Odd potentiometer on Oven Control Board

[kgvickers]

I'm helping a friend fix his 1988 vintage Kenmore oven, part number 278.4298891.  Here's a link to a picture of the control board: https://www.repairclinic.com/PartDetail/Oven-Control-Board/WB19X255/247199?model=165267

The faulty part appears to be what I would think is a pot that you can see on the right hand side of the board.  It has "detents", meaning it clicks while turning.  But it has no stops - I can turn and turn forever.

Is there a name for such a device?  I'm trying to source it because it appears to be the only thing wrong with the board.

Thanks,

Keith

[ECtoFix]

8 hours ago, kgvickers said:

The faulty part appears to be what I would think is a pot that you can see on the right hand side of the board.  It has "detents", meaning it clicks while turning.  But it has no stops - I can turn and turn forever.

Is there a name for such a device? 

No, that does not sound like a potentiometer.

What you're describing sounds like what is usually referred to as a ROTARY PULSE GENERATOR (RPM for short), since they generate electrical pulses when they're turned.  They are specifically used in DIGITAL control circuits.  They have largely replaced potentiometers for things such as the volume control of modern stereo equipment.  The ones I see used in COMMERCIAL COOKING EQUIPMENT do have the feel that there are detents as you turn them.  And, YES - they are designed to turn without any mechanical stops.

Usually when those go bad, they will simply no longer "adjust" whatever mode you're attempting to change - whether it be a temperature setting or clock setting of the oven.  Another form of failure is when whatever mode you're attempting to SET with it goes bonkers - evidenced by the digital display jumping up or down uncontrollably or by taking huge leaps when the RPM is turned.

When these things came into use years ago, they were (unfortunately) incorporated into the boards they were designed to be used with.  As such, if just the RPM went bad or got damaged, the whole board had to be replaced.  That was a BAD thing for owners of commercial cooking equipment because THEIR control boards are generally in the SEVERAL THOUSAND DOLLAR pricepoint. In recent years, the ones I NOW see are designed to be separate from the board to allow a much cheaper repair. 

It's unfortunate that the board you need is obsolete.  Hopefully you can source that RPM, solder it in and be good then...IF that's actually your problem.

 

[Vance R]

+1 for rotary encoder. 

Look like a few people rebuild the board. If your handy with a solder iron, remove the encoder. On the encoder there should be the part number and possibly the manufacturer in very small printing.  Google search and you maybe able to find a replacement.

[ECtoFix]

5 minutes ago, Vance R said:

Look like a few people rebuild the board. If your handy with a solder iron, remove the encoder. On the encoder there should be the part number and possibly the manufacturer in very small printing.  Google search and you maybe able to find a replacement.

Rotary encoder?  I'd found that through some more research after making writing post.  Thanks for confirmingt.  I didn't know how else to describe it.

Just don't know why he thinks it's bad.  If it's because of how it seems like a questionable potentiometer for it rotating endlessly and also having a stepped rotation, then those are the wrong reasons to want to replace it. 

Also, we don't know what the real symptoms to the problem is.  If the oven isn't heating, it could also be a bad probe or relay board...which can be determined through further troubleshooting.

 

[ECtoFix]

Aggravating to not be able to edit a post after discovering that I'd fat-fingered, blinked or brain-farted what I wrote.

[Vance R]

The temp display will jump to weird numbers while turn the knob is my guess. 

[ECtoFix]

22 minutes ago, Vance R said:

The temp display will jump to weird numbers while turn the knob is my guess. 

Yup.  Same as what happens on the commercial ovens I work on.  Like this one that I'm ALL too familiar with:

Rational Model 202 Electric Combi Oven - 208/240V, 3 Phase, 68 kW

[kgvickers]

Thanks everyone for the info.

Turns out the part was ok, there were bad solder joints on the board.  It's a really crappy design, the part is stabilized by metal tabs in the housing that are soldered to the board.  The "stem" (I guess that's what it should be called - ??) is threaded so it would have been nice to have a bracket of some sort to hold it in place.