LookingForAnswers
Harmless
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Registered: 25-3-2024
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I cant find a problem of my heating mantle
you brothers. as in the topic. I have a problem with the heating jacket. when I turn on the heating, the fuses blow. in the past I poured a water
solution of MeNH2 on this coat, but once I dried it everything went back to normal. this time I hadn't used it since October 23, everything was packed
up with the rest of my equipment and I was waiting to find a new place to continue my hobby. Yesterday I tried to turn on the heating mantle and the
fuses immediately blew. I thought maybe water got inside, but everything was dry. in case I heated the fiberglass with a heat gun to make sure it was
completely dry. I put everything back together and... again... anyone had a similar problem? How could I solve this? I don't have money for a new
mantle right now
Chemistry Pope
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Sulaiman
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Model number, photo's?
Diagnostics/repair may be difficult without a multimeter.
Got one? buy one? borrow one?
Even the cheapest dmm will do.
CAUTION : Hobby Chemist, not Professional or even Amateur
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LookingForAnswers
Harmless
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yes of course
Brand: Vevor
   
Chemistry Pope
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bnull
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It looks like a short circuit. It may be inside the heating element or on the circuit board. It may even be a broken triac (those things attached to
the heatsinks). You will have to disassemble the thingNote.
Take pictures of the cables and screws so you can reassemble it later. Remove the nuts and cables and test the resistance of the element (now
disconnected from the circuit) with the meter. You may have done that but I can't see it in the picture. If it is still about 100 ohms, the heating
element is ok.
Remove the zip ties either by cutting them or by unlocking them with a penknife. Disconnect the cables (see picture) and inspect them, as there may be
some crud in the contacts somewhere. Remove the screws and flip the board. See if there is anything linking the soldered ends of the contacts in the
circuit board. Use a paint brush (camel's hair, if possible; unused would be perfect) to sweep the dust or whatever that may be there.
Since you're using the paint brush, sweep all the inside of the mantle before putting everything back in place. If possible, substitute the screws.
Test the mantle with a new fuse.
If nothing works, take it to a TV repairman (if you can find any) to see what's wrong.
Note: and follow my somewhat idiotic procedure. I'm a veteran involuntary cheapskate (which means I'm
broke).
[Edited on 23-5-2024 by bnull]
Quod scripsi, scripsi.
B. N. Ull
P.S.: Did you know that we have a Library?
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LookingForAnswers
Harmless
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i checked the heatsink yesterday when i opened top. resistance is the same as on the picture. in fact i didnt check the board and rest stuff that you
showed me on the photo. I will do all you described above and post a result
Chemistry Pope
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Rainwater
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Assuming that you are measuring the resistance of the heating element in that photograph
Ohms law states V²/P = R
220²/500 = 96.8ohms
E²/R = P
So 220²/110.1 = 439.6Watts
This leave 60 watts left over for the motor (magnetic stirring)
Its not the heating element.
Unplug the unit from the wall.
Turn every nob to max, and every switch ON.
1) Measure the resistance of the fuse, it should be ~0, if it is not zero continue
2)Short out the blown fuse
3)Ohm out between wires that plug into the wall.
Record the results
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4) provide a better image of the transformer lable.
5) turn every nob to its lowest setting and every switch off.
6) remove the short placed on the fuse.
These 6 steps will help determine what type of fault you're dealing with.
Next will be testing the transformer. It could be as simple as the fuse broke during transport. Happens a lot
"You can't do that" - challenge accepted
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Mateo_swe
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If you have measured the heating element with one lead disconnected and got around 100ohms then your heating element is probably ok.
Then i would measure AC voltage out from the transformer to see that you got whatever AC voltage the transformer gives.
If you have any AC voltage its probably OK so far.
Next thing i would do is disconnect AC plug, remove the small PCB with the heatsink.
Cleant this with IPA and check if there is any sign of fault visually.
Especially check capacitor solder points and see if capacitor is loose. They often get bad connections and if you wiggle them you can see the pin has
got loose from the solder. If so resolder the pins.
See if there is a fuse on this PCB and measure if there is 0 or very low ohm over this one.
The 4 black diodes are a diode bridge, after these you should have a DC voltage, mesure this and see if you have something reasonable.
If the mantle used to work there is a good chance it will work if you clean everything with IPA like PCBs and contacts.
Also check fuses.
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bnull
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@Rainwater: 500 W is the heating power, as described in the label (image 4). The resistance of the mantle (and most of the heating elements used in
appliances) varies around 10% of the calculated (and rounded to the next decade) value. The manufacturers know that no one will verify the real power
output and complain. As @LookingForAnswers wrote, "when I turn on the heating, the fuses blow." The heating part is messed up. Which doesn't mean that
the tests you proposed should be skipped.
I took another look at the picture of the innards of the mantle. Here's what I've found:
A is obviously the control board. It has either a microcontroller or an op-amp based circuit. I think it is a
microcontroller because it is cheaper that way and it doesn't need much power.
B is a generic Chinese step-down transformer, from 220 V to 12 V, 0.6 A output. It supplies 12 V AC to the board. There will be
next to zero information about it. I've been through that before.
C shows a "MOT+" marking, so we can conclude that the stirring is done by a DC motor. In the rectangle, we can see four diodes,
which must necessarily be part of a rectifying bridge. The 12 V AC from the transformer is rectified to about 15.6 V DC. F is a
polarised capacitor, part of the ripple filter for the motor voltage. If we account for a voltage drop in the motor driver circuitry, we can suppose
that the motor D is a 12 V DC motor.
E is a dimmer. A low voltage signal from the microcontroller operates the triacs G. I assume they are triacs
because a low DC voltage controlling the higher AC voltage of the heating element is the simplest and cheapest solution.
[Edited on 24-5-2024 by bnull]
Quod scripsi, scripsi.
B. N. Ull
P.S.: Did you know that we have a Library?
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