably been built with the expectation of using a custom insulation oil. It might even require a silicone oil, which is usually used in the most compact systems (e.g my own experience with airborne radars). Insulation oils can be seriously hygroscopic, especially the silicone ones. Unless you seal the chamber well after drying the oil, your high voltage chamber can quite quickly regain a cheery glow when operating. 

My intended approach is to heat the oil to drive off any moisture and then let it cool before applying a low vacuum to the generator and then after an hour allowing the oil to be pulled in via a pipe connected to the second filler port. Should be good fun and a new area in which to gain experience. Fortunately I have the perfect vacuum pump as well. It uses an oscillating double ended piston that is driven by a field coil. It auto limits when its maximum vacuum has been reached (the piston just travels a shorter stroke until the vacuum is released again). I just knew I would find a use for that pump one day

I think you have to heat the oil a lot if you want that to drive off moisture. Low pressure is the key thing. If your high voltage chamber can stand the low pressure, you may be able to dry the oil out in place with a vacuum pump. We used to transfer the oil to a separate oil drying machine. It was basically a lower pressure chamber. It heated the oil while the vacuum was applied, but I think was just to speed things up by reducing viscosity on a cold day. I think only the vacuum was essential. That machine monitored what was coming out of the oil, so it could tell when the process had run to completion. It ran for quite a while, but it was years ago, and I can't remember just long it took.

[mikeselectricstuff]

My intended approach is to heat the oil to drive off any moisture and then let it cool before applying a low vacuum to the generator

Do you know that the generator housing is designed to withstand a vacuum?

[Fraser]

@Mike,

Well it is certainly a hefty beast and I recall that it is steel, covered in thick lead so the outer case should be fine. The X-Ray tube sits in its own separate sealed section that is still filled with oil. I can see a small air bubble in the generator output window when the unit is inverted (not inside the tube though) 

I was intending to pull a low vacuum on it, not high enough to distort the case. The inductive linear piston pump I mentioned is not capable of such dramatic pressure differentials.

Thanks for thinking of that risk though.

Aurora.

[Fraser]

@coppice,

Thanks for the information. I will not heat the oil as that was something I was not keen on. I will pull a light vacuum on the unit and capture moisture in an in line dessicant pack. I can leave the pump running for days if needs be as it is 24/7 rated. All good fun.

When all is said and done, if I fail, I have learned much and lost only £30  Plus I can still use the left over oil for voltage multipliers 

Aurora

[Fraser]

For those interested to see the internals of the Todd Research Basix30 mail scanner I attach some pictures showing the interior and damage to mine.

[Fraser]

 The Todd Research X-Ray Generator.....

[Fraser]

Saved image found on Todd Research Basix30 and captured with my camera viewing the LCD monitor so expect artifacts ! Gives an idea of the image detail, or lack there-of !

[Fraser]

For anyone needing a description of the Basix30 layout.......

Top down

X-Ray generator emitting downwards into inspection chamber
Inspection chamber for DUT
Scintillator plate
Lead glass plate screen for camera
Camera looking vertically through lead glass at image on scintillator plate
Power supply section for generator, PC & camera.
Embedded PC controlling Generator & image capture from camera

And that's all there is to it 

A camera viewing a scintillator plate that is illuminated by an X-Ray source.

Aurora

[Fraser]

Good service from the Transformer Oil supplier. 5 Litre container of EXOL insulating oil arrived this morning 

[SeanB]

I needed 2l of oil a few years ago, so got the 25l drum. Finally have been using it as a light lubrication oil, and as an air mist lubricant for pneumatic parts at work. Finally got the last 5l drum nearly empty now. Even gave 10l to the metro guys one evening doing an oil change, as they were short on their 210l drum, having used all of it during the day on other jobs. Was either that or them leaving the job till the next day to fill, doing the routine filtering and dewatering of the transformer supplying the neighbourhood. You have some that sits in the filter and the vacuum boiler. Amazing the sludge that can build up at the bottom of the tank.

[Fraser]

I was very pleased to be able to buy just 5L instead of 25L. I already have a stockpile of motor oil for my Moke etc and don't need a large tank of transformer oil at the moment. I believe that my supplier just decants 5L into their own bottle from a larger drum. It may cost a little more per litre but I am certainly happy.

