Inframetrics / FLIR PM280 cooled thermal camera teardown for repair

[Fraser]

I am fortunate enough to now own two Inframetrics / FLIR PM280 Stirling Cooled thermal cameras.

One was bought some time ago and proved to be a bit of a bum deal as the camera did not work. Yesterday I was kindly gifted another PM280 that was described to me as very noisy. My sincerest thanks to my fellow forum member for gifting such a nice camera to me. He knows who he is 

I just thought 'typical Stirling Cooler noise' ....... oh how wrong I was 

I fired up the camera and was greeted with a sound akin to  a mass of ball bearings in a tin that is being shaken    One very sick Stirling cooler  The amazing thing is that the cooler actually reaches -196C and the camera works well. The cats were not amused with the noise and scattered and I must say I had to muffle the noise with a towel as it is just so loud !

I was quite frankly amazed that the noisy camera was working. My original PM280 is younger and sounds very sweet when running. I had originally thought that its cooler had run out of gas but I am no longer sure. Maybe it has or maybe there is another fault that means the camera never sees the correct -196C detector temperature that it is looking fro, so all functions work except image production ? Wishful thinking on my part I know. It would be so great if I could make one good camera out of two poorly ones though 

I dismantled the noisy camera today as I will be giving it a good clean and service anyway. As I know some members of the forum have an interest in what lives inside such a camera, I have taken some photographs for you. The PM280 is a bit of a pig to work on though. Nothing like as simple to disassemble as the FLIR PM 5xx and 6xx cameras. The PCB's form a box around the detector and cooler and that makes access for fault finding a bit of a nightmare. Its an old school pcb configuration often seen in older Vidicon CCTV cameras and I dislike it. Getting at the microprocessor board is a total nightmare. You must remove the cooler and detector assembly in order to gain access, and then the pcb can be removed. NIL points for technician friendliness    How the heck are you supposed to fault find to component level when the whole camera has to be stripped to the chassis in order to get at the pcb that has the 'brains' on board. This type of camera layout is designed to be worked on using long pcb interconnect extension cables and PCB jigs to hold everything in place. It is also a sad fact that most repairs would in fact be just PCB replacement with no 'on-camera' diagnostics to component level.

I will try the working cameras PCB's with the non-cooling cameras detector and cooler to see whether the cooler is unserviceable or not. If its actually working, I can decide which boards need to go with which detector and, if required, trace the fault to source if a board is detector  specific. I can always transfer the calibration and dead pixel map FLASH chips onto the the known working detector board if that is needed. Lots of options but little time to play at the moment. This will be an ongoing project over the next few days or even weeks.

Here are the pictures.... there will be quite a few !

Fraser

[Fraser]

More pics

[Fraser]

More pics

[Fraser]

More pics

[Fraser]

PCB Pics

[Fraser]

Close-ups of ICs

[Fraser]

And here are some pictures of a camera that I was not interested in rebuilding ! Sold on ebay for over $300  Crazy, totally crazy.

What a mess....typical destruction before disposal stuff....but they should have smashed the detector array as well.

[Fraser]

See this thread that I wrote about my first PM280 that turned out to be a lemon.....

https://www.eevblog.com/forum/thermal-imaging/thermal-camera-purchasing-the-perils-of-buying-a-cooled-camera/msg702367/#msg702367

The other (non working) camera is now stripped down and running with the Power Supply PCB, Low Power interface PCB and PCMCIA interface PCB from the working camera. She is running the cool down phase at the moment but I am really just looking to remove those three PCB's from the 'possibly faulty' list. I need to change out the microprocessor PCB really but that is too much work fro tonight.... its been a long day.

Goodnight all 

Fraser

[Fraser]

Well you could knock me down with a feather..... the previously faulty PM280 lives 

I was happily tidying up for bed when I noticed the noise of the cameras cooler had dropped significantly. A quick check provided the reason. The cooler had reached its -196C temperature and the camera was presenting a very nice thermal image to me ! The cooler is purring away at tick-over keeping the detector array cool with ease.

So one of the PCB's that I changed out has a fault on it. Pictures of the three suspects are attached and a quick picture of the PM280 image output. I will digitally capture some later for upload.

I suspect the faulty PCB is the low power interface as that connects the detector to the microprocessor PCB. It is the one in the foreground of the picture.

I can go to bed a very happy chap now :-)

Fraser

[Fraser]

Well after a quick test today the PCB responsible for the fault is the usual suspect, namely the power supply board. No idea as yet why this is affecting the reporting of the cooler getting down to temperature but it could be that power and sensor communications connect to the cooler via this PCB and something has gone wrong on the communications front.

Fraser

[bookaboo]

Great job, unexpected wins are always the best.

[Fraser]

Yes, especially as I had seriously considered selling the non working PM280 for whatever I could get on eBay, only a few weeks ago. I mistakenly thought it was beyond repair. Had a very kind Gentleman not gifted me the noisy unit, I would still be thinking it was the cooler that was at fault. My sincerest thanks to him.

I repaired his FLIR thermal camera and he indirectly helped me repair my PM280 ....... That is good Karma for you

Fraser

[Fraser]

To complete the teardown of the PM280 I am including some pictures of the lens and the EVF.

[Fraser]

EVF

[Fraser]

As any good Service Tech knows, you have to be able to correctly rebuild a unit after a complete strip down. Failure to master methodical disassembly and re-assembly is a recipe for disaster or bits & bobs left over at the end of the job 

I have just rebuilt both PM280 cameras and all went as planned. No parts left over !

Rebuild of Noisy Camera pics follow.

The suspect power supply board was tested in the known operational, but noisy, camera and sure enough it failed to come out of cool down mode and display a picture.

Fraser

[Bill W]

Great job Fraser 

Is the lens a diffractive ZnSe front element with Ge rear ?

regards
Bill

[Fraser]

Hi Bill,

The lens has ZnS or ZnSe front element only. It has concentric rings visible on it but the lens is smooth on both sides with no evidence of stepping as I was expecting

The second lens element is Germanium but it is in the camera optical block rather than the removable lens. This is the same idea as on the AGEMA 880 that I have. Presumably it reduces the cost of the various lenses that may be fitted as they contain fewer elements within them. As you know , where Germanium is involved the BoM costing is severely impacted by using more of it in a design.

I had not seen ZnS or ZnSe front lenses before seeing the Inframetrics PM series lense. I presumed it was a cost reduction measure ? It is softer than Germanium and may be damaged more easily. My noisy camera came with a nice lens protector, IMHO, an important accessory when using a ZnS or ZnSe lens to reduce the chances of scratches.

Fraser

[Fraser]

More pictures of the lens rings....

You can look through these lenses at visible light wavelengths which is nice 

Fraser

[Bill W]

Hi Fraser,

The rings are diffractive features, which are not the same as fresnels as you get on traffic lights simply to save weight.

The big benefit of ZnSe is lower dispersion compared to Ge, so focussing all the 'colours' at the same point, and it is also less thermally unstable dn/dT.  I have seen ZnSe on rear elements of 8-14um lenses but its' main use was in 3-5 or wide band 3-14 lenses.  As you say it is softer with less scope for hard coatings so it is often kept inside.

Bill

[Fraser]

Thanks for the information Bill. I know only the basics of optics, anything out of the ordinary has me heading to Google for an explanation !

Fraser

[Stray Electron]

Fraser,

   I just found a PM 280 that is for sale.  The complete kit with case, software, manuals, AC and DC chargers, some other misc cables and one or two batteries and two lens; one 16d FOV and the other is 32d FOV.  It appears to be in great condition but hasn't been tested so no idea if it's functional.  Can you give an idea of what it's worth and anything that I need to be aware of?  I have worked with larger .MIL FLIRs and Sterling cycle pumps so I'm well aware of their problems but I know very little about these small hand held commercial t. cameras.

  PS don't really need it but I can't resist new gadgets!

[Fraser]

Stray Electron,

I know you say you are familiar with Stirling coolers but be very careful when looking to buy a PM280/290/380 when the seller says untested. That usually means they have plugged it in and no thermal image is displayed. The unit is easy to fire up, all parts are in the kit and tested cameras always sell for more than untested. So why would they not switch it on ? It is a good way to avoid any blowback Same as 'sold as seen, untested'

An Inframetrics PM series is a cooled SW camera that provides excellent low noise images. A working example produces lovely pictures but be aware it is a 256 x 256 pixel sensor array. It is not as high resolution as common microbolometer cameras but the low noise compensates for this. The operating ergonomics of the camera are not to my taste and I prefer the AGEMA PM550 cooled SW camera. For me the camera looks and feels a bit of a hotch-potch designed by a committee. This does not mean that it does not produce nice pictures though.

If you buy an Inframetrics PM series camera and it proves to be faulty, it is no longer supported. The Stirling Cooler rebuild costs more than the camera is worth. It becomes an expensive paper weight.

You need to consider the fact that the Inframetrics PM series is an elderly camera so the Stirling Cooler is a very real potential failure in the future, if it has not already failed.The vacuum in the sensor Dewar may also have decreased over the years.

Value ? That is a difficult question because I believe many very high quality thermal cameras are sold too cheap because of public lack of appreciation of the technology within and performance achievable. I took advantage of that situation though and paid well less than £1000 for most of my FLIR PM series cameras. One perfect condition PM575 camera cost me just £125 ! Crazy low price. Old does not mean no good with thermal cameras but you do need to understand the risks involved.

I regularly see Inframetrics PM 2xx and 3xx thermal cameras on ebay with Buy it Now prices of $2000 to $4000. Most, if not all, state untested for whatever reason they decide to use.... like no mains cable or no knowledge etc. This is IMHO crazy high money for a camera that may not work, or if it does, is almost at the end of its life and can fail at any time due to Stirling Cooler EOL.

I bought the PM280 for IIRC £400 and got seriously burnt. After that I decided that I would not pay any serious money for a stirling Cooled camera. The risk of loss is too great. I do have a gorgeous FLIR SC3000 Stirling Cooled Quantum Well scientific camera but I bought that well before the PM280 that turned out to be a Lemon. I have another PM280 that was given to me as it sounds like a cement mixer with a brick tumbling around in it. I wrapped it in a towel to silence it and did achieve an image. There were masses of dead pixels due to vibration damage. The Stirling Cooler main bearing has failed and acts like a little hammer inside the cooler !

If I were offered a working PM280 or 290 I would not pay more than £500 for it. I would need to actually see it working as well. By this time expect the camera to be displaying the 'maintenance needed' advisory message as well. It is a warning and not an indication of a fault. Inframetrics expected these cameras to require quite regular maintenance based on hours run and age.

Hope this helps

Fraser

[Stray Electron]

  Thanks Fraser. I hope to get another look at it and a chance to test it in a couple of days so I'll let you know what I find out.

[Stray Electron]

   Well, I went and tested the camera today. The cooler seems to be as dead as a dodo. (The owner hadn't tested it BTW, he didn't have a clue of how it worked or exactly what it was for.) I let it run for about 40 minutes the first time then tried it again later and let it run for about an hour and both times it kept reporting the detector temperature as 23d C and the ambient air temp as the same. I can hear the cooler running and it never slows down. The manual says that it should run at high speed when first turned on but once it gets to the proper temperature (in about seven minutes) it should slow down but this one never does.  How are these charged with helium?  Through a pinch off tube?  Do you know anyone that can recharge them or about what they charge or what they used to charge?  Since it's not working, the owner let me take it home to tinker with but I don't think there's much I can do with it.  Do you know how much pressure these are supposed to have?  If it uses a pinch off tube, I could attempt to recharge it. I have a 60 cu ft tank of helium. About 2,000 PSI IIRC.  I also have a small 10,000 PSI tank (thank you, NASA!) but I don't know if I could get anyone to fill it.

   PS I don't know how old this one is but it was last certified in 2005.  There's also a tag on it says to call FLIR, Inc for service so they did service these, at least at one time.

[Fraser]

What you describe is typical cooler failure due to loss of Helium charge pressure. Any camera that will not cool to operating temperature within 15 minutes is in need of a cooler service. I have the quotation for such a service on the PM280 that was provided many years ago when Inftametrics still existed. The quote was for £7900 + shipping to and from the USA. No repair facility exists for the cooler in the UK.

In 1997 a Stirling Cooler rebuild for the AGEMA 550 Stirling cooled camera was £5000 + shipping to and from Sweden.

A Stirling cooler has a finite mechanical and Helium Charge life. The OEM always quoted for the rebuilding of the cooler as well as the re-charging with helium and calibration. No 're-charge only' options were offered as the OEM did not trust the coolers Helium Gas seal integrity.

As to the specifics of the Helium Charge used. It is Ultra High Purity (UHP) Dry Helium at a pressure of around 200 to 250 PSI. No water is permitted within the cooler as that causes immediate ice locking of the pistons. Clearances of the precision pistons are truly minute and no contamination of their cylinder bores is permissible. Balloon Helium is relatively impure and these days often contains 20% air mix to reduce Helium consumption and also counter the use of Helium for suicide. It was a favoured method of leaving this mortal world.

Helium is the Houdini of gases. It will leak past seals and even through the aluminium shell of the cooler at the molecular level. To limit leakage, the OEM coats the internal surfaces of the cooler shell with a material less porous to Helium molecules. Specialist material gas seals are used where such are required to mate two surfaces. These seals are very high performance but not perfect.

The Helium fill port on the types of Stirling Cooler used in Inframetrics and FLIR cameras are an  internaly threaded hole with a precision gas seal seat at the bottom. The gas seal itself is of specialist very malleable metal that flows under pressure to create a near perfect gas seal. A threaded screw plug is inserted into the fill port and compresses against the gas sealing ring. When you think about the mechanics of the situation you realise that the Helium fill head has to be gas tight into the fill port whilst having the ability to insert and tighten the threaded plug when correct pressure is achieved. All atmospheric air must be pumped out of the coolers casing before the Helium fill may begin. The Helium fill also passes through a filter and cryogenic cooled dryer to ensure no water contamination occurs.

Refilling a precision Stirling Cooler is not a simple task as I have discovered. This is why I would not buy a cooled camera unless it was a true bargain or included accessories that I need.

The fact that your test indicated that the Cold Finger temperature of the Stirling Cooler remained at ambient suggests that the Cooler is open to air somewhere or that one of the piston connecting rods has failed. Even with sealed air inside the cooler, it will cool a few degrees below ambient. That is just the physics of the Stirling Cooler at work.

The Inframetrics PM series is a decent camera when working but sadly the camera you have tested is now little more than a nice collectors piece. It is not a viable repair proposition as a more modern camera may be purchased for less than the service cost, if such is still available.

For more information on the Stirling Cooler used in these cameras, Google RICOR. You will see that some have a longer life prediction than others. Space Rated models have a much longer life but are predictably more expensive. Stirling Cooler rebuilds in ground applications was alwYs considered part of the cost of ownership of an equipment. Hence why the microbolometer was embraced by industry with such joy. It did not have the financial overhead of the Stirling cooled cameras.

Also be aware that the cooled detector array in these cameras is part of a vacuum Dewar that is in turn part of the coolers shell. You cannot just replace the cooler with one from another camera unless you also transfer the board that contains the dead pixel map etc. Cooler and detector are a single unit and are not separatable.

Another known fault with cooled cameras is Cold Finger separation from the detector array. This is often due to mechanical shock. The symptom is often a Circukar image effect. There is a residual thermal image at the centre of the display where the Cold Finger proximity is enough to get the detector down to operating temperature, but outside the central circle there is no image at all.
This is the end of that Cooler/detectors life. It is scrap.

Best Wishes

Fraser