Faulty medical X-Ray imager - Page 1
Forum section: electronics / repair

author: TerraHertz
author_rank: Super Contributor
timestamp: December 31, 2020, 07:51:36 am
content: So here's a Hamamatsu C10900D-05 X-Ray imager. It's faulty, and is out of a very expensive machine that the owners would like to get working again. But there is no service support available from the supplier, and apparently no schematics or service info available from Hamamatsu. (I'm told, have yet to verify for myself.)There is a specs sheet (attached.)So as it stands it's a dead loss. I offered to have a look at it. Can't get any worse.The unit consists of two layers, screwed together. One is the drive electronics, on a conventional PCB. From that a single connector joins to the sensor structure. That has a thick PCB, and a protective carbon-fiber cover glued to it. There's a solid metal plate between the two boards, presumably to shield the electronics from the X-Rays.From first impression it seems I won't get to see the actual sensor plane without destructively opening it.I haven't disassembled yet, beyond taking the metal protective cover off the drive PCB.Right next to the interconnect, there's a row of 8 AD9220 AtoD converters.The unit fails self test mode in the machine, giving the image cal_fail.jpgThis *should* be a solid dark gray square field at top, and a light gray field at bottom. I gather they are results of reading the square sensor array at different biases (no X-Rays.)The white horizontal stripe in the top square is the fault. Shouldn't be there.I notice that it seems to be one eighth of the field. Corresponding to one of the 8 AtoDs maybe?The plan of attack is to have a better look at whatever is visible without opening the sensor plane. Then cart some test gear to the location with the machine (it's not easily movable), run test mode and see if there's any obviously wrong signals around any of the AtoDs.Has anyone any suggestions?What are the actual sensor devices? Charge accumulating diodes maybe? I suppose there will be some kind of CCD charge shift registers (8 of them), to clock pixel data out serially. And if something in the sensor charge shift registers is dead, then it won't be repairable.If the fault is on the drive PCB, and can be identified (without schematics) then it probably can be fixed.

author: aqibi2000
author_rank: Regular Contributor
timestamp: December 31, 2020, 11:26:03 am
content: You could move all 8 A/D one position if just stabbing in the dark

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: December 31, 2020, 11:40:39 am
content: Definitely check all the voltages on the ADCs to see if there are any differences.My money would be on a dodgy tantalum cap

author: Manul
author_rank: Super Contributor
timestamp: December 31, 2020, 02:01:44 pm
content: While these ADCs could be a culprit, I would also look how the sensitive array (photodiode array?) is driven. That could well be a driver problem.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: December 31, 2020, 05:22:30 pm
content: Quote from: Manul on December 31, 2020, 02:01:44 pmYes, but as there are 8 ADCs, it seems likely that it is outputting 8 parallel output streams, and the drive for each stream is likely to be common.If you can get the panel into a continuous-reading state, it shouldn't be hard to compare the signals going into each ADCAnother suspect would be whatever it uses to connect the CCD array to the main PCB.

author: madao
author_rank: Frequent Contributor
timestamp: January 01, 2021, 06:50:30 am
content: Yes, flat panel works with CCD . It is just a big CCD sensor with scintillator onboard.I have repaired successful few xray flat panel from Varian. Failure of CCD is not rare -> not fixable :-(

author: TerraHertz
author_rank: Super Contributor
timestamp: January 01, 2021, 11:16:02 am
content: Some more pics, after separating the driver and sensor panels.8206 The metal plate between the two modules. Gratuitous over-CAD, making that mill show off. Why didn't they revert to straight cuts?8208 Back side of the driver board. Sigh... more stuff that might be faulty.8210 The accessible side of the sensor module.sensor_03.jpg Same, but in photoshop for tracing.Interestingly, all the trace vias are blind, and the the only PCB holes are a grid of small non-pad holes that don't appear to be electrical.There's a repeating pattern, times 8. The pattern on the left in the last pic is arranged a little differently due to a layout problem. Looking at the repeated patterns of vias in a row, you'd think all the elements would be bused along some buried traces, and would come out on J1 pins. But no! Some pins are NOT bussed, and don't go to J1 individually either. They just vanish. Maybe they are pins of the sensor CCD(s) brought out to caps?Not many pins of J1 are involved with the visible components. Either there are a lot of unused/power pins, or a lot of signals going to the CCD sensors via hidden traces. Far from finished with this.Bah. I need to go through my multimeters to find one with an audible continuity test, that's low freq enough for me to actually hear. (My hearing HF is gone. Age.)

author: CaptDon
author_rank: Super Contributor
timestamp: January 01, 2021, 02:49:40 pm
content: That milling appears to be used as collumation to keepthe electron path straight to keep the X-rays 'focused'so to speak. That is a weird milling pattern. Very sadthat no replacement parts are readily available andwould cost an insane price anyway. Got any leads tolocal BioMed techs from a hospital/imaging center?Chances are they have only done module swappinganyway. I worked as a BioMed Tech for 5 years. Thehospital decided there would be no more componentlevel repairs, only module swapping. My lab now hasmost of the discrete components that were destinedfor the hospital dumpster. I gave away hundreds ofpounds of stuff to Vo-Tech schools and Trade Schools.Rather see kids play with the stuff than just go directlyto the land fill.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: January 01, 2021, 04:19:24 pm
content: If you can't fix it, it would be worth putting the sensor part number as a saved search on Ebay - you never know when stuff like this might turn up eventually.

author: TerraHertz
author_rank: Super Contributor
timestamp: January 01, 2021, 08:32:09 pm
content: Quote from: CaptDon on January 01, 2021, 02:49:40 pmNo, the sensor is directly in the X-Ray path, and the metal plate is _behind_ the sensor, in front ofthe drive electronics board. The weird milling pattern is 'just because they could.' It's actually quitesmooth, the light is reflecting off the very tiny milling imperfections. It's not any kind of Fresnel lensfor X-Rays.QuoteVery typical of corporate thinking. 'Repairable' = less profit.QuoteOh I wish. I'm sure the local hospitals dumpster all their surplus equipment,and would recoil in accounting horror at the idea of making it available toanyone.QuoteYou were a rare exception.I currently know of an unbelievable example of criminal wastage about to happen.Large room full of a huge component stock from a major electronics repair facility.It's probably all going to be bulldozed. But I will try to see if it can be saved. Don'thave much hope of success.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: January 01, 2021, 08:47:15 pm
content: Have you asked Hamamatsu if a replacement is available, and the cost ?

author: madao
author_rank: Frequent Contributor
timestamp: January 02, 2021, 01:04:43 pm
content: if you ask cost, pleas sit down, before you got answers.I can tell: over 40k€ priece

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: January 02, 2021, 04:05:37 pm
content: Quote from: madao on January 02, 2021, 01:04:43 pmThat doesn't surprise me, but if it's in a $400k machine....And at that price, selling to manufacturers of expensive equipmet, they should offer a repair service

author: MadTux
author_rank: Frequent Contributor
timestamp: January 02, 2021, 05:36:11 pm
content: Perhaps partially erased/corrupted FPGA config EEPROM/Flash?1000s of xray exposures probably isn't healthy for them as well.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: January 02, 2021, 05:49:13 pm
content: Quote from: MadTux on January 02, 2021, 05:36:11 pmPretty sure these have CRCs, so it will do nothing if the FPGA doesn't get configured

author: MadTux
author_rank: Frequent Contributor
timestamp: January 02, 2021, 06:29:53 pm
content: Quote from: mikeselectricstuff on January 02, 2021, 05:49:13 pmMakes sense