Sciencemadness Discussion Board

IKA/Chemglass troubleshooting?

monolithic - 10-10-2020 at 15:55

I recently bought a "for parts" hot plate, an old Chemglass Digital Hot Plate Stirrer which is a rebrand of an IKA RET control visc safety control S1.

Heating initially works fine in modes B and C but cuts out after a few minutes and gives me an ER 23 which is:
Quote:
Fault in SAFE TEMP H (Hotplate) adjustable safety circuit. / Difference between the setpoint and the actual values of the adjustable safety circuit for the heating plate temperature monitoring. / Switch ON in operating mode A and set the SAFE TEMP P to another value. If this clears the fault then the unit is switched on again, you can return to using the previous value.


I cycled to mode A turned up SAFE TEMP H to 300 C. I don't have an external probe so I can't set SAFE TEMP P to 300 C. I cycle back to mode B and C and I get the same ER 23 which cuts out heating at maybe 100 C. I took it apart and looked at the circuit board but nothing is really labeled so I'm lost but at the same time nothing is visibly burnt out. The heating element has 4 wires: two power (20 ohms) and two temperature sensing (1.6 ohms at about 24 C, varying with temperature.) I'm not sure how to determine if these temp wires are in spec? Does this sound right and if so, what else could be giving me this ER 23 error -- a completely blown motherboard?

[Edited on 10-10-2020 by monolithic]

valeg96 - 11-10-2020 at 01:57

I've never laid hands on that specific model of hotplate, but I've messed with some IKA RCT basic ones. Try to check for a small plastic screw on the side of the hotplate, that could be used to set the safety temperature. If it's set too low, after a short time of heating the safety temp is reached and the power is cut . Otherwise it's a fucked up board, which is basically the only reason why modern flat IKA hotplates fail. I wouldn't spend a dime on such poorly designed (or intentionally flawed!) equipment.

monolithic - 11-10-2020 at 03:56

Quote: Originally posted by valeg96  
I've never laid hands on that specific model of hotplate, but I've messed with some IKA RCT basic ones. Try to check for a small plastic screw on the side of the hotplate, that could be used to set the safety temperature. If it's set too low, after a short time of heating the safety temp is reached and the power is cut . Otherwise it's a fucked up board, which is basically the only reason why modern flat IKA hotplates fail. I wouldn't spend a dime on such poorly designed (or intentionally flawed!) equipment.


This is the newer (but still old) model that sets the setpoint entirely in software, there is no longer a screw on the side. :(

Do you have any suggestions for a cheaper, used digital hot plate with temperature overrun protection? I'm happy with my old Corning PC351 but apparently most Corning models, Fischer, VWR, Cimarec, etc. can fail in such a way to cause runaway heating. (See attachment.)

Attachment: RunawayHotPlates-2017Aug.pdf (247kB)
This file has been downloaded 376 times

edit: I think the motherboard is junk, the temperature knob just stopped responding to all settings even in set temperature mode.

[Edited on 10-11-2020 by monolithic]

valeg96 - 11-10-2020 at 05:45

Stay away from anything digital and/or with nanoprinted PCBs, or in other words, from anything you can't troubleshoot or repair yourself should a component break (e.g. the thing you bought)

Stay away from anything too slim, as the PCBs are way too close to the heating element and they will fry after 5-6 years of use (e.g. IKA RCT Basic)

Stay away from clunky cheaper hotplates made of sheet metal, as they overheat tremendously (e.g. old VELP hotplates).

The three best and sturdiest I have are the Heidolph 2002, Heidolph 3001 and IKAMAG RCT. They are still functioning after 30+ years of use, and if something fails you can buy another one for spare parts or fix the board yourself if you know some electronics. Additionally, they work at 220 V and have way more powerful motors than slim electronic ones. Just keep in mind that anything second-hand shouldn't be cranked up too much or left unattended, unless well tested in advance.

monolithic - 11-10-2020 at 06:00

Thanks, that's kind of what I thought. I was amazed at how much bullshit they crammed onto the PCB for something as simple as a hot plate stirrer! I think the optimal solution will be an old model like you mentioned plus a self-made safety relay to guard against any potential runaway heating scenarios in an unattended (overnight) reaction.

valeg96 - 11-10-2020 at 06:10

Fyi, these are the PCBs of a Heidolph 2002 (late '80s). Compare these, that lasted 30+ years, with what you found inside of yours.

