My Vernon AE Control Board

[Mir77]

I have a Mt Vernon AE manufactured in 2007 that may need a new control board. Local shop wants $779.
I found one on eBay for $350, but the part number is SRV7000-456, not the SRV7000-330 in the manual. Anyone know if this is a viable replacement part?

History is I replaced blown igniter last season only to have it cycle once and blow. I had the stove serviced Monday and the tech said there is no power in the wire from the control board to the igniter, and determined that I need a new control board as well as igniter. The stove calls for and drops pellets but the igniter won’t get hot.
Please help! Is this even worth fixing?

 

[BigJohnfromCT]

FWIW, my MVAE was manufactured in late 2010 or early 2011 and I'm having some intermittent problems that point to the control board. I was quoted the same cost from the dealer. If it's the board, I won't hesitate to replace it. The MVAE is a great stove and a real work horse. Others may disagree but that's my thinking. Good luck

 

[kappel15]

That is the right number for a control board. They have updated them thru the years. But before you buy one, I would take yours apart and see if the fuse is blown that is inside of it. That would be a reason for no power from it to igniter. And when you install an igniter, make sure to run wires up thru bracket, to keep them out of the way of the auto clean, or they can get shorted out. And they make a wire harness for the igniter that has inline fuses in it, to keep from having to tear apart the control board. My AE is one of the originals, but I have kept up with all the updates for it and my customers. Love the AE. kap

 

[Mir77]

That is the right number for a control board. They have updated them thru the years. But before you buy one, I would take yours apart and see if the fuse is blown that is inside of it. That would be a reason for no power from it to igniter. And when you install an igniter, make sure to run wires up thru bracket, to keep them out of the way of the auto clean, or they can get shorted out. And they make a wire harness for the igniter that has inline fuses in it, to keep from having to tear apart the control board. My AE is one of the originals, but I have kept up with all the updates for it and my customers. Love the AE. kap

So the srv7000-456 will work if blown fuse isn’t the issue and I need to buy the control board? Is the wire harness readily available? Any idea of the part number? I also definitely need a new igniter as the last one is blown with a hole in it.
thanks!
m

 

[Mir77]

confirmed the control board in my MVAE is actually the 456. The fuse looks pretty crispy so I will try that first. Sure hope it’s a $7 and not $700+ fix. Fingers crossed.

 

[kappel15]

And make sure how you put your wire harness's back on the board. Don't mix up the two thermos wires and make sure they are going on the right direction. And be gentle with them. And part # for wire harness with fuses is srv70034-273. Or at least the last time I looked. kap

 

[Mir77]

I replaced the fuse and the igniter only to find the techs did not leave the screw and wingnut. Anyone have any idea what size these are ? Presumably I can pick them up at Home Depot or the like?

 

[kappel15]

It usually is just a wing nut/bolt all in one. should be able to take the igniter to a hardware store to find one. Needs a washer too. kap

 

[Mir77]

Success! Replaced the fuse and igniter and we have fire. So happy not to have to replace the control board at this time. Now I just need to get the igniter wiring with the inline fuse. Any tips on installing that?
thanks again for the help!
M

 

[kappel15]

Glad we could be of help. Make sure you ran the igniter wires up in the slot, to keep them out of the way of auto clean. And when you get the wire harness, you will see how to install it. And another tidbit of advise, when the wire harness from the power supply to the control board, starts getting the white connectors turning brown, it is time to replace it before it shorts out the control board. Stay warm. kap

 

[Mir77]

Re: the above Mt Vernon AE issues, now we are getting immediately blown fuses when replaced in the control board. I added the igniter in-line harness a few months ago and those fuses have remained intact, but the control board fuses continue to blow and need replacing. Any suggestions?

 

[kappel15]

You have a short somewhere in the wire harness for the igniter. Did you make sure you put the igniter wires up in channel when installing a new one, to keep auto-clean from rubbing on them, and shorting them out? Time to trace wire harness from igniter to power supply. kap

 

[Mir77]

I removed the control board again to check the fuse and it was blown but I also noticed the convection blower connection is burned and brown (image of burnt connection attached). Should I replace the SRV7034-219 blower harness? Does this still mean the igniter harness might be bad? The inline fuses in the igniter harness are intact. I’m attaching a photo of the #14 convection blower connection, and the intact fuses in the igniter wire.
Does the convection blower itself need to be replaced?
Thank you!

