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-   -   Fixing a laboratory waterbath (https://www.badcaps.net/forum/showthread.php?t=96459)

vrasp 07-23-2021 06:32 PM

Re: Fixing a laboratory waterbath
 
Quote:

Originally Posted by sam_sam_sam (Post 1060489)
Okay your voltages are are not what the data sheet says it should be so you have some real issues with this

Could it be that these voltages are for when the TRIAC is in circuit?

I bought a new TRIAC, 15A fuses to place before MT1 and 0.1A fuses to place before the Gate. I hope to be able to troubleshoot the issue without having to replace the TRIAC again. Also maybe seeing which fuse blows will help me determine whether the issue is at the Gate of the TRIAC or at MT1 and MT2.

Quote:

Originally Posted by R_J (Post 1060494)
The triac is pulse controlled. There are control pulses on the primary side (from the control board) the triac has the gate and one MT connected to the secondary of the transformer. With no pulses from the transformer, the gate is effectively turned off, when there are pulses present the triac turns on.
The pulses are likely to control the temperature of the element and provide zero cross switching to prevent noise on the ac line.
The triac connection which is connected to the transformer should likely be connected to neutral, and the element should connect between line (120vac) and the other triac connection.

Nice explanation. Thank you!

The line with MT1 has a capacitor connected to neutral. I don't know if that counts as being connected to neutral. The heating element is connected to MT2 and MT1 is connected to 120v. MT2 and MT1 are connected within the TRIAC (when activated) but not on the PCB. I hope that makes sense.

Unless the short messed up with the control PCB via the transformer (if that's possible), everything on this circuit should work. It's only made up of the TRIAC, 2 zener(I m still not sure those are zeners but they look like it), the heating element, and a capacitor which is new. The heating element has a resistance to neutral that is within range of what I read it should be (around 10-15 Ohms I think).

R_J 07-23-2021 06:52 PM

Re: Fixing a laboratory waterbath
 
2 Attachment(s)
Based on what you said, this seems to be the configuration. You say 2 zener? are there 2 zeners? or only the one?
It is possible it is not a zener but a diac

vrasp 07-23-2021 06:54 PM

Re: Fixing a laboratory waterbath
 
1 Attachment(s)
Quote:

Originally Posted by R_J (Post 1060503)
Based on what you said, this seems to be the configuration. You say 2 zener? are there 2 zeners? or only the one?
It is possible it is not a zener but a diac

Yes I think that's exactly it!

This is what there is between the transformer pin and Gate. It looks like it's touching that terminal in the photo but its not. It connects to the gate on the other side. There is another one between the two primary pins too ( so where you wrote "to trigger circuit").

vrasp 07-23-2021 08:46 PM

Re: Fixing a laboratory waterbath
 
That other one might actually be a zener. There is 0.5v across.

R_J 07-23-2021 09:23 PM

Re: Fixing a laboratory waterbath
 
That is just a 1N4148 small signal diode, neither a zener or a diac

sam_sam_sam 07-24-2021 08:49 AM

Re: Fixing a laboratory waterbath
 
What would the signal transformer purpose be in this circuit
Is this a way to isolate the triac from the rest of the circuit
Or am I under the wrong assumption of what it’s purpose is for

R_J
Quote

“The triac is pulse controlled. There are control pulses on the primary side (from the control board) the triac has the gate and one MT connected to the secondary of the transformer. With no pulses from the transformer, the gate is effectively turned off, when there are pulses present the triac turns on.
The pulses are likely to control the temperature of the element and provide zero cross switching to prevent noise on the ac line.”

I did not see this until just now

How common is it to use a signal transformer with a triac setup

Can you push more current with it pluse-ing the signal is stead of just using a turn on signal to the triac

eccerr0r 07-24-2021 09:18 AM

Re: Fixing a laboratory waterbath
 
Definitely not DIAC, DIACs do not have bands on them.
Yes that transformer is there solely for isolation. The whole design probably could be made one heck of a lot simpler with a MOC3041 but probably designed with NIHism...

sam_sam_sam 07-24-2021 02:43 PM

Re: Fixing a laboratory waterbath
 
Eccerror

Was this the word you trying to spell

“nihilism”

Just curious

eccerr0r 07-24-2021 04:27 PM

Re: Fixing a laboratory waterbath
 
Nope
N-I-H-ism if I have to spell it out.

vrasp 07-24-2021 05:42 PM

Re: Fixing a laboratory waterbath
 
Should the potential between GATE and MT1 be the same? There is no information of that in the datasheet. Right now it's 1.1v. Maybe due to the 1N4148.

