Fried my Fathom S ROV side board. Not sure how

Blue Robotics Products Tether Interfaces
1

I was running a motor with a basic esc, but when I increased the speed the ESC stopped and so did the motor, and my fathom board started smoking and the power light went off. There is no visible damage, but upon plugging it back in(to both 15v and 5v) it began smoking again even without the motor running.

These were the components that started smoking:

LM2776 from the Supply Inverter for Op-Amp circuit

ST490AB from the TTL to RS422 circuit

The fathom board was hooked up to the same 15v power as the motor (in parallel obv) The raspberry pi was hooked up to this power as well via a voltage converter. The raspberry pi’s ground, 5v and rx gpio pins were hooked up to the fathom board in their respective places.

Any ideas what could cause this? If more info is needed I can supply it.

Edit: After plugging the board into only 15v power it turned back on, but the MC7805 component heated up a considerable amount and gave off a burnt smell. (no smoke, and the polarity was correct btw) Also the LM2776 component heated up slightly as well.

Edit 2: It might have been caused by something to do with the pwm controller I am using currently (Adafruit 16-Channel PWM / Servo HAT for Raspberry Pi - Mini Kit : ID 2327 : $17.50 : Adafruit Industries, Unique & fun DIY electronics and kits) if that helps at all

2

If a component gets warm and smokes when initially plugged in, it sounds like it may have been reverse polarity somewhere along the line. It usually takes out the power regulator on boards such as the Fathom-S first.

Sheet 4 of the Fathom-S schematic lists the power supply component numbers. If those show indications of burns, then I suspect reverse polarity.

If you don’t think it was reverse polarity, I don’t really have much else.

3

Just a quick question, does the 5v pin on the ttl serial port supply power out, or take it in?

4

The 5V pin on the TTL port outputs 5V, the TX/RX pins output 3.3V. I measured this morning with a multimeter.

5

Ok, thanks. I know what went wrong. I had 5v power going into the 5v pin instead of coming out. The speed controller must have caused a spike or something.

Edit: because the mc7805 component is broken, is there a way to remove it and just put wire in it’s place?