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Opening the Case

A project log for Xray Head Teardown

Reverse engineering a dental xray head

drhatchdrhatch 12/22/2014 at 22:340 Comments

The first thing to notice about the head is:

1) The 6-pin molex connector plus earthing wire.

2) The long tube, which is where the xray beam comes out of the head.

3) The aluminum plate at the base of that tube. It filters the xray spectrum. More on that in future posts.

Opening the case was the first step. I know that these cases are full of insulating oil, so I had to be prepared for draining the oil prior to further disassembly.

I opened the case through the electrical port, drained a bit of oil using a "turkey baster" type of syringe, drained some oil, then tipped the case to finish extracting the oil.

NOTE: I do not know what kind of oil it is, nor if there are any hazardous additives, so I treated it very carefully, cleaned carefully, and stored the oil in sealed containers. There was a total of 1 liter of oil.

After draining the oil, the next step is to access to the internal components from the "back end" of the chassis.

Now were are getting somewhere!

There is an earthing wire soldered, so I un-soldered that. NOTE: the wire is soldered to a soft lead sheet piece that (along with the steel chassis) shields the outside environment from xrays.

After lifting the shield assembly out, we see the xray tube.

The half-cup of light gray on the left of the shield (that I am lifting off in the photo below) is 1.0 mm thick. The half-cup of light gray on the right of that part is 0.7 mm thick.

It is interesting that the shield closest to the tube is thicker than the piece that is only slightly further away (1.0 mm versus 0.7 mm).

After removing three screws holding the tube/transformer assembly into the case, it lifts out.

Now that I have full access to the internal components, I can begin the investigation and analysis.

One early discovery/surprise is that the xray tube is located at the rear of the unit and fires toward the transformer. I more-or-less expected that the tube would be at the front of the unit (toward the output cylinder) with the HV transformer behind the tube, not the other way around.

This is possible because the transformer has a hollow core tube, and that tube is lined with (probably) ferrite.

This means that the transformer, besides creating the high voltage, is also acting as a beam collimator, narrowing the output beam by blocking the outside portion of the xray cone.

In the next posts, I will explore the components and conduct some experiments to characterize them.

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