Harman P61A-2 , 100K POTS

[Delargy]

Hi New to the forum. Have been reading and learning for a couple days now. Thanks for the info.

Trying to find new 100K POTS for my Harman P61A-2. Stove works exactly as it should in Stove Temp. In Room temp/Auto as I turn it on, the combustion blower and light come on for a split second, then off. Also no status light.
In room temp/manual as I turn it on, the combustion blower and light come on as normal waiting for the pellets to be lite and heat up. Status light also comes on.
I lite the stove in room temp/manual, everything worked fine but the stove stayed in a low burn. Even when I turned temp dial and feed dial to max. Switched to Auto, stayed in low burn.

New ESP, room sensor and ignitor installed with no change. All motors have been cleaned and run independent of stove. Stove worked great for 9 years, then this when trying to start up.

All help would be appreciated. Also when removing POTS, do you melt solder from back of the board. A short description would be great.

I know, a lot to ask from a newbie, but my wife is cold in the basement

 

[Bioburner]

The project of removing the pots and reattaching is not a project I would tackle without having a fair amount of soldering experience as one could delaminate surrounding circuits and toast the board. The tabs are also bent to help hold them in. Yes to soldering on the back side.
Have you a computer and or cell phone repair shop? They can easily do the job
Have you traced the room temp probe wiring from the connection on the back of the stove back into the board or bypass it completely and hook the probe directly to those wires coming from the board?

 

[Delargy]

Thanks for the reply. I have traced the wires back to the board. Disconnected from board and tested. 3.88 was the reading. not sure if milli ohms or ohms. I will try connecting room sensor direct to the board. What reading should I have on that sensor? Thanks

 

[Bioburner]

I don't know the value as it would be variable with the temperature. Hopefully someone with more tech experience can chime in.

 

[MarkF48]

The manufacturer appears to be ACP http://www.acptechnologies.com/catalogue/potentiometers/ca14-ce14/

A US distributor is Vimex http://www.vimex.com/tpots/pages/TPT-CA14-index.htm

Besides the 100k spec, the taper (how the resistance changes during rotation) needs to be known which would be part of the entire part number.
http://www.acptechnologies.com/catalogue/potentiometers/ca14-ce14/ca14-ce14-tapers/

The basic ACP P/N appears to be CA14 VD11, but the full part number would need to be known to order the correct one. I haven't seen an image of a Harmon circuit board that shows a P/N on the pot, only the 100k value. Not sure if the knob is integral to the pot or just is inserted into the hole.

I can't say I've ever run across this manufacturer in all the years I've been repairing electronics gear (mostly audio and music related). There may be an alternate pot from Bourns, ALPS, or other but the dimensions and electrical specs would need to be pretty much identical.

If the pot is intermittent, possibly a squirt of DeOxit Fader Lube might clean it up depending if the cleaner can penetrate into the resistive track and wiper. Works well on noisy/scratchy audio pots.
https://www.amazon.com/dp/B00006LVF1/?tag=hearthamazon-20

If you need to ask how to desolder the pots, you probably shouldn't

 

[Delargy]

"If you need to ask how to desolder the pots, you probably shouldn't "

Sound advice for sure. heard people say it is easy, BUT could screw up other parts of the board.

 

[Mt Bob]

Buy a can of electronics cleaner spray,with the little tube,spray the pots liberally while turning shafts.May get you by for a bit,and help diagnose it is the pots.Trying to pick out the proper pots from vimex is a pain,and generally only sell in bulk.Buy them from the guy on ebay,a bit more,but the right ones.

 

[Delargy]

Thanks. Tried the electronics cleaner thing. "Nuthin". Anyone have any other thoughts on what this could be other than the Stove temp/Room temp POT. Can that POT go bad on the Room temp side and not on the stove temp side? I have always used the stove on room temp. Just wore out on that side??

 

[Bioburner]

Yep, someone posted the number of swipe cycles those pots were to have and it wasn't that many.

