AvBaeyer
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Stirre-Hotplate problem
I have a Corning PC-420 stirrer-hotplate which has recently decided to stir at only one speed - very fast - no matter what the setting. Is this a bad
potentiometer/control knob (I am not an electronics person) or are there deeper problems with the solid state circuitry inside the unit? Any hints or
suggestions on how to test, troubleshoot or repair?
Any insight will be much appreciated.
AvB
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FireLion3
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I would contact the manufacturer first before attempting any fix-advice obtained from here first. They may even offer you a free replacement or
repair. Your guesses could be accurate, but there could any a number of causes. The manufacturers may be familiar with this specific issue.
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Dr.Bob
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The Corning hotplates do that sometimes. It may be as simple as a piece of dirt or a big in the optical speed sensor, if that if the way those work.
I would just open it up enough to check for simple issues like that. The manufacturer is not likely to do anything, based on my experience, unless
the hotplate is nearly new. You might be able to find someone at a local college or company who does instrument repair who can fix it easily. Even
the place I work has someone to fix things like that, as we are a non-profit.
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AvBaeyer
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Thanks to both of you for your responses. I will take another look inside and blow out any dust accumulations. The speed control failure seemed to
happen gradually over time. First, the slow stirring speed disappeared for a while, that is I had to turn the speed control to about half way to get
it to start. Then there was no speed control, just fast, at any setting.
I got the thing for free but a replacement looks a bit pricey on ebay. Perhaps I can find one for parts if I am patient. Fortunately, I have some
other options but I really liked this stirrer/hotplate.
Again, thanks for your suggestions.
AvB
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zed
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Hey! Take a walk on the wild side!
Maybe something as simple as blowing a little freon (or WD 40) into the Rheostat will solve you problems.
Open the puppy up, and see what makes it tick.
https://www.youtube.com/watch?v=qEYyQIIGQcc
[Edited on 7-8-2014 by zed]
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AvBaeyer
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Zed,
Thanks! I loved Lou Reed and Velvet Underground (shows my age). Remember the album with the banana on the cover? Just sold mine which was intact for a
nice sum.
I will blow out the internal workings of the stirrer. Went to get my canned air and it was empty. Unfortunately, it looks like a solid state control
system inside so it may be a component problem requiring a board replacement.
AvB.
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aga
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As Dr Bob suggests, it's most likely to be a problem with the speed sensor or the control knob.
If the speed sensor is an optical disc (plastic with lines printed on it) then it will pass through a slot which has a light (usually IR) emitter on
one side and a detector on the other.
If the disc gets dirty, or dirt accumulates in either the emitter or detector, it could do what you're describing. Careful cleaning the disc - you do
not want to erase the radial black lines.
Less likely, but still possible, will be the control potentiometer wearing out.
These can be bought on ebay for a few $ and are easy to replace.
If the electronics are at fault and you're not 'au fait' with it, best let someone take a look at it for you, and/or see if there's a pukka
replacement or compatible available.
EDIT: found this :-
http://www.instructables.com/id/Remove-heating-function-from...
Seems the Disc is a slotted metal disc, so it is most likely to be the Sensor or associated electronics.
[Edited on 8-8-2014 by aga]
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