 

[kappel15]

Harness needs replaced, but what does the connection look like on the board ? Cheapest is to start with the harness. Inline fuses are good, so need to look from there to power supply for a short kap

 

[Mir77]

Harness needs replaced, but what does the connection look like on the board ? Cheapest is to start with the harness. Inline fuses are good, so need to look from there to power supply for a short kap

I ordered the convection blower harness. The connection from the igniter harness at the board looks fine to me. After replacing blower wiring, should I use original igniter wire or the newer one with the in line fuse?
Could the fuse have been blown from the convection blower shorting or is it more likely the igniter wiring that caused it? Should I test with conductivity with multimeter?

You’ve been infinitely helpful for years. I thank you, as I am a novice and I have learned a lot.

 

[kappel15]

I would purchase the inline fuse harness, as saves tearing into control board for blown fuse. I would test all wires but seeing that melted end tells a tale. kap

 

[kastein]

Hi all,
This was one of the few threads I found discussing details of the control board itself on this pellet stove, and it looks like at least one of you have had the same failure that my friend did, the convection blower harness connector burned up. I repaired his board for him as well as his harness and realized I should probably publicize the information so at least people can have their stove repaired for much less by a local electronics repair shop instead of buying a whole new board and harness. The cost of the connectors is minimal. I put together a simple webpage that I have put all the info on the connector repair on, as well as a resistor that burned up on his unit, and will be adding information on any further repairs I have to do as they occur. Here's the page: (broken link removed to http://w1kas.net/bergquist450-15-0031.html)

Feel free to use this information as you see fit. If I missed anything by all means tell me what and I will add it.

 

[kappel15]

Would you be interested in repairing boards if people sent them to you? kap

 

[kastein]

Absolutely, once the one I repaired proves to actually work again, so give it a week or so to hear back from my friend I did it for. I have been on the fence about offering that, but probably will once it has been working properly for a while.

I can repair both the cable and the board. Have you ever seen the combustion blower side of the board fail or only the convection side? I have only been able to find evidence of the convection side failing in this manner. Just wondering if I should bother to start looking up what connectors I would need to order to repair the convection side or not.

 

[kappel15]

There are many variables that can fail on the board. Are you saying you can only fix harness's and connectors? As i have a board that the igniter stays on all the time. Guess what i'm asking is, can you do diagnostic repair too ? kap

 

[kastein]

At this point in time I can only repair convection blower harnesses and connectors... but nothing on this board is particularly advanced hardware wise other than the fact that it is 4 layer and has extensive ground planes obscuring many traces. I can definitely take a look at it, but can't guarantee it will be repairable until I find out exactly what's wrong.

The control circuit for the ignitor appears to be fairly simple (C266, D34, R257, R259, D43, Q87/86, RLY1, single GPIO on the MCU driving all of it, appears to be a standard NPN ground side switch circuit driving the relay winding) but I have not spent more than a few minutes looking at that section yet. Looking at it my first guess would be that either the contacts are welded on the relay or Q87 and/or Q86 is shorted. Both appear to be SOT23-3 HABT2222/2N2222 types.

To truly put these through their paces and verify before return shipping, I would need a test unit furnace locally to use, but if you can describe the exact problem (as you just did) it is very likely I can repair without that. I would be much more comfortable with having a test furnace, naturally. I do not like unknowns.

