whitfield pellet stove

[flinchy69]

If I told you I'd have to kill you....... Lol seriously we use them where I work as a lowie(sp?) to exammine crystal planes. But got permissin to throw this in for a quick look. It would be hard to do point to point without exposing circuit like I have,but this gives you an idea. I am in the process of mapping it and will post an updated photo of pic #1 soon. You will note pins with traces that go nowhere or the transistors with floating (base?). I was hoping someone w/ more smarts would recognize what they are doing with this circuit and post their thoughts.......
Stay tuned!!

[haklesup]

The four red components are diodes and judging by their size and layout I would guess form a full wave bridge rectifier with the two left pins as the supply.

Another component probably another rectifier diode is missing. It has the same x-ray appearnace as the other diodes. I'm guessing something in the 1A range maybe s 4004 or 4001.

I see places for 2 transistors. Most likely NPN because these are favored in many designs ( a good guess would be 2n2222 or similar). The heavy black lines on the substrate are resistors, I see 5 maybe 6 of them. Finally I see a smaller diode top right and a capacitor just below it. Thats it, no active components like ICs anywhere to be seen.

Reverse engineering the circuit shouldn't be too hard except that the resistors are badly scratched and may not be possible to measure their values. With a schematic and good guesses at values, it should be possible to make a replacement module.

[flinchy69]

There isn't a resistor one on this board. I think your mistaking black marks as resistors. My thought is that they were used to line up pick and place machine when it was populated. There is no continuity across those points at all. If i'm wrong I'd love to have some light shed on it. I have the main part of the controller drawn out and will add some of the main components when I upload revised pic.

[jwax]

I'd agree with haklesup- those are thick film resistors on the board. Crank up your ohmmeter scale to read their value.

[flinchy69]

Yup , right after writing last post I verified I was wrong. the trick to measuring is to not push hard with the probes or I punch through. Unfortunatly most of them are damaged from the dremel when I removed epoxy so it will have to be a guess I think. But I have values for a couple.

[flinchy69]

Ok here it is:



the 2 resistors to the diodes are 100 ohms ea. The resistor between grey and pinkish purple measure ~1.3 meg. All others ????????? pins are #'ed 1 -10 left to right. #1 is pin2 of triac externally #2 is pin3 of triac #'s 4&5 have 22 uf electrolytic w/ #5 being positive #6,7,8 have fine tune trim pot w/ #8 being the wiper.

Tomorrow I will stick this in an electronic micoscope. Although the resistors didn't show up in xray, if they are carbon based they will glow like a light bulb and I will verify a couple of spots that I think might be there but am unsure of.

Perhaps this is starting to look like something to someone?

[flinchy69]

Ok so I took the module that I xrayed and made some measurements. I then did a little careful coring as to not damage circuit any more then needed to get the remainder of the info that I wasn't able to get with the bare board.


So with all my info patched together I come up with a schematic that looks something like this:

Now there could be a mistake and if you find one please feel free to point it out and I'll update the file.
Heres something I stumbled on while poking around. It seems ICM used different trim pots on their main board, don't know if it was what they had handy or what. But I have some with 100k trim pots and some with 50k trim pots, heck I even have one that has 50k trim pot on combustion blower,while having 100k trim pot on convection blower. I mention this only because the resistors are different internally for the corresponding trim pot. I have listed both part values, with the 50k trim values in parenthysis'. I measured the surface mount cap to be 97 nf which is more then likely 100nf with tolerence. One transistor is definatly pnp. I think the other is probably npn opererating in the circuit in a push pull configuration.
I also guessed on the top 1m(500k) resistor on pin 6 as I couldn't measure it. But it physically looks painted the same size and shape and a divider network makes sense there to me.

so there it is guys........... if someone can explain how it works I'm listening. I've also drawn out the main board but won't be posting that as it is something that you can do for yourself. If you can't then you shouldn't be messing with it in the first place as the high voltage can easily damage you or your equipment. Good luck!!!!!!

[kevenjoo]

There is a good supply of what seems to be good quality Whitfield Pellet Stoves at different sites online if you wish to purchase a used one instead of a new.

[Marcdaneau]

I too have a dead Whitfield Advantage II pellet stove with a defective controller board ( the old rotary knob style). The auger motor would not turn. I have determined the Triac is shorted and replaced it. Also a resistor to the Triac has burnt up and is unrecognizable. I guessed at a 820 Ohm resistor. Now the auger motor runs all the time. The input to the Triac is also shorted. This is a feed from another transistor. So far I have been able to troubleshoot it when I can identify it. Currently I need to know the resistor value and to source the other transistor. If I can not find these I think I will inject my own 5V squarewave signal to fire the Triac. Can anyone help me with this. Maybe I could help you?

[flinchy69]

give me ref designater and I'll give you the value

[Marcdaneau]

There are no reference designators. This is an old board with no unit reference designators at all on the pcb. Here is a pic of the unit. I am having trouble sending a pic. The resistor is directly centered in front of the Triac and the transistor is directly behind the resistor. I could send a pic via email. My email is [email protected]. Any help would be greatly appreciated.