Sciencemadness Discussion Board

Brand new JJ-1 Over Head Laboratory Mixer speed cntrol not working... Help diagnosing problem please?

LD5050 - 12-10-2019 at 14:06

Brand new JJ-1 Lab Mixer bought on Amazon speed control does not work. Can anyone here help me diagnose the issue? I'm hoping it is just something simple that can be fixed without having to return the thing, which honestly i doubt i would even do. I purchased this specific unit for approx 70 USD here is a link to the exact mixer i bought>

I received the mixer from Amazon in a timely fashion and the shipping container was in good condition so i don't believe shipping has anything to do with the problem. I constructed the mixing apparatus as described by the instructions. Every thing seems to work perfectly except for the most important feature.... the variable speed controller...
I will post pictures of the mixer and what i have going on at the bottom of this post. But anyway, I removed the cover to the main control box to look for a any loose wires or connections but cant find any. One thing i did find are two white knobs inside the control box that control at which point the mixer motor turns on according to the position of the main speed control dial on the exterior of the control box (i can get more into this if some one actually takes the time to read this and has the time to help me out).
I have a multi meter for trouble shooting but i have no clue really about electronics but from what i can see this looks like a pretty simple circuit to some one who has some sort of back round in electronics. Thanks in advance to anyone willing to take the time to help trouble shoot what ever is going on here or even come up with another way to control the speed of the motor.

LD5050 - 12-10-2019 at 14:42

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LD5050 - 12-10-2019 at 14:45

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TheMrbunGee - 12-10-2019 at 15:31

Sorry to read this!

So you are saying that everything works besides the speed control, so does it spin the motor and you can't control the speed or what?

I am not familiar with this kind of machines, but looks quite simple. But to start I must know the exact problem description. What is not working, how it was supposed to what it does instead. circuit looks simple enough to find the problem with multi meter.

EDIT: If the timer works but nothing else, then you should check the fuse.

[Edited on 12-10-2019 by TheMrbunGee]

monolithic - 12-10-2019 at 15:35

Does it spin at all? If you can hard wire the motor and verify that the motor works, start working your way through the rest of the circuit. Test the power switch. If it's on, you should be getting some sort of voltage across it. You can test the potentiometer quite easily, according to some spec sheets you should get 27 ohms to 10k ohms across its range of travel. See

Sulaiman - 12-10-2019 at 16:54

Get a refund or replacement !
You are covered by Amazon policy - including p&p.

Do not mess with the insides - it may invalidate your warranty !

You may end up with a new unit (or refund), plus this faulty one :)
ask again at that time.

P.S. My general policy for Amazon or eBay purchases is;
test - if faulty immediately ask for replacement.
You may have to post the faulty item back - ask for a prepaid postage label.
Often the postage costs cause suppliers to not want the faulty unit returned,
in which case you end up with the faulty unit (to mess with or attempt repair) AND a new unit or a refund.

If the item works then optionally open it up and check for poor assembly and rectify.

[Edited on 13-10-2019 by Sulaiman]

andy1988 - 12-10-2019 at 17:17

Once I bought a "top-shelf" ATX powersupply, but one of the wires critical to its function were not crimped into the molex connector properly, and it was hours of pain to get it in there.

Check the resistance of each of those wires, across the connector, onto the other side of the board or to whatever is accessible.

That'd be my first guess as to what the issue may be.

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Quote: Originally posted by LD5050  
One thing i did find are two white knobs inside the control box that control at which point the mixer motor turns on according to the position of the main speed control dial on the exterior of the control box (i can get more into this if some one actually takes the time to read this and has the time to help me out).

Or that, sounds like some sort of calibration. I'm not familiar with those and I'd expect that to be in a manual.

[Edited on 13-10-2019 by andy1988]

LD5050 - 12-10-2019 at 17:53

thanks for all the replies this is great. My father who is good with this kind of stuff, after giving him a brief description over the phone, thinks its the Rheostat also called the potentiometer i believe. I'm wondering if i can pull a rheostat/potentiometer out of some other common appliance and switch it with the broken one.

Yes the motor does spin at a high rate of speed when i turn the unit on and twist the speed control knob clock wise and when i turn it counter clock wise until it cant turn any further the motor will shut off. So its either i get the full RPM of the motor or i get nothing.

SULAIMAN, after thinking about it i have changed my mind and i will put in a complaint to Amazon and maybe i will end up with two! but if not yes they will definitely replace this broken one.

The Rheostat has the following stamped on the back in blue ink: WX110(010)
Does anyone know of a common household appliance that would have this or one equivalent that i can substitute it with? possibly a ceiling fan speed control knob ?

picture of rheostat

LD5050 - 12-10-2019 at 17:57

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Sulaiman - 13-10-2019 at 03:59

A new one is not too expensive

but first check the potentiometer using your multimeter on the Ohms range, with the connector removed from the pcb.
2.2 kOhm +/-5% between the two outer tabs,
almost zero to 2.2 kOhms between the centre tab and either of the outside tabs as you rotate the shaft.

As it is a wirewound potentiometer you should be able to feel and hear the wiper moving across the resistance wire turns,
it should be smooth and consistent.

Try the same measurements at the connector end
(you may need to wrap some fine wire around your meter probes and poke the ends of the wires into the connectors)

phlogiston - 14-10-2019 at 02:19

There are two adjustable resistors on the mini board (mounted upright) two which the rheostat is connected, one on either side of the connector. These presumably form a voltage divider with the rheostat.

The behavior that you describe could be caused by a wrong setting of one or both of these adjustable resistors. In that case, nothing is broken. You would only need to adjust the setting of these resistors.

However, I think Sulaiman's advice is best. Get a replacement first, and then fix this one. It looks simple indeed, I think it is definitely doable to fix it with our help.

OldNubbins - 14-10-2019 at 10:07

Sounds like an issue with the trim pots. I attached an image with a circle around a bad solder joint on one of the pots that could be the culprit.

Capture.JPG - 52kB

LD5050 - 15-10-2019 at 15:46

Thanks for the replies everyone. I ended up just scrapping the control box/unit what ever you want to call it and i improvised a "potentiometer" for control of the motor by taking apart an old battery powered drill and using the trigger assembly. I hooked the drill battery to the trigger assembly and then to the mixer motor lead wires. a simple pipe clamp around the trigger to adjust and hold the position of the trigger therefore controlling the speed of the motor......:P

I know... very micky mouse setup but i needed it in a hurry. I will being filing a claim with Amazon but now that i totally detroyed the thing im not sure they will send me a new one. Or will they? im not sure how Amazon works, my wife actually ordered this for me as a gift. I would assume Amazon would want me to mail the original mixer back first then send me a new one? Oh and i will post pictures ASAP of my nightmare set up if anyone is interested.

G-Coupled - 15-10-2019 at 18:15

Aaargh, what a waste, dude! You could've checked the pots with a $10 multimeter and figured it out. I mean - bravo for McGuvering whatever that thing is, but minus several million for 'Green Chemistry'.