Looking at the schematic:
Raptor Coil:
- Vio/Yel = 50V, PPB J7, Pin 3
- Brn/Blk = Return, PPB J8, Pin 4
- 1N4001 across the leads
1. You noted if you bring return to ground, coil fires. Removing J8 and connecting Pin 4 in the connector to ground should produce the same result. If YES, then you have ruled out a break in the return wire.
2. Next, check the diode that sits across the coil's leads. Inspect the solder connection - if broken or funky, reflow them.
3. Next, with power off and DMM in diode mode, you want to measure voltage drop across the diode's leads (~500mV is correct range), with black lead on the banded end of the diode, red on non-banded end. If short or open, simply replace the diode, keeping the correct orientation.
PPB:
1. Appears you are getting voltage to the coil via J7, Pin 3, though 78V seems high - this should be closer to 50V, per the schematic. I just checked my OEM PPB - I too read 75V on J7, Pins 1, 2, & 3. Let's rule that out.
2. Look at J8 next:
- Try the simplest thing first - reconnect/re-seat J8 and try to fire the raptor coil.
- Next, look for bad/cold solder joints on the backside of the PPB, under J8, specifically on Pins 3 & 4. If you see any oddities here, I would not repair, rather make a call to Rottendog or the distributor where you purchased to get replaced.
- Next, check Diode, D18 - with power off and DMM in diode mode. You want to measure voltage drop across the leads (~500mV is correct range), with black lead on the banded end of the diode, red on non-banded end (I read 539mV on D18). This is in circuit, so not perfect. You don't want to see a short or open here.
- Transistor Q4, (TIP36C) - look at the solder connections on this device's 3 leads. If any oddities here, I'd also look to get the board replaced vs repaired. Note: I just replaced the TIP36C and Diode on my flipper board - the second time this has been replaced. I'm not sure how to diagnose transistor issues in-circuit, so looking at surrounding evidence might be the best bet: burnt pins, burnt casing, shorted adjacent diode, open resistor, etc.
MPU:
I'm out on the digital stuff. This is when I'd call a technician.
Hope that helps.