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2025-07-11: I got handed a circuit board from a Country Boy Winslow PI40 Pellet Stove. The complaint is that the selector switch does not function at all and the unit does not turn off.
The first step is to attempt to find a manual for the stove. (PDF, 40 Pages, 1.71MB). I didn't read it carefully though. I also neglected to take images of both sides of the circuit board as well. You'd think I'd get in the habit of doing this, but I tend to only realize a problem is/was interesting AFTER I'm finished with the task.
The first part that caught my attention was the PIC controller, labeled "008 V5.00". I did pop it from the socket and attempt to read the contents. The security bits were set and reading the contents the easy way is disabled. The actual IC under the label is a PIC16C61A; It is a small RISC CPU with exactly 35 instructions and 1K of EEPROM. If I got the right spec sheet, it should have exactly 36 bytes of RAM. I know I'm spoiled with 64GB of RAM on the PC I'm writing this on, but I'm not sure I could fit a useful program in that amount of space! Foreshadow: There are a couple pins that give a hint as to the problem on this board. There is one pin bottom-right to the U2 designator. Also take a peek at the D5 connections - one is not like the other.
U3 appears to be an EEPROM of some sort; It is labeled "ATMLU506", but there doesn't seem to be a datasheet for this IC. I did not remove this IC or attempt to read it. It appears to be directly wired to a 6 pin phone cord-type socket on the bottom of the circuit board. You can see more pins with problems in this photo.
I started noticing some problems with solder joints at this point. The components on the top didn't seem to be soldered properly and there appeared to be cracks in the solder on the bottom of the board as well. (see red arrow as an obvious problem pin.) If you look carefully at the left pin, you will see cracks in the solder if you look hard - they shouldn't be there at all!
Same problem here (red arrow). You can also see other pins with bubbles and lack of solder 'adhesion'.
And here as well (red arrows)
At this point I began to resolder pins where I saw problems. (green dots are completed; red dots need help; View from the top of the board). I tugged lightly on some of the parts, including D3 which pulled free from the existing solder joint. It was not the only part that was this way. I now knew I had to resolder the whole board. This solder did not melt properly or adhere at all. Flux did not help. Old solder had to be removed and completely replaced. After this was done, I needed to test the board, but did not have the stove to test it. I tried to reverse engineer the board to figure out what went where and got frustrated because I *could have* done it so much easier when I had parts off the board; even simple photographs would have been nice. (for some reason I never think of this when attempting to solve a problem...)
IF I had bothered to read the manual a little more carefully I would have noticed this handy schematic. I was able to jumper past the proof of fire, blower, overtemperature & lid switches. Suprisingly, this little board is smarter than I expected. It actually monitors voltages coming from the motors & ignitor and knows when there is an 'open' motor by sensing that the output pin is not being pulled down to neutral. I didn't have the motors to get past these checks and didn't want to overload the board in any way by using random motors I had laying around. ( I guess I could have looked up the parts for this stove and noticed the blower is a Fasco U21B [about 1 Amp] and the auger motor is a simple exhaust fan motor [1/2 amp]) I handed the board back to the customer and asked them to test it after explaining what I did. About 2 weeks later, he let me know that it appeared to be working properly now, although he didn't run the board through a complete heat cycle to double check everything. It is the middle of July after all!
And so, we hopefully are at the end of this little saga... If it comes back again, I'll hopefully get better images and expand this little page. Until then, many happy repairs! (and check your solder joints!)