One question is how bootstrapping the relay is supposed to work. The base of Q3 needs to be pulled negative to allow current through the relay coil. This is done by Q6, but before the relay closes, there is no power on pin 6. The emitter of Q6 also connects to pin 8, but the base will only turn on if pin 8 is positive with respect to... pin 8. Maybe there is an internal connection on the panel board that makes it possible.
First of all thank you so much for your participation
I have learned so much about electronics in past few weeks.
It did not make sense to you because of me making errors in tracing out the pcb
...there might be more.
The pinout I believe is like this. I have verified 1, 2, and 3.
1&2: Ground
3: Standby 5.1V
4: AC frequency input?
5: Hall Effect sensor
6: Active Ground from Main pcb??
7: PWM out
8: relay control
I have removed ZD2 and put ZD3 in its place. At pin 3 read +5v and pin 2 as ground. But R12/R23 still get to 250F. The only thing left is is C9 and ZD1. However, a while back in post #3, I removed everything except those pair of resistors, a diode, the 220uF main cap, the 4.6k current limiting resistor and the 5v zener. The R12/R23 still got hot. This only leaves the cap that I have not replaced. I checked its capacitance using UT210E and it reads .265mF. If I remove the zener then the R12/R23 are barely warm.
Question, could it be normal for R12/R23 to run hot at 150F in this circuit with 30v zener and then 5v zener clamping down? Perhaps with original D8 that showed 1.6v in reverse caused the R12/R23 to get super hot and that's what cause discoloration to PCB? Now with new D8 its ok?
Next I need to probe pin 8 and see if its being pulled high, then check if Q6 switches on.
I put together the panel schematic now. If something don't make sense, plz tell me, I will retrace.
Does this thinking sound valid about the workings of the Panel circuit?
- The PIC powers up and sends +5v to all the function switches and all the LEDs.
- Pressing a function sends +5v to pin 8 that drives Q6 on main pcb, also Q4 that grounds pin 13 of Micro.
- PIC pulls pin 3 high which switches Q5 that gives Active ground from main PCB for LEDs??
- Pressing OFF shorts out +5v and Active ground from main PCB which causes PIC to reset
[/list]
Panel
Main