EDIT TO ADD: Yes, after spending a few minutes more looking at this. C266 is a filter capacitor, it is fed from the power supply input connector at the top center of the board. One diode blocks reverse bias of the power supply being hooked up backwards from forcing the relay on; the other is a reverse EMF snubbing diode for the relay winding. R259 is a current limiting resistor that they have used as a standard design feature in every 12-15VDC powered subcircuit on this board. R257 (I might have the two resistors swapped, I already screwed the cover back on and I'm not taking it off again at this point) is a current limiting resistor that limits current from the MCU GPIO pin into the Darlington pair base. Q87 and Q86 form a Darlington pair that grounds the negative side of the relay to turn it on. As long as the microcontroller GPIO pin itself is not damaged I can almost certainly repair this failure. I would say 90-95% chance. The only catch is that the relay is discontinued on all my sources so I will have to find an appropriate substitute with the same footprint and equal or better specifications, so hopefully it is the driver transistor(s). I would guess 75% chance of the transistor further into the corner of the board being shorted C-E and 25% chance of contacts welded in the relay, just looking at the overall layout of this circuit and your failure description.

 

[kappel15]

Understandable. It may also help you to download an instruction manual, so as to see what each part is called to do, as with timing etc. kap

 

[kastein]

I do have the Mount Vernon Quadra-Fire AE troubleshooting manual, but is there a board-specific troubleshooting guide or schematic available? It sure would be easier than figuring the two 3-phase motor drivers and main MCU area of the board out from scratch, though I'm not too worried if I do have to do that.

I spent a few minutes going over the spares list in the troubleshooting manual and hit $1000 very quickly putting together a list of parts I would need to build a test setup. At that price point it is almost certainly more logical to either pick up a broken stove locally to use as a test mule, or find someone who has one locally and would be interested in free repairs in exchange for the occasional board test on their unit. I am located in Bremerton WA if anyone fits that description or knows of one looking for a new home.

 

[kappel15]

Not that i know of, especially since they quit making that stove. kap

 

[keithjg]

At this point in time I can only repair convection blower harnesses and connectors... but nothing on this board is particularly advanced hardware wise other than the fact that it is 4 layer and has extensive ground planes obscuring many traces. I can definitely take a look at it, but can't guarantee it will be repairable until I find out exactly what's wrong.

The control circuit for the ignitor appears to be fairly simple (C266, D34, R257, R259, D43, Q87/86, RLY1, single GPIO on the MCU driving all of it, appears to be a standard NPN ground side switch circuit driving the relay winding) but I have not spent more than a few minutes looking at that section yet. Looking at it my first guess would be that either the contacts are welded on the relay or Q87 and/or Q86 is shorted. Both appear to be SOT23-3 HABT2222/2N2222 types.

To truly put these through their paces and verify before return shipping, I would need a test unit furnace locally to use, but if you can describe the exact problem (as you just did) it is very likely I can repair without that. I would be much more comfortable with having a test furnace, naturally. I do not like unknowns.

EDIT TO ADD: Yes, after spending a few minutes more looking at this. C266 is a filter capacitor, it is fed from the power supply input connector at the top center of the board. One diode blocks reverse bias of the power supply being hooked up backwards from forcing the relay on; the other is a reverse EMF snubbing diode for the relay winding. R259 is a current limiting resistor that they have used as a standard design feature in every 12-15VDC powered subcircuit on this board. R257 (I might have the two resistors swapped, I already screwed the cover back on and I'm not taking it off again at this point) is a current limiting resistor that limits current from the MCU GPIO pin into the Darlington pair base. Q87 and Q86 form a Darlington pair that grounds the negative side of the relay to turn it on. As long as the microcontroller GPIO pin itself is not damaged I can almost certainly repair this failure. I would say 90-95% chance. The only catch is that the relay is discontinued on all my sources so I will have to find an appropriate substitute with the same footprint and equal or better specifications, so hopefully it is the driver transistor(s). I would guess 75% chance of the transistor further into the corner of the board being shorted C-E and 25% chance of contacts welded in the relay, just looking at the overall layout of this circuit and your failure description.

Just set up an account to reply to this: Amazing and thank you so much! I replaced the relay even though it tested OK, with no change, so proceeded with the transistor fix. Q86 was bad, and replacing it solved the always on ignitor issue. I got the stove used, and luckily noticed the ignitor on issue while testing it for the first time.

Again, thank you very very very much for this info!

Keith G
New Hampshire