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draculic acid69
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Heating mantle blew up WTF!!!!!
Ok a year ago I bought a heating mantle/stirrer as soon as I bought it I plugged it in turned it up to max and let it burn off the coating, put a
flak of water in it and boiled it for an hour let it cool down,played with the stirrer then put it back in the box.no problems.box then sits in back
of cupboard until I pulled it out and setup everything to give it its first trial run today. Then as I go to put the cord from the power pack into the
mantle and it makes contact with the pins BOOM!!! the fucking thing shoots out a massive spark followed by smoke.something inside either shorted or
malfunctioned and after opening it up it looks like the transformer has shorted against the leads and the cover but why now and how? No metal was
touching any other metal no wires were exposed or split . just black burn marks on part of the transformer. I don't get this.has anyone ever had one
short out like this?
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XeonTheMGPony
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A ton of things will cause this, any thing from china, open it up and check all the electricals, that is oft the weak point of made in China is sloppy
assembly, lose connections, poor ones.
Odds are, the brains will still be good, so replace Xformer, do the above and it aut to come back to life.
Heating it dry = very bad bty
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Sulaiman
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Quote: Originally posted by XeonTheMGPony  | | ...any thing from china, open it up and check all the electricals, that is oft the weak point of made in China is sloppy assembly, lose connections,
poor ones... |
VERY good advice.
CAUTION : Hobby Chemist, not Professional or even Amateur
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draculic acid69
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It was the 2nd time I've ever plugged it in. Nothing wrong with it when I put it back in the box.then I plug it in and its fucked.dont get it.
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Ubya
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| Quote: Originally posted by draculic acid69 | | It was the 2nd time I've ever plugged it in. Nothing wrong with it when I put it back in the box.then I plug it in and its fucked.dont get it.
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maybe the leads were 1mm from touching at the beginning and once stored for a long time they touched (insulation contracting/expanding?), you never
know sith this things, it could work 100 times and blew up the 101
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feel free to correct my grammar, or any mistakes i make
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Herr Haber
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Hehe, the one I got from China never worked.
I stored it planning on doing exactly what was suggested above but maybe it'll work when I plug it in !
The spirit of adventure was upon me. Having nitric acid and copper, I had only to learn what the words 'act upon' meant. - Ira Remsen
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draculic acid69
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It looks like an insulated wire touched between the cover and top of the xformer but how would that cause a short bcoz the cover wasn't touching? Also
looks like the 2 secondary wires coming out of the xformer have burned and melted slightly.i dont know if it fried anything else. Who's the best ppl
to get to fix this stuff? Do I need to find an electrical engineer? Is there a company that fixes this type of stuff?
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Sulaiman
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Repairs cost components (cheap) and labour time (not cheap)
If you are not in a hurry, and have a multimeter, I presently have the time to help remotely.
If you do not have a multimeter I can recommend the cheap Aneng AN8002 as I've used and tested it a lot.
(I've used it many many times with domestic 240 Vac but I've not used (do not trust) it on 415 Vac even though it is 'rated' for it - high power arc
flash in your hand is not funny. Multimeter fuses for high energy systems are expensive but necessary)
CAUTION : Hobby Chemist, not Professional or even Amateur
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draculic acid69
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While I trust my soldering and low risk DC electrical skills I don't trust my safety on doing AC work.i just don't understand it enough and one fuckup
can lead to death.thanks for the offer sulaiman but I'll have to think about it.
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Sulaiman
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I understand your concerns, 240 Vac can be fatal,
but I'm a lucky optimist ... I've felt 240 Vac more than once - PAIN !
Electrocution by 240 Vac is quite unlikely, but if in doubt ... do not mess with 240 Vac.
Comparing with hobby chemistry, I'd put the risk at equivalent to chlorine gas generation.
CAUTION : Hobby Chemist, not Professional or even Amateur
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wg48temp9
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| Quote: Originally posted by draculic acid69 | | While I trust my soldering and low risk DC electrical skills I don't trust my safety on doing AC work.i just don't understand it enough and one fuckup
can lead to death.thanks for the offer sulaiman but I'll have to think about it. |
I good/minimum design rule is insure that a minimum of two failures/fuckups are required to kill or seriously injury you. For example the metal
enclosure of 240Vac electrical equipment should be earthed and internal wiring should be insulated so it would require failure of the insulation and
failure of the enclosure earth before the enclosure becomes live and potentially lethal.
An other example is when boiling a liter of drain cleaning fluid ensure that the boiler is sitting in a container that will capture all drain cleaner
in the event that the boiler fails and releases the boiling drain cleaner. Of cause this is only applicable if the probability of a single failure is
low as the probability of two simultaneous low probability failures occurring together is very low.
.
I am wg48 but not on my usual pc hence the temp handle.
Thank goodness for Fleming and the fungi.
Old codger' lives matters, wear a mask and help save them.
Be aware of demagoguery, keep your frontal lobes fully engaged.
I don't know who invented mRNA vaccines but they should get a fancy medal and I hope they made a shed load of money from it.
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Herr Haber
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| Quote: Originally posted by wg48temp9 | Of cause this is only applicable if the probability of a single failure is low as the probability of two simultaneous low probability failures
occurring together is very low.