This is my plan:
1. Solder the new 800v 15A TRIAC.
2. Solder a 15A fuse on MT1 and a 0.1A fuse on GATE.
3. Plug the waterbath in series with one or a few 100w bulbs.
4. Measure the voltages between GATE and MT2 and MT1. It might allow to understand where the issue is coming from.

Something I noticed when I had 300w of bulbs to limit the current (before I blew it) - the TRIAC and heatsink never even got warm. At the time I thought it was due to the current being limited, but now I m thinking maybe the TRIAC was not working at all.

I dont know where the issue might be coming from. The circuit is basically just a current activating a TRIAC and closing a high current circuit to the heating element. Not sure what is causing the TRIAC to blow. I ve been ignoring the input side of the transformer. It is connected to the control board. Could a wrong voltage/current on the input cause a current high enough on the ouput to blow the TRIAC?

I d love to hear some suggestions on how to get to the bottom of this.

Thank you!

petehall347 07-24-2021 07:05 PM

Re: Fixing a laboratory waterbath
 
i suppose you could replace the heating element with a bulb .

eccerr0r 07-24-2021 07:25 PM

Re: Fixing a laboratory waterbath
 
^ this

and again how do you know it blew or not, it would need to get hot to blow. It was rated for 15A after all, which would be in the range of tripping upstream fuses, wires, etc.

The key thing is that when it's out of circuit, MT1 and MT2 should not conduct in either direction when gate is disconnected. Now some conductivity between G ant MT1 is expected as there's a diode region there.

Then the other thing is if you're connecting the gate to the wrong terminal. Hooking gate between what would be MT1 and MT2 would instantly fry it...

sam_sam_sam 07-24-2021 07:47 PM

Re: Fixing a laboratory waterbath
 
When I troubleshoot my battery spot welders that uses a triac ( that uses a high current transformer) and want to test the controller function I will use an incandescent light bulb so I do not trip the breaker because some of these controllers have issues with the programming

These battery spot welder machines controller are suppose to control the current going to the transformer but when the controller has issues it will one of two things one turn the transformer fully ON and fry the triac and trip the breaker to the hole house or does not power the transformer at all

I have a feeling that your controller is one that is suppose to control the current as well and if this is the case it might not be doing this and just turning it fully ON which might be a problem

My suggestion would be try programming the controller with an incandescent light bulbs so you can see if the controller is working correctly and you can heat up the sensor to pretend that it has reached the set point then let it cool down and do this several times this would allow you to see if the triac is functioning correctly or not

And when you test it with the heater element you really need to have an amp probe on the heater element to make sure that you are over current-ing the triac you should be unless you have an issue with the controller

eccerr0r 07-24-2021 10:06 PM

Re: Fixing a laboratory waterbath
 
And that's why I'd suspect that the TRIAC should be fine as is controlling a shorted heating element, even... and it should end up throwing a breaker before it "instantly fries the TRIAC". With the past history of this thread, I'd highly consider the possibility of the miswiring of the TRIAC when soldering it, causing it to blow. Again connecting the gate terminal and MT1 (the diode drop) across mains voltage will instantly fry the TRIAC. Other miswirings would just cause issues in it turning on or it being always turned on.

Seems as typical for all these three terminal devices that aren't high powered RF devices, when facing the TO-220/TO-247 the left pin is the high impedance input (gate for TRIAC, base for BJT, gate for MOSFET), center pin (and thus metal tab) is the "output" (MT2 for TRIAC, collector for BJT, drain for MOSFET) and the right pin the low impedance common input (MT1 for TRIAC, emitter for BJT, source for MOSFET).

Oddly enough SCRs seems to not follow this pattern - more like diodes ... and again RF transistors where the center pin is typically emitter/source...

vrasp 07-24-2021 11:12 PM

Re: Fixing a laboratory waterbath
 
Quote:

Originally Posted by petehall347 (Post 1060631)
i suppose you could replace the heating element with a bulb .

I ll do that too!

Quote:

Originally Posted by eccerr0r (Post 1060632)
^ this

and again how do you know it blew or not, it would need to get hot to blow. It was rated for 15A after all, which would be in the range of tripping upstream fuses, wires, etc.