This little project has caused me to do some on-line research on removing molecule level water from oil...... most interesting I must say. I now know that a vacuum is applied in order to lower the boiling point of the water so that less heat may be applied to evaporate out the water, leaving the oil unharmed or degraded. The vacuum dehydrators are specialist kit and said to be uneconomic for all but the most serious of oil users. It is also possible to remove the water by heating the oil to over 100C for a short period of time. Not without risk to me or the oil however. I will need to read the specs on the flash point etc. I have a laboratory hotplate that can go to 220C so maybe that would be of use. An air dryer is also used and air fed into the drying chamber to collect the water vapour. I have no such capability. I can either heat the oil to say 110C for a while and leave the water to escape, or I can place the oil in an air tight container, Vac it down as much as possible and heat that until water would easily boil off. I can do a test with just water in the vessel and watch it.

http://www.machinerylubrication.com/Read/503/removing-water-in-oil

I believe I would still need to vac down the Generator in order to ensure that the oil fills any air voids in the EHT transformer.

This is a job for a day when I have plenty of patience and time !

What a PITA that the oil was removed from the Generator    On a positive note the original oil would have been circa 2006 so the unit may benefit from  new 'dry' oil.

If nothing else, this Mail Scanner has introduced me to the world of dewatering transformer oil 

Aurora

[SeanB]

Get an old pressure cooker 9 a small one) and replace the vent with a pipe fitting that fits your vacuum pump, then fill with oil, place on a stove and heat to 100c then vacuum for an hour or two, then turn off the heat and leave under vacuum overnight. That should dewater it well, though you will have to be careful of it foaming up initially as it degasses. Then suck into the unit as you were going to and vacuum it as well. that should give a very dry oil. Tip during the transfer is to use a diesel fuel filter to remove solid components in the oil. New sealed filter used dry, and the new piping washed out with IPA to get the dirt out. That will clean it nicely.

[Fraser]

Thanks SeanB    Great plan, and one that I will follow.

Aurora

[Fraser]

A useful little accessory for use with X-Ray machines arrived today

Gammex produces test grids and resolution test pieces for the testing and alignment of X-Ray machines. They are normally horribly expensive, and not very common on the secondary market.

http://www.goldwei.com/products/item.asp?itemid=118&catid=3

I saw such a test piece on e*ay and snapped it up as it can be used to check focus and also ensure that the resolution is at least as good as the test piece maximum lp/mm specification.

The test piece is constructed from a 0.1mm thick lead foil, encased in plastic. The plastic provides rigidity and protects the fragile resolution grating.

My test piece only goes down to 5lp/mm but is certainly adequate for my needs. DIY 'minimum wire gauge' test pieces may be built using various diameters of wire laid side by side on a rigid frame such as that used for 35mm slides. I have yet to get around to making one.

For interest I attach pictures of the test piece but please be aware that the image resolution is limited to 640x480 !

Aurora

[EEVblog]

Just saw this interesting looking (but not cheap) Faxitron DX-50 on ebay, any good?
http://www.ebay.com.au/itm/FAXITRON-X-RAY-DIGITAL-BIOPSY-SYSTEM-DX-50-DC-2-/231462884875
No PC it seems.

[Fraser]

Sorry Dave, Walk away 

1. If it was all there (which it isn't) you would need the dedicated PC interface card to access the camera.
2. You would also need the Faxitron DR software that I am using... that could be arranged 
3. The camera is the smaller version of my DC44. The DC2 is IIRC a 2"x 2" unit.
4. The real killer...... the DC-2 camera does not appear to be present. It would normally sit under that black square visible in the underside images. The missing bottom plate shows that it has been either raided for parts or decommissioned. The X-Ray tube could also be disabled or missing 

A heavy paperwight.... and an expensive one at that !

The DX50 was designed for very small biopsy work and the small size of its inspection chamber would be VERY limiting indeed. It is also completely PC driven and will not power the X-Ray generator unless commanded to do so via the software.  It is basically missing the front panel thathe MX-20 has.

Aurora

[mikeselectricstuff]

Sorry Dave, Walk away 

1. If it was all there (which it isn't) you would need the dedicated PC interface card to access the camera.
2. You would also need the Faxitron DR software that I am using... that could be arranged 
3. The camera is the smaller version of my DC44. The DC2 is IIRC a 2"x 2" unit.
4. The real killer...... the DC-2 camera does not appear to be present. It would normally sit under that black square visible in the underside images. The missing bottom plate shows that it has been either raided for parts or decommissioned. The X-Ray tube could also be disabled or missing 

A heavy paperwight.... and an expensive one at that !

The DX50 was designed for very small biopsy work and the small size of its inspection chamber would be VERY limiting indeed. It is also completely PC driven and will not power the X-Ray generator unless commanded to do so via the software.  It is basically missing the front panel thathe MX-20 has.

