Fixing a laboratory waterbath

[R_J]

Re: Fixing a laboratory waterbath

I was also thinking about this and I suspect it is a pulse transformer and not a relay. Likely similar to a Schurter IL series
What is your plan for the transformer with the leads ripped out?

[eccerr0r]

Re: Fixing a laboratory waterbath

Aha... yeah that looks like transformer, that bottom side shows a lot. It's probably is fine, all the better - finding a replacement of this one would be tough. If your triac doesn't appear shorted it may still be fine, else you may need to replace it again.

[vrasp]

Re: Fixing a laboratory waterbath

What about the triac? Can I assume that since the trace next to the "relay" (or let's call the the black thing) blew, the triac didn't suffer any damage. Do you think I should replace it?

Both sides of the black thing have continuity (between pins of the same side) in both directions. A fridge magnet sticks to both sides shown on the pictures but not the other 2 sides.

The writing says:

1/0,66
01/L06

I m trying to think what other info I could provide. If the signal that comes from the green/blue PCB is a DC signal then maybe we can rule out a transformer since they work with AC only.

[eccerr0r]

Re: Fixing a laboratory waterbath

That trace blew because you didn't put the insulator on. You need both the kapton/mica/... insulator with heatsink compound, plus the plastic shoulder washer. If the old screw doesn't fit with the shoulder washer, you need to find a thinner screw, usually #4 or M2.5 screws are thin enough.
Since you blew that trace, yes you may have blew the (relay). You might be able to get away with an arbitrary 12V relay but I still think it's optical because relays are not fast enough.

Then again perhaps the original designer was an idiot and designed it this way... *facepalm*

BTW, the "input" side should be quite conductive if it's a relay, this would be a good test and shouldn't get damaged by the shorting TRIAC. If it were a true optoisolator it needs to be an LED input, and these would be conductive in only one direction... again if it really is a relay, this is a very poor design.

Oh and another thought... it could be a transformer. Now discerning a damaged transformer and a relay with simple tools...

[vrasp]

Re: Fixing a laboratory waterbath

Oh man. I had no idea I needed an insulator (The previous triac had what looks like an insulator already on it). Maybe that explains the short. The triac did come with a sticky plastic part which must be it. I guess I might have to replace it again.

Everything was working fine with the transformer set up that way. The 5v from the 7805 do go to the LED.

The relay is somewhat heavy. I ll try the magnet test. I thought it was bad because the high current side is always closed and so has continuity. Also the trace that blew was where the relay was (you can see on the photo I put some copper wire with solder on it).

(Please dont give up haha)

[eccerr0r]

Re: Fixing a laboratory waterbath

oh gawd now I see that the two boards go together component side to component side, I thought they were stacked... this makes a huge difference, and previous assumptions made earlier on may need to be invalidated... ugh...

1. How did you get away without an insulator on the TRIAC? Was this repaired before you worked on it? If so I'm very sorry. If you did replace it, you missed an insulator.
2. It looks like the 5V from the transformer board is actually the LED power supply after all, and the transformer may be connected wrong.
3. What gave you the impression the relay or whatever it is ... is bad? Also relays are denser than optoisolators, does it actually feel dense? Does a magnet stick to it?

Sigh. I hate remote debug. About ready to give up on this.

[vrasp]

Re: Fixing a laboratory waterbath

Here are some more pictures and a video. Hopefully, that helps.

The red capacitor and the "relay", or whatever it is, have been removed.

https://vimeo.com/575955271

The burned trace next to the triac is from the previous triac. This one is new. There are some cables hanging that I used to make it easier to measure pins I couldn't get to. These will be removed once I put everything back together.

[R_J]

Re: Fixing a laboratory waterbath

Now that I see the under side of the board, that to220 is likely a +5volt regulator ic and not the relay driver. The relay is driven by the heater control board so that would need to be traced to determine the relay coil voltage.

[vrasp]

Re: Fixing a laboratory waterbath

The reasons why I'm doubting relay:

- Voltage of the relays are typically printed on the relay
- Switch characteristics are typically printed on the relay
- It appears to be controlling the triac if that really is a triac there - versus a load. Again I don't see the connections so have to make assumptions with the incomplete data here.
- tracing the input path, what a mess, the device is being driven with very little current, not enough for a relay due to a resistor in series with the current path.

My current guess: "optoisolator" in quotes as a guess someone potted a LED and some optical sensors in that plastic.

But this is still just a guess. But if that device feels like it has metal in it then fine it can be a relay and will need to retrace the circuit more carefully. Really would like a picture with all the boards assembled together to make sure things are the way I thought they are connected.

It is really messy. It doesn't help that I replaced a bunch of stuff and sometimes on the other side of the boards to make it work with the space I have. I ve also blown a few things because of things touching the grounded case again due to lack of space. But these things were replaced and it has worked fine since. Until this recent issue.

I ll try to tske some more pictures with more details.

The triac is a NTE56010.

[vrasp]

Re: Fixing a laboratory waterbath

You need to post a clear (in focus) high res, picture of the trace side of the board the relay is mounted on.
Looking at the top suggests the small bridge rectifier and the 470µf capacitor are the supply for the relay, the to220 transistor controls the relay coil, The small glass diode next to the relay will be across the relay coil. I suspect the relay coil is either 12 or 24v based on the voltages marked on the transformer

This is a picture with diagram from the very beginning of this "journey". Someone from reddit made this for me. I think it s useful in this case. You can see the connections where the relay is, if it really is one. I think it is though, but that's my non professional opinion.

It would make sense that it is. The lower current side is connected to the pins (here labelled heater control signal) that go to the control PCB (not seen here) and activates the high current side which is connected to the gate. When the relay closes the circuit, the gate recieves a current and the triac conducts current to the heating element. Again, thats my non professional understanding of this circuit.

Edit: there is a component (looks like a zener but I ll have to check) that is not seen on this picture. It s above the red capacitor and in front of the relay. It connects the relay to the gate of the triac. Sorry if this is confusing. I m gonna take better pictures and get back to you.

[eccerr0r]

Re: Fixing a laboratory waterbath

The reasons why I'm doubting relay:

- Voltage of the relays are typically printed on the relay
- Switch characteristics are typically printed on the relay
- It appears to be controlling the triac if that really is a triac there - versus a load. Again I don't see the connections so have to make assumptions with the incomplete data here.
- tracing the input path, what a mