Fraser has two new patients inbound - E2V ARGUS 4 & Seek Reveal Pro FF

[Fraser]

OK, a before and after picture set from the patients memory........

The ambient in the room tonight was around 24C

[Fraser]

Other pictures taken by someone else before I got the camera.... just look at that noise 

Fraser

[Fraser]

So I found the fault and it was as I had hoped, the output side bypass capacitor on the 2.8V LDO regulator. I was half expecting the fault to remain and the LDO to be faulty in some way but I am pleased that it was just the MLCC capacitor.

This was actually a pretty simple diagnosis and repair...... they are not all so straight forward. The pattern of the noise signal present on the display just shouted "noise injection into the analogue front end" to me, so it was just a case of identifying the power supply rails and checking them. Some other less friendly faults are more challenging to localise and that is where the carefully managed approach to diagnostics often pays off. Diving straight in with a scope and soldering iron is so tempting to do, but is not always the best approach, especially when dealing with relatively high density PCB's and 0402 or smaller components !

That is all for now 

Fraser

[Fraser]

Just as a bit of trivia.... this whole investigation was carried out on our dining room table with simple tools, a relatively simple and inexpensive portable UNI-T UTD1102C DSO and a Fluke 87 III multimeter.

The Pace soldering iron was only brought out to play once I had a good idea what my target was 

You do not need a sophisticated lab to repair many faults on thermal cameras. A methodical approach and simple tools is often enough 

There are the challenges of reworking large SMT devices and BGA types that require more sophisticated equipment of course ! I do not think my wife would let me place my Jovy 7500 IR rework station on the dining table somehow  She can be so unreasonable at times 

Fraser

[Bill W]

As can be seen from the pictures.... normal service has been restored 

This camera had suffered the failure of one tiny 30 Cent component. I have that component safe and will test it. I suspect it has suffered a stress fracture and lost capacity.

Good news 

Surprised the capacitor came off in one piece, usually these cracked ones come away in two parts - at least it makes desoldering easier !

Bill

[Fraser]

Thanks Bill,

I had expected the MLCC to fall apart as well ! I do not know what is wrong with it but a fracture seemed the most likely possibility as we all know how fragile they are. I will put it on my capacitance meter and see what it says about it.

The capacitor took quite a lot of heat to remove it due to the efficient heat sinking effect of the ground plane. I will be removing both capacitors tomorrow and fitting new ones with great care as I take pride in my soldering, even if it will never be seen

Fraser

[IwuzBornanerd]

Congratulations Fraser!  Yet another successful repair as well as a sweet deal on yet another toy you didn't need.     

[Fraser]

The MLCC replacement went OK but the heat sinking copper pour around the LDO regulator is a killer. It was soaking the heat away from the 0V MLCC pads very efficiently and I discovered that the PCB was designed to effectively couple thermally to the alloy chassis. This is actually a nice design that tries to keep heat from the LDO away from the microbolometer. It seems to do it pretty well from my MLCC soldering experience ! 0402 size capacitors, tiny solder pads and a decent heat sinking path makes for interesting rework !

I am a perfectionist and one MLCC is not totally flat to the PCB on the 0V pad so I will be removing it, separating the PCB from its heat sink and reworking that MLCC. No DSO measurements yet as I will do those once I have finished the rework.

Fraser