 

[MarkF48]

Took a measurement of the 'room sense probe' on my XXV at the terminal ends. 4.0kΩ at a temp approximately in a range of 64-66F degrees. Your '3.88' (3.88kΩ) was likely in the ballpark depending on the ambient temp.

 

[Delargy]

Thanks. I had my wife hold it in her hand, the reading changed rapidly, so I thought it was working. Another POTS question. The Stove temp/room temp POT has an off position in the middle of the swipe, Is this a different one than the other two on the board?

 

[Mt Bob]

Thanks. I had my wife hold it in her hand, the reading changed rapidly, so I thought it was working. Another POTS question. The Stove temp/room temp POT has an off position in the middle of the swipe, Is this a different one than the other two on the board?

Your wife prob had her fingers touching metal.Nope,all pots the same,the programming knows the off setting

 

[Mt Bob]

But a new board is 200 bucks,buy one now,tinker with old one later

 

[Delargy]

But a new board is 200 bucks,buy one now,tinker with old one later

Thanks for the info Bob and everyone else. Yes I ordered a new board, along with 3 new POTS already. I will be an electronics whiz by the end off this process ???? maybe. LOL . Will have a spare board at least. Package will not cross the border for a week or two. I will post the results. good, bad or ugly.

 

[Mt Bob]

Thanks for the info Bob and everyone else. Yes I ordered a new board, along with 3 new POTS already. I will be an electronics whiz by the end off this process ???? maybe. LOL . Will have a spare board at least. Package will not cross the border for a week or two. I will post the results. good, bad or ugly.

Oh crap,you are up there!If I can ever help you on shipping,let me know.Sometimes things can be packaged down here and shipped without the stupid taxes.

 

[Delargy]

The taxes are not bad. Its the exchange rate that hurts. Costs us about 33% more right now. You should come to Canada for a vacation. 33% discount because of the exchange rate.

 

[Bioburner]

The taxes are not bad. Its the exchange rate that hurts. Costs us about 33% more right now. You should come to Canada for a vacation. 33% discount because of the exchange rate.

If I could bring enough gasoline. Your gas is insane high or maybe its the taxes? Wouldn't mind getting some decent bulk tea. Seems all I can get here is bagged

 

[Delargy]

Yes, you are right. Tax on gas is goofy. About 50% of the price is taxes. Today we are paying about $4 Cdn per US gallon. With the dollar exchange it would work out to about $3 US per US gallon.
Nothing but Red Rose for me.

 

[Bioburner]

Red rose only available bagged and that is painfully weak so have to double up. Might well be older stock

 

[Delargy]

Well, got my new board installed. The stove works as it should in both room temp and stove temp modes. I also got 3 new 100k POTS to replace the ones on the old board. Specifically the room temp/stove temp POT.
On the new board the RT/ST POT has a distinct off position in the middle of the dial swing. You can feel a slight click when it hits the off position. The other POTS on the board do not have this stop position. I asked this question before, but, Are the three POTS on the board inter-changeable or is the RT/ST POT of a different configuration???
Thanks

 

[Bioburner]

I have done three boards and no issue with interchanging. Carefull and good luck with the soldering.

 

[Delargy]

Thanks. I found an electronics shop in town who will do the soldering. I can do copper pipe like an old plumber but my torch may melt the whole board LOL.

 

[Bioburner]

I purchased a digital control iron and has paid for itself several times over that and it was on sale for $40.
You can set for the exact temp and know when it has been achieved.

 

[D_Freeman]

I have done three boards and no issue with interchanging. Carefull and good luck with the soldering.

Where did you get your pots for the repair...from E-bay? I've been having the same issue with the pots and decided this year I was going to fix my stove. I have a hard time paying $15/pot when I can get the pots from PS components for $0.54/pot. I have removed one pot and determined that it is the CA14 VD11 with a linear taper and an "N" type rotor design. This particular pot uses a dozen different rotors. Unfortunately...like mentioned in this thread...I'll have 147 spare pots that I can sell. BTW, if removing an old pot that you don't want to save...cut and remove the pins 1-by-1. Ultimately you want to protect the board from heat damage.

 

[Ssyko]

the new pots are CE14NVD11-100K