ISG Infrasys Elite XR - Power Issue

[7magman]

Scored this guy non functional on ebay and figured it could fix it up. Dead on arrival. Pulled the thing apart, checked the polarity, hooked up bench power. Power? Board is getting power but I'm only getting a trickle of power (<0.2V) out to any of the main board or to the FPGA. Looks like one of the components is cooked on the power board...see attached

Current plan is to replace the component - but I went through and ID'd most of the components (to the best of my ability, mistakes possible) to try and understand the workings. Can anyone help me understand how this board might be regulating power - and if something else might have caused that Schmitt trigger to fail and it's only a symptom and not the cause?
I did see this post:

Pretty much done with the schematic for the interface board.
Any corrections or comments welcome.
I replaced the BNC on the front with a 4 pin Fischer connector and wired it up to the J1 video output and a small DC-DC to convert the +BATT to 5V for the external RunCam FPV DVR. Works OK on the bench. Produces .avi files. The DC-DC is necessary as its internal DC-DC can only take 5.5V max. and I didn't want to load the ISG's 3.3V. BTW the +5V test point goes to J2 and nowhere else.

which tells me the triggers are used for some sort of signal conditioning used in the connection to the FPGA? Unsure if that failure would cause the screen and rest to completely not be functional...

[basecase]

Hello. Did you get the Elite XR with 100K sticker on it? That one strictly uses 10-12V while the version without (just the silver XR) takes up to 15V. There's also a chance the power button might not be working, so do check that out as well.
Lastly, would also help if you could include some pictures of the PCB where the original battery pack plugs into. I think there are some inline 0 Ohm resistors on that board that could have been damaged from dropping.

[7magman]

Sorry should have included more photos, new to the forum. Yes, the camera has the yellow 100k sticker on it and what I assume is the same core as the E/X? 380 based on how the core looks. (ULIS 384?). Serial number ends in HR.
Both resistors show 0.4 ohms on my meter. so nearly zero. I did verify 12V to the power board from backprobing. Both switches showed continuity when pressed.

[cynfab]

Several years ago I got an ISG 100k off e-bay. Sold as non working, but the boards inside were not plugged into each other properly. Easy fix.
I spent some time reverse engineering the NFPA board. Here is the schematic set I came up with.
Might not be 100% complete, but it is close...

[7magman]

Several years ago I got an ISG 100k off e-bay. Sold as non working, but the boards inside were not plugged into each other properly. Easy fix.
I spent some time reverse engineering the NFPA board. Here is the schematic set I came up with.
Might not be 100% complete, but it is close...

Wow.. awesome! An incredible amount of work you put into that.  I'm hopeful to replace that trigger tomorrow...will report back with test results. The diagram should be very helpful for me to verify everything is working as it should via the test points.

[7magman]

Long story short the chip swap was a bust.    Well, nothing worth doing was ever easy I suppose. So I started following the power using the diagrams cynfab kindly provided. I noticed the red power button is only cycling between 5-12V logic when triggered, as opposed to the yellow button 0-12V when triggered. I assume that the FPGA is expecting a full scale trigger to power on?

Can anyone with one of these boards verify the value of R5? Mine reads 500k instead of the 1M on the other button & schematic. I lack the microscope that would be necessary to read the darn thing, if it's even marked at all.  Only thing I could find wrong or different even. Could also just be the new chip got zorked immediately...

 

[cynfab]

Try removing Q4 and see what TP13 does when you push the red button, If the gate of Q4 is only going down to 5V, it will never turn off. Maybe Q4 is bad.
Did you check the gate of Q4 with a multimeter or a scope? Alter replacing the Schmidt trigger if it's output is still not going to 0V it may be oscillating and not a stable voltage.

[7magman]

Took a week to get a scope and some components.
I've replaced Q4, since it was easy.  No change. Attached are some scope pics from both sides of the trigger for both the red button and yellow button. You can see how the trigger output never goes to zero on red, but does get up to 12v when triggered. I don't see any voltage instability but if you folks think of something else I should scope I'm all ears.