EBME Forums Forums Maintenance Technical Assistance mammpo lorad M III

Hi,

My mammography system (Lorad M III) is showing the following message during X ray eposure:

filament power supply

any help woill be appreciated :

Apart from the pretty strong clue that you've already furnished there, Djiela what else is going on?

That is, what are the results like? Does it actually expose? Are the radiographs a bit on the light (or transparent) side ... indicating low filament current?

If the message actually mentions the filament power supply, that sounds like "good news", as (hopefully) the fault will be in the filament supply, rather than in the tube itself. But, having said that, filaments usually just go open-circuit, resulting in no exposure at all.

So, low filament current is suspected, but more clues are required!

Dear GEOFF,

actually, it does not expose.

You said more clues are required and that is what i will like to know Geoff.

OK ... can you get at (and measure - for continuity) the tube filament?

Perhaps it's "gone" (as in, open circuit).

If so, that's bad news (of course), as it will mean a new tube is required.

Dear GEOFF,
well i have check the filament and the continuity is going through. the filament (small, large and common filament) is control by tube control board.
i have done several test:
with the filaments disconnected, at the start up, it shows filament supply error
the following voltages where taken at the standby and during explosure:
standby/ explosure
com - large: 2.66 V 7.56 Volts
com - small: 0 V 0.16 V
groung - com: 4.62 V 6.02 V
groung - small: 4.71 V 6.20 V
groung - large: 7.29 V 13.24 V

so i do not know if these voltages are normal

Best Regarg

Well, I know that I mentioned earlier today that "rust never sleeps", but perhaps I should admit that it's 13 years now since I last had a go at an x-ray set in anger, as it were! So, I could well be a bit rusty here, as you can probably tell.

However, and having said that, I would say off the top of my head that the results you mention would give cause for encouragement, if I were there doing the job myself (and without any information to the contrary).

There is "something there" (which is always nice), and the voltages boost during exposure, which is what you might have hoped for. An indication saying "Filament supply error" when the filaments are disconnected sounds good, too, I would have thought.

OK, so the filaments themselves are OK. And it looks like there's something coming out of the filament supply. Voltages, at least (but I wonder whether a loss of current is being hinted at by the error message ... there's no sign of any insulation breakdown anywhere, I suppose). All good news, then, on the face of it.

So, I think you need to go back and try to establish where the "Filament power supply" error (?) message you mentioned earlier is likely to be generated from. That is, what triggers it? An attempt at too much current being drawn (and indicative of a "short" somewhere)?

Have you got the filament power supply open? Have you had a good look at it (fuses, obvious signs of distress, unwelcome smells, and that sort of thing)? What's it like? The (old-fashioned) transformer based type, or some new fangled arrangement? Is the transformer looking good?

And ... are the (mA) settings in the realms of the real world? Can they be varied? Or have they become "stuck up" in some way? Or, perhaps mA is fixed on this mammo unit (and just switched at broad and fine focus ... why both on a mammo, I wonder)?

hi friend , you need filament calibration 1.shutdown 2.micro bd. switch S1= cal 3. select = 0 mode filament calibration ,you shoot every kV station . if overshoot you can set kV \/ down , if undershoot you can set kV ^ up

Dear friend,

I have tried the filament calibration and i have had the following results:

First of all, i could not locate the tube sensor resistor.

secondly, with the small spot, 22 kV, while increasing the filament current (with the KV up and down) i had these messages:
from 16 to 176: KV sense error
from 177 to 255 and 0 to 15: filament supply error

thirdly, with the large spot, 22 kV, while increasing the filament current (with the KV up and down) i had these messages:
from 33 to 221: KV sense error
from 222 to 255 and 0 to 32: filament supply error

And after this calibration test, during an explosure the actual message is control error.

So that's is the beheviour of the equipment presently.

How can solve out this problem.

Best Regards

An improvement on what you had before, then?

Off the top of head, it sounds to me like the thing is basically working OK. It "just" needs to be calibrated!

But ... what are you comparing it (calibrating it) to? Surely you need some sort of tube rating (characteristics) chart to guide you?

How many check-points does the thing need to have correctly adjusted until it accepts a "cal"?

I guess all these questions are unknowns, unless you have a manual.

Can you (or anyone else) come up with calibration settings from "first principles", I wonder?

Can you start by adjusting to the point of no error messages in each selection? And from there on in ... well you really need x-ray output test equipment (or even the good old step wedge, followed by [many] test radiographs). Bearing in mind, of course, that we're talking about (relatively low output) mammo here.

Otherwise, it sounds like the only way forward is a long round of trial and error!

Dear all,

I came to a point that the problem is probably the microprocessor board. With all the test i have done i realised that the fault is resulting from that board.

I am about to buy the board(Lorad MIII mammography equipment).

I hereby thanking you for your assistance.

Best regards.