Circuit Repair - 44 pin Microcontroller Expected Heat Output?
I am working on a Bluelab Guardian a TDS and PH monitor for aquariums and hydroponics. Total device power is 5v 1 amp. I suspect the previous owner hooked it to the wrong power supply and fried it. No response when supplying the correct 5v 1a
No visible damage on the PCB to make things easy. Many parts of the circuit have active voltage when plugged in which gives me hope it's not a total loss.
While checking the board with power supplied I noticed that the main 44 pin Microcontroller was getting quite hot - measured as high as 170F which seems high to me for such a basic chip.
This chip's model number is "PIC18F2423" - and trying to search through the documentation I couldn't seem to find anything about expected operation temperature so was hoping someone with general knowledge of basic chips like this would have an idea if that level of heat output might be an indication that it's fried. Any thoughts?
Since it stores the programming, if it's dead then there's nothing else I'd be able to do with this circuit so this seemed a reasonable place to start.
While investigating the circuit I did find a DC to DC converter which seems to be dead - has 5v coming in and no output. It's a 4 pin model with no "enable" pin so I believe I should have voltage out. I can definitely replace it just don't want to start swapping components throwing good money after bad if there's a chance the main microchip is fried.
Any advice or suggestions appreciated. Photos of the circuit attached.
@salient the temp for the PIC18F2423 is as follows:
Absolute Maximum Ratings(†)
Ambient temperature under bias -40°C to +125°C
Storage temperature -65°C to +150°C
Also 170deg F is toasty it should still survive this. I would be concerned about having short in that IC circuitry
Check your DC-DC converter D01-01. Looks a little cockeyed but could just be my old eyes
Thanks for the input!
Yes I probably wasn't clear in my original description but I'm confident that DC-DC converter is bad. It is cockeyed because I bent it up just to make sure it wasn't in any way loose and to make sure it wasn't hiding a 5th contact point.
I have 5v coming in on the left set of pins and nothing on the right set with no "enable" pin which I believe is sometimes on these converters, so it at least is bad.
I believe it's feeding a sub circuit which goes to the PH meter but haven't been able to verify for sure. Would the main microcontroller likely be able to go into a fail state if a component in a sub circuit like that is bad?
Any suggestions of what I could test with a multimeter to have an idea if the micro controller is or isn't functional?
I have voltage on most of the sounding contact points near the chip.
I guess I could try reading through the specs to try to see what's normal on each pin, but I'm not sure I have the hand eye to reliably test each pin.