Also, I forgot. Old hotplates can work as stirrers if the element burns out. Digital ones see that the element is burned and won't start at all, so you can't even repurpose them.

16024253970396962117628601535993.jpg - 2.2MB

[Edited on 11-10-2020 by valeg96]

Dr.Bob - 11-10-2020 at 06:26

I have also had way more issues with "digital" hotplates than with simple ones with analog knobs. I had many IKA digital ones break in a 10 years span, but the Corning and similar analogs one I still have are 20-30 years old and still working find. The most common issue I have with them is that the stirring speed control does not work, either being only fast oir only slow (less common). That was almost always able to be fixed easily, but the IKA models all needed repairs that either required parts not available or that cost more than the item cost.

valeg96 - 11-10-2020 at 06:44

The hotplates I mentioned in the other thread were all bought in 2009-2011, and fried in 2019. Some still had the purchase documents and all the paperwork, and the silicone cover. They were all fried because of poor design, and IKA offered to provide me with replacement boards for 200€ each. Not even if hell freezes over.

The other hotplates I have are from the late '80s and were repaired just fine, on the other hand. Unless you're shitting money, stay away from anything digital.

monolithic - 11-10-2020 at 06:49

Quote: Originally posted by valeg96  
Fyi, these are the PCBs of a Heidolph 2002 (late '80s). Compare these, that lasted 30+ years, with what you found inside of yours.

Also, I forgot. Old hotplates can work as stirrers if the element burns out. Digital ones see that the element is burned and won't start at all, so you can't even repurpose them.



[Edited on 11-10-2020 by valeg96]


Now compare what I spent the past few hours dicking around on...

https://i.imgur.com/34bTymY.jpg

I found out why the temperature knob stopped working -- the traces snapped in half on the shitty paper ribbon connector. Surprised they would cheap out rather than use a higher quality plastic ribbon. Oh well, only paid $50 for this. Going to try to sell the heating element (tested the element with a variac + monitored resistance, works fine) and motor (worked fine on the motherboard) and hopefully recover my "investment."

valeg96 - 11-10-2020 at 06:54

Selling may be the best option, especially because you can never be sure if that's the only issue or the main issue. Many digital hotplates often show error after error, so if you manage to solve one, another shows up. If you get into older and more "hands-on" equipment consider keeping spares, I've started doing that and it's been helpful through the years.

OldNubbins - 11-10-2020 at 18:39

Every hotplate/stirrer is just a resistance heating element and usually a shaded pole motor, the same motor in your bathroom fart-fan. They use convoluted SMT controllers because they are dirt cheap to have made overseas and thrown together at final assembly. It's too expensive to pay someone to hand-build a more robust through-hole board.

All you need is a temperature probe, some way to read it and turn a relay on and off to control heat. Shaded pole motors are bulletproof and can be controlled by chopping the current with a triac/SCR or even a mechanical relay. They build them to look fancy, interface with data collection, and justify the outrageous price tag.

valeg96 - 11-10-2020 at 21:36

Quote: Originally posted by OldNubbins  
Every hotplate/stirrer is just a resistance heating element and usually a shaded pole motor, the same motor in your bathroom fart-fan. They use convoluted SMT controllers because they are dirt cheap to have made overseas and thrown together at final assembly. It's too expensive to pay someone to hand-build a more robust through-hole board.

All you need is a temperature probe, some way to read it and turn a relay on and off to control heat. Shaded pole motors are bulletproof and can be controlled by chopping the current with a triac/SCR or even a mechanical relay. They build them to look fancy, interface with data collection, and justify the outrageous price tag.


Thank you for translating my thoughts into something more technically savy. I don't know much of electronics, I've just messed around with them enough to realize how crap the modern ones are. I recommend those models also because their shaded pole motors are physically huge and powerful, and can't be stopped by your average magnet strolling by.