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Unless you are just about to replace a failed HDD from a Raid array.
Feeling good an cozy and then...  second one fails !
I might take you up on your offer Sulaiman 
The spirit of adventure was upon me. Having nitric acid and copper, I had only to learn what the words 'act upon' meant. - Ira Remsen
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XeonTheMGPony
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| Quote: Originally posted by draculic acid69 | | While I trust my soldering and low risk DC electrical skills I don't trust my safety on doing AC work.i just don't understand it enough and one fuckup
can lead to death.thanks for the offer sulaiman but I'll have to think about it. |
AC work is same as dc for all intents and purposes of this repair, Volts must match, the current rating of new Xformer can be larger but never lower
ensure all connections are clean tight and well insulated you will have no issues
Sounds like the failure point was an internally shorted transformer where it arced out the top.
A couple pictures will help. as it could be an RF choke too, with out seeing it to much guess work for my liking.
[Edited on 21-7-2019 by XeonTheMGPony]
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Sulaiman
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| Quote: Originally posted by Herr Haber | Unless you are just about to replace a failed HDD from a Raid array.
Feeling good an cozy and then... second one fails !
I might take you up on your offer Sulaiman |
Long ago I ignored a mainframe memory IC failure
not a problem, as the chance of a second memory IC in the same word failing before the next scheduled maintenance were negligible...I assumed.
At the moment I'm free so, you have a multimeter ?
(I should remember or search but I'm lazy)
CAUTION : Hobby Chemist, not Professional or even Amateur
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Dr.Bob
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"as soon as I bought it I plugged it in turned it up to max and let it burn off the coating"
This is the problem, you burned it to a crisp. They are not made to heat dry and to a maximum unless being cooled by a load. They are designed to
be controlled and heated slowly while a flask full of material is in them. Doing what you did is the worst thing possible for a heating mantle.
They are not like self cleaning ovens, they are made of fabric that will melt and char if heated too much. I get them from people all of the time
like that. I have been using the same heating mantles for 10-30 years and they don't ever fail, so I am pretty sure that I am doing it right, plus I
was actually taught the proper use of them. Don't ever heat them above about 50% of their rated power until you have tried lower power and it did
not overheat, you should only need to heat above 50% when using water or other high boiling solvents. For most organics, they rarely are above
30-50%.
What you did was like testing a new car by holding the gas pedal down with a brick until the engine blows. For many things, you don;t need to go to
11...
[Edited on 21-7-2019 by Dr.Bob]
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XeonTheMGPony
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| Quote: Originally posted by Dr.Bob | "as soon as I bought it I plugged it in turned it up to max and let it burn off the coating"
This is the problem, you burned it to a crisp. They are not made to heat dry and to a maximum unless being cooled by a load. They are designed to
be controlled and heated slowly while a flask full of material is in them. Doing what you did is the worst thing possible for a heating mantle.
They are not like self cleaning ovens, they are made of fabric that will melt and char if heated too much. I get them from people all of the time
like that. I have been using the same heating mantles for 10-30 years and they don't ever fail, so I am pretty sure that I am doing it right, plus I
was actually taught the proper use of them. Don't ever heat them above about 50% of their rated power until you have tried lower power and it did
not overheat, you should only need to heat above 50% when using water or other high boiling solvents. For most organics, they rarely are above
30-50%.
What you did was like testing a new car by holding the gas pedal down with a brick until the engine blows. For many things, you don;t need to go to
11...
[Edited on 21-7-2019 by Dr.Bob] |
This^
I break mine in by putting a flask of water in them, start off low power and hold the water at 50 for 30m to an hour, then to boiling for 30m, during
this I check for ground leakage and any weird hot spots.
Then I use it. My mantle has don several sulfuric acid distillations and a crap load of much cooler distillations and still going strong.
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draculic acid69
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The instructions say to burn off the coating with nothing in it first.then I boiled a flask of water in it this was actually done a few days
apart.nothing wrong at this point.
Just took the board off mantle and its cooked.the copper tracks have come off the board.it looks like the power has surged thru from the plug thru the
board and then out into the xformer where it arced and smoked.
The black at the base of red wires is where it must have arced out and melted.
The spot on the cover is where the spark hit the metal plate. that was right over the top of the transformer. On the board where you can see the shiny
copper tracks is where they have come off the board.they are the tracks between the red xformer wires and the mains input.
   
[Edited on 22-7-2019 by draculic acid69]
[Edited on 22-7-2019 by draculic acid69]
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draculic acid69
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Now that the board is fukt I can either replace the transformer with a new one and resolder a new board bcoz I'm sure I can't buy one or I can just
plug a Variac directly into the nichrome element.or I can use my other mantle only problem there is no stirrer and it's all in Chinese.
[Edited on 22-7-2019 by draculic acid69]
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highpower48
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Best just to get a Variac and be done with it. This will also a allow you to buy cheap mantel heating liners and make your own. And a Variac will give
you a lot more control of the temperature. ..
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markx
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How much "furniture" is on the other side of the control board? It does not look too complicated....perhaps there is still hope for repairing it.
