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Subject: Re: X-ray image-intensifier tube.

Date: 04/23/01 at 9:29 AM
Posted by: Joe Rongen
E-mail: joe@alpha.to
Message Posted:

In Reply to: Re: X-ray image-intensifier tube. posted by Bas Janssen on 04/23/01 at 5:52 AM:

I get no image anymore on the phosforscreen just some radom spots now and then.

>Would you know how I can test the electronics to know it is broken?
>It uses 24 volts and up to 0.7 A, I thought it should use up 0.35 A max.

From what I have been given to understand, not all these units employed the same electronics. I'll describe the one sitting here.

The electronics are connected like this (I am not an expert when it comes to these particular tubes); The dc input is filtered and feeds an oscillator that in turn uses two transistors
to drive a small HV transformer. From there the signal travels two ways, one enters into a solid device that probably is an HV tripler. (or better) The other signal goes into a small network of parts, on a separate board, (Picker, part D-58574) that supplies the tube with two(?) more special drive voltages
I would suggest troubleshoot the unit as follows; measure the DC past the input filter and zener diode, it should be almost the same as the
input voltage: 24 Volts. Check both drive transistors and diodes for intermittent open, or disconnect the wire going to the HV tripler input
and use a scope to watch for a continuous output. Warning, the HV at this point maybe near 5000 volts AC. The HV tripler, a sealed unit, can
give you similar bad results. All one can do is replace it and hope for the best. The two controls on the side are mounted on a board with a resistor divider network. Here again to troubleshoot, HV to 2000 Volts, use proper equipment and look for variations during readouts.
That's about all I can think of at this moment.

>Because of a project I'm in a rush and if you as a user could tell me a method to check >the electronics or the vacuum a bit more pragmatic then the manual it would be of great >help.

If the tube had a loss of vacuum than the tube would tend to progressively get worse with time. There is no way of checking a vacuum, but HV arcing inside a tube would be a sure warning.

Hope this helps,

best regards
Joe Rongen
Ontario, Canada

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