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ISI Vision3 Image Problem: always changing between Black Hot / White Hot

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HB9HUR:
Hello Everyone
I'm from Switzerland so in advance my English isnt perfect.

Now to my problem I was able to purchase a defekt ISI Vision 3 Thermal Camera on ebay.
First I tried to start it with 6V because that's what the old batteries had written on them. It startet for like 2seconds and than shut down. I than open it up to have a look at its insides. I tried starting it a few times than than per coincidence I felt that a tantalum smd capacitor was a little to warm.
Which I than replaced. After that the start up was still wonky, than I found out that with 6.7V I have the most success. After I showed it a friend who knows electronics, he meant I should but a 1000mircoFarads condesator parallel to the 6.7V power input.
And than it finally started and worked surprisingly good.
But now out of now where it started to change between Black Hot / White Hot with the frequency of the chopper wheel. I retraced the analog out back to the Raytheon board on which it also looks the same so the problem isnt in the post processing side. And now im hardstuck I read about 100 posts here searching for a similar problem but its seems i'm one of the first. 

Here is a video of its current state.

Start up video:
https://youtu.be/LE_qvKfzUG0

More or less clean analog video which ran through an 2003ish Panasonic DVD player and than captured it with my Blackmagic design Intensity Shuttle. Here you can clearly see how it always changing between Black Hot / White hot.

https://youtu.be/XP9HZexhf08

Here in this Google Drive are more Pictures from the disassembly:
 https://drive.google.com/drive/folders/1dsrjLtpKz_IUvKlWptUCu2EEtvB6rm82?usp=sharing

Thanks in advance for every input you guys have.

Bill W:
Start with the good news - it sees hot things !! :-+

Note all BST take a lot of current to start up as the Peltier gets the sensor to temperature, as well as filling all those tantalum on the PCB.  A common fault was the tantalum not being surge rated and going pop - so a good swap out.
I'm surprised you get away with 1A 6.7V. would expect a bit more.  Are you current limiting ?

The video looks like the chopper wheel running at the wrong speed - probably too fast because it is not getting the right feedback from the position sensor.
It might be reflective (with a bright dot on chopper wheel) or transmissive (with a notch on edge of the chopper wheel)

Has the sensor been knocked ?
Has the bright dot fallen off ?
Can you scope the position sensor output ?
Have you got a bright light shining in there ?

Bill

HB9HUR:
Hello Bill

I am not current limiting.

"Has the sensor been knocked?"
Not that I now of. I renewed the thermal paste behind the sensor but that was already after the Black Hot / White Hot problem.

"Has the bright dot fallen off?"
It's a transmissive copper wheel with two diodes.

"Have you got a bright light shining in there?"
I just tried with no light and flashlight Right at I didn't see a difference.

"Can you scope the position sensor output?"
I'll try that next.

Regards
HB9HUR


HB9HUR:
In this first picture i measure with 5microsec and 10mV per square I think this ist something like the "sending signal" side.
 P1030256.JPG (2676 kB. 4000x3000 - viewed 20 times.)
Here I measure 4.95V DC on my Multimeter.

Here I measure with 10microsec and 20mV per square.
When I touch the copper wheel to slow it down a bit you can see it on the oscilloscope. So I guess it's the receiving side.

https://youtu.be/b4h4rr3nn_4

Here I also measure 4.95V DC on my Multimeter.

I'm an amateur so I don't really know what i'm looking at. ???

With my Laser speedometer I'm measuring somewhat around 2850rpm on the edge of the copper wheel.

Regards HB9HUR

Bill W:

--- Quote from: HB9HUR on January 08, 2024, 07:20:35 pm ---"Has the sensor been knocked?"
Not that I now of. I renewed the thermal paste behind the sensor but that was already after the Black Hot / White Hot problem.

--- End quote ---

I mean the position sensor for the chopper wheel - not the thermal sensor IC.

[/quote]

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