It sure seems that there was a serious short somewhere in the circuitry and most probably it was caused by a semiconductor device failing.
Is the stirrer motor asyncrhonous type (AC driven) or a dc motor? I trust most of the control board deals with the rpm control of the AC
motor....usually it is built that way.
To regulate the heating mantle a simple thyristor driven "dimmer" circuit can be used instead of a variac. They are dirt cheap, small, and can commute
a serious amount of power without oveheating.
Like this one e.g.:
https://www.ebay.com/itm/Electronic-2000W-Imported-Thyristor...
I use one to regulate the temperature of my soldering iron...works beautifully.
The stirrer motor control, if it happens to be AC is a bit trickier. But if you are lucky and it is a DC motor then a variety of PWM speed control
modules are available. These can be used to regulate the stirrer speed.
E.g.:
https://www.ebay.com/itm/PWM-DC-Motor-Speed-Control-Regulato...
In case of AC motor you basically need a VFD type solution....actually I saw a really small single phase module that could be used for the purpose,
but I can not find a reference right now.
Exact science is a figment of imagination.......
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XeonTheMGPony
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the three pin unit that the track leads to I suspect is a triac or scr, it may have shorted. lets get a pic on the top side, other wise a bit of
ruffled tracts are of no concern, just get some conformal coating and recoat, and if broken just solder wires in their place
now days you can get cheap dimmer style motor speed controles.
[Edited on 22-7-2019 by XeonTheMGPony]
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draculic acid69
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The motor is d.c. controlled. I talked to an electrical engineer and he said there should be a fuse attached somewhere.there isn't one.no rf choke on
there anywhere but is it even needed on a heating mantle?.they really make this shit cheap.
Are these thyristor things really a suitable thing to control a mantle? What's the difference between a Variac and a thyristor?
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Sulaiman
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| Quote: Originally posted by draculic acid69 | The motor is d.c. controlled. I talked to an electrical engineer and he said there should be a fuse attached somewhere.there isn't one.no rf choke on
there anywhere but is it even needed on a heating mantle?.they really make this shit cheap.
Are these thyristor things really a suitable thing to control a mantle? What's the difference between a Variac and a thyristor?
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Fuses and chokes cost the manufacturer money 
I doubt that a thyristor is used, possibly a pair but almost always a triac is used.
The main difference between a variac and a phase angle controller (dimmer) is cost.
A variac will eventually need a new carbon brush, and a dimmer will need a new potentiometer.
A variac will not need rfi supression, unlike a dimmer.
(dimmers work just fine without rfi supression, nearby radios or sensitive electronic equipment may pick up noise if the dimmer is not rfi supressed)
[Edited on 23-7-2019 by Sulaiman]
CAUTION : Hobby Chemist, not Professional or even Amateur
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draculic acid69
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The board doesn't look too complicated and apart from the lifted tracks the components or "furniture"as you refer to it dont look burned out or
damaged
there's an electrolytic capacitor and it isn't popped or leaking and that's usually the first sign there's something wrong with them.they don't have
burn marks anywhere.so maybe I can desolder and make a new board.its doable.might be quicker to learn Chinese and put a stirrer in my other one.
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markx
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| Quote: Originally posted by draculic acid69 | The motor is d.c. controlled. I talked to an electrical engineer and he said there should be a fuse attached somewhere.there isn't one.no rf choke on
there anywhere but is it even needed on a heating mantle?.they really make this shit cheap.
Are these thyristor things really a suitable thing to control a mantle? What's the difference between a Variac and a thyristor?
|
The thyristor/triac circuits are absolutely spot on for controlling passive loads like a heating element or incandecent light bulb....or a soldering
iron in my case. Just do not trust the wattage rating on these things to the maximum. Get at least a double size beefier unit (e.g if your mantle is
rated at 1kW then get at least a 2kW control module). They work by switching off part of the AC wave....how much is cut off depends on the position of
the control knob. Effectively this regulates the amount of energy that is fed into the heating element. A simple analogy would be to include a diode
in series with an AC heater circuit. The diode conducts only in one direction, cutting off the halfwave and thus also 50% of the energy:
http://www.pcbheaven.com/wikipages/Dimmer_Theory/
A variac is simply a tunable transformer that can vary the output voltage by turning the knob....thus, the lower the output voltage, the lower the
generated energy in the heating element. They tend to be bombproof, but are bulky....a triac/thyristor circuit is tiny and light. It can be hidden in
the original case of the equipment with ease and it shall accomplish the same effect. I do not think one can fit a variac into the original casing.
If your stirrer motor is DC type then you are in great luck....there is an endless selection of DC PWM type speed control boards available. Again they
are cheap, small and really functional.
So even if you are not able to repair the original board then you can take replacement modules for a couple of dollars and with a little bit of
soldering and common sense get your equipment back in full operational condition
Also it would be a good idea to include fuses if they are missing in original schematic. Chinese tend to be really cheap and I've seen circuits that
lack absolutely any safety measures....a shortcoming that can cost dearly. So take care of that aspect also once you already are in there
Exact science is a figment of imagination.......
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