Aurora

Maybe worth PMing this guy :
https://www.eevblog.com/forum/projects/help-faxitron-dx-50-specimen-x-ray-system/msg421306/#msg421306

I don't see a camera inside that unit - looks like it's been removed

[Fraser]

X-Ray DOSIMETER Choice


As has been stated already in this thread, correct procedures and equipment are important when operating X-Ray equipment. With this in mind I did a review of my dosimeters to ensure that they were appropriate for use with the Faxitron and Mail scanner.

The sad truth is that most Geiger Muller based dosimeters are pretty much useless when used with X-Ray energies of less than 30KeV and even that level is too low for many meters. It should be understood that a meter with a detection capability of >50keV will not provide any meaningful reading when exposed to a 30keV X-Ray field. Always look for the keV capability rather than just the uSv specification !

My dosimeters are right on the edge of detection at 30keV, so I decided it was time for something better that matches my Faxitron's output.

Some research pointed me in the direction of the Thermo EPD MK2 range of dosimeters. The standard version is designed to detect and measure Gamma, Beta and X-Ray radiation at energies as low as 15 keV, which is perfect for use with the Faxitron.  Various tests by official bodies have proven the EPD Mk2 unit to be very effective at low keV levels, unlike many other brands of unit. It uses three special pin diodes as the detectors rather than an ionisation chamber or Geiger Muller tube.

There are two down sides to the Thermo EPD however......

1. Price. They cost around $1000 each new.
2. Software configuration - the software costs $1000

Those prices are not hobbyist friendly but it is a health and safety device and such tend to be expensive.

I managed to find a new unit on ebay and negotiated a price of £200 which is still quite a sum but what value your health eh ?

Now to the software issue........ The Thermo EPD is quite a sophisticated device that can work stand-alone or as part of a monitored collection of units as in a  team situation. The software contains a database and graphing software showing dose readings over time. Pretty useful but not cheap at $1000. The other issue is that the software can configure the dosimeter and disable some menu options to prevent tampering. That is all very well until you buy a used unit that has had its menus disabled ! As standard, the EPD can be configured using its built in menus, if these have been disabled to prevent tampering, the unit is basically locked to a specific configuration.

The EPD Mk2 communicates with a PC vis an IRDA interface so hopefully that part of the software control is not a problem. My unit should come in standard unlocked condition but just in case it doesn't, I have managed to obtain the EPD software.

Once the unit arrives I will advise on the Thermo EPD performance and whether I can access it via the software version that I have. Watch this space.

If anyone is thinking of buying a decent low keV capable Dosimeter, look out for the Thermo EPD Mk2 and NOT the Mk1 which is an old Siemens version that is a nightmare to control.

Aurora

[Fraser]

Radiation test source

Further to my comments on a Dosimeter, it is also a good idea to have a radiation test source with which to check your dosimeter.

Some Dosimeters come with a test source but most do not. A used one is very unlikely to come with such. So where do you get one from ?

I have come across two easily obtainable radiation test sources

1) Fiesta Orange or Red crockery from Circa 1930 Uranium glaze  - Alpha emitter
2) The Americium 241 source installed in an ionisation smoke detector- Alpha emitter

The Fiesta crockery may be found on ebay for a few pounds per square inch, or maybe find some in a thrift / charity shops ? It is more common in the USA than UK.

The ionisation chamber of any ionisation type smoke detector contains a small gold coloured pellet of Americium 241 at the bottom of the chamber. You can extract the chamber and use it without the top shield as a test source. A word of warning, the bulk purchase of ionisation smoke detectors can attract the attention of your local authorities ! They are also a banned product in some countries due to their radioactive content.

The above freely available and safe radiation sources are legal to own and use but you must not ingest the source in any way as it is a harmful Alpha emitter, that once inside your body is very bad news.

Both are Alpha emitters but they also produce Gamma or Beta radiation as a bi-product. They work well when used with Geiger counters and other types of radiation dosimeters that can detect Alpha, Beta or Gamma radiation.

I understand that unused 'new old stock' gas mantles are also used as radiation test sources as they contain radioactive Thorium. I have not tested such however. The Thorium impregnated types are apparently now illegal in the USA.

Aurora

[TopLoser]

I can never miss a chance!

Found one of these in a corner under my desk...

http://en-us.fluke.com/products/hvac-iaq-tools/fluke-481.html#techspecs

Detects radiation 7KeV and above.