The key thing is that when it's out of circuit, MT1 and MT2 should not conduct in either direction when gate is disconnected. Now some conductivity between G ant MT1 is expected as there's a diode region there.

Then the other thing is if you're connecting the gate to the wrong terminal. Hooking gate between what would be MT1 and MT2 would instantly fry it...

It blew when I went from plugging with the bulbs to without them, thinking it was working fine. The bulbs were bright but I thought this to be normal as there is up to 15A pulled to the heating element. When I say I blew it I mean it actually went :poof: and is physically damaged. I m pretty sure they re soldered to the right terminals but I ll double check. One thing I can think of is that I dont know the exact size of the screw I used to mount it. It was definitely quite smaller than the TRIAC hole and fit the washer. There was also no continuity with the screw or heatsink. This time I m gonna get an M4 just to make sure.

There is no upstream fuse. Just the lab circuit breaker.

Quote:

Originally Posted by sam_sam_sam (Post 1060635)
When I troubleshoot my battery spot welders that uses a triac ( that uses a high current transformer) and want to test the controller function I will use an incandescent light bulb so I do not trip the breaker because some of these controllers have issues with the programming

These battery spot welder machines controller are suppose to control the current going to the transformer but when the controller has issues it will one of two things one turn the transformer fully ON and fry the triac and trip the breaker to the hole house or does not power the transformer at all

I have a feeling that your controller is one that is suppose to control the current as well and if this is the case it might not be doing this and just turning it fully ON which might be a problem

My suggestion would be try programming the controller with an incandescent light bulbs so you can see if the controller is working correctly and you can heat up the sensor to pretend that it has reached the set point then let it cool down and do this several times this would allow you to see if the triac is functioning correctly or not

And when you test it with the heater element you really need to have an amp probe on the heater element to make sure that you are over current-ing the triac you should be unless you have an issue with the controller

I dont know if there is a controller but there might be. Is it a chip? How do I find it?

I might have to get a better multimeter or an amp probe. Mine only goes up to 10A.

Thanks guys!

eccerr0r 07-25-2021 01:19 AM

Re: Fixing a laboratory waterbath
 
Did it blow when the heater wasn't supposed to be on, or was the heater supposed to be on at that point?

This is specifically to trigger the heater right? How is the chiller supposed to be turned on?

petehall347 07-25-2021 03:33 AM

Re: Fixing a laboratory waterbath
 
https://i.ebayimg.com/images/g/PRUAA...aH~/s-l400.jpgyour triac should have one of these in the hole ...

eccerr0r 07-25-2021 07:23 AM

Re: Fixing a laboratory waterbath
 
I think he does, https://www.badcaps.net/forum/attach...4&d=1626717671 but M4 is too big (should be M3 or #4), and the plastic shoulder washers for #6 screws seems rare.

Again something really wrong is here that's not being described. In the off state, according to the PCB, gate is shunted to MT1 through the diode/isolation transformer and therefore should be off. Unless MT2 reaches above the isolation voltage limit it won't heat up until it's forced to turn on. So therefore unless there's a wiring mistake somewhere, this makes no sense and not worth investigating further. Based on history, wiring mistakes are abound and has been extremely annoying to work through.

vrasp 07-25-2021 07:23 AM

Re: Fixing a laboratory waterbath
 
Quote:

Originally Posted by eccerr0r (Post 1060656)
Did it blow when the heater wasn't supposed to be on, or was the heater supposed to be on at that point?

This is specifically to trigger the heater right? How is the chiller supposed to be turned on?

It blew when the heater was on. The heater turns on with the waterbath because the set temperature is above the water temperature. If I want to turn it off I have to set the temperature to below the water temp.

The chiller is turned on with another switch. There is no PCB for that. The switch just closes the circuit to the compressor and it stays on as long as the switch is activated. So one could turn on the heating and cooling at the same time if they wanted to.


Quote:

Originally Posted by petehall347 (Post 1060679)
https://i.ebayimg.com/images/g/PRUAA...aH~/s-l400.jpgyour triac should have one of these in the hole ...

Yes I have those. They're supplied with the TRIAC. It s the screw I m unsure of. Although I think it was small enough.

sam_sam_sam 07-25-2021 07:49 AM

Re: Fixing a laboratory waterbath
 
“ I dont know if there is a controller but there might be. Is it a chip? How do I find it?”
You just have to Google the part numbers to find what each part number


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