Wednesday, 25 March 2015

Packard 1000 TR Liquid Scintillation Analyser - Part 1

So the teardown progresses!

Now the analyzer is in the shed i can take a look at this in more detail.

Overall Construction
The base of the unit is made from pressed steel which is thick and sturdy. The top cover is constructed from fiberglass with cutouts for the sample loading mechanism, keypad and LCD display.

The unit consists of many components, these i will remove and produce separate videos on through my YouTube channel.

PSU Board & Transformers
The main unit appears to operate from 110/120v AC, in the unit i have there is an additional transformer which i believe drops the 220/240v AC. A secondary transformer and power supply board supply the low voltages to the rest of the unit.

Motor Control Board
Controls power to the two motors used for loading and unloading the samples.

Photomultiplier Power Supply
Creates the high voltage supply for the two photomultipliers.

Mystery High Voltage Power Supply
Not sure what this is exactly for but its output is into the sample loading mechanism, looks like an ionizer of some sorts, maybe to eliminate static charge or dust on the sample vial or something i have not thought of yet. I will have to do more thinking and research into this.

Sample Loading Mechanism
A mechanical device operated by a motor to load and eject samples and insert the radioactive source into the sample chamber.

Sample Chamber & Photomultipliers
Metal constructed unit that allows the sample to enter a dark chamber. This entire part was surrounded with 80Kg of lead shielding to reduce the background radiation count rate.

CPU, Logic & Analog Boards
Total of four PCBs located on a metal structure to run the entire instrument. These also connect to two 25pin RS232 ports located on the side.

Teardown Video

After i had filmed this and in the process of editing the video i realised i may have exposed the photomultipliers to ambient light in the process. Given the light cap that covers the sample chamber had been slightly bent, the lead shielding was removed which would have provided some darkness to what should already be opaque covering and i was using it without the top over.

Thankfully after some testing at night in darkness it is registering some count but it does respond massively to a torch being pointed at the loading mechanism so there is a certain light leak somewhere. Hopefully there is no permanent damage.