EEVblog #401 - Lecroy 9384C Oscilloscope Repair - Part 2

Dave brings out the big guns in this attempt.
Can a $12K Flir E60 IR Thermal Camera find the fault?
Once again, a "real-time" attempt to find the short on the Lecroy mainboards 3.3V rail.

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[ArieLash]

I love your Video's but I feel I must comment on this one
1. When looking for a short like this I never allow the voltage to go over 0.7 volts. In my view you blew the asics by power up the 3.2v
without the higher voltages.
The problem is called power supply sequencing where the first psu
needs to be the highest voltage to the chip.then each lower one in sequence.

[googacct]

While the second ASIC may only be a few degrees warmer than the others, how much extra power is required to drive that heat sink the few extra degrees above the others.You may find that the extra 15Watts that is being used is going through that heat sink.

[Aistlander]

I was really surprised when Dave showed that the Flir was made in Estonia. I'm an Estonian and I didn't know that Flir has a factory in my home country. Estonia is a very small country (1.3 million people) and it is very cool to discover a shred of it from a video of world-renowned Australian Dave Jones:). Now I found out that Flir was a nominee for the 2016 Foreign Investor of the Year award (didn't win it though).

[FyberOptic]

I was actually excited to watch this one when I saw you decided to do a follow-up. I really like these diagnosis videos. Though it bugs me a little that you didn't whack those chips off one by one to see if that got rid of the low resistance. Even if it's dead, it'd be nice to know for sure!

[Ruskotyara]

Hi Dave
I think ASICs are good. It's normal working temperature for them. They are highly integrated and they consume a power. I think problem is "COLD SPOT(S)". One or several points have oxide contac(s) or which is very probably "BAD SOLDERING" wave. Point(s) is somehow connected with ground so all power you take in ground suck. Somewhere is a closed loop with ground maybe directly maybe through some diode transistor or ic(s). Best you can do is to put good soldering flux and reflow whole PCB

[LocoAullador]

I'm sort of a beginner in electronics but I'm in love with that thermal camera. I don't know how usefull it might be right now to me but it's totally cool. I feel like I need it xD

[MC-Racing]

isnt 80 degrees quite hot for a semi conductor. i know all four chips are at the same temp, but my guess is that it IS those chips that draw all that current!

[ImaginaPower]

I´m still wondering about the melted relay?!!!

[mikeselectricstuff]

I'd be unsoldering the hottest ASIC

[montinhoman]

Dave, I don't think the heat you see on the BNCs are reflected heat. Look at the numbers in the screen, it just autoranged ( this is clear when hotter things are on camera too, like the heatsinks @31:18 or your finger @30:38 )

[JGunlimited]

Was wondering why the Flir camera was not the first thing used (in this video and the previous)! Then I saw the date of the video, and heard the price at the time. Lol, how things have changed.

[Volta]

It would be interresting to see how the 'scope would cope when powering the short 3V3 rail With your high current PSU.
Connect everything back up, power the 3V3 rail with the HC PSU and see what happens.

[SwitchingPower]

The thermal camera's freeing some times is because of the internal calibration of the sensor array using a shutter with a known temperature.
Also the FLIR E60 can take movies and output a live video stream via usb and composite video.

[seephor]

I think that temp difference on that one heatsink is very significant. You're looking at temperature dissapation through a heatsink so unless you remove the heatsink, you can't really assume everything is ok. I suspect it's a chip under that one hotter heatsink

[darrylmay]

Probably suggested before but use a thermal insulator such as a bit of plastic or foam to prevent spill from affecting your thermal readings.

[azyfloof]

What a total bummer, all that hard work! Always gets my goat when I have a dead bit of kit that I think is gonna be an easy fix, and it turns out not to be the case :(
I definitely agree with others who suggest taking off that slightly hotter ASIC and seeing if that makes any difference at all.
Also do a surreptitious tear-down of the FLIR for Tear-down Tuesday on New Years Day ;)

[wooxk]

Reassemble it and fire the board up with high current supply to see if and how much does the thing work! Nothing to lose at this point and then you could actually know if the supply took the board or board took the supply. (It worked before supply died and we don't know how much current it was taking before it happened)

[EEVblog]

Do the math. 0.5V would only be about 2.5W. And the chips have large heatsinks.
Anyway, I tried it, and zip. Same temp on all heatsinks (a few decC above ambient)

[TheOriginalEviltech]

Good idea, but cmos devices tend to work even under 0.1V
I say remove that ASIC and test again. Sometimes when power rail on power supply fails it takes out other stuff on the board too. The board might even start without it. it's function will be impaired, but if this is it the scope will power up.

[douro]

You ought to consider a basic thermal camera for your lab; an Extech/FLIR i7 would be more than adequate, even though it's only 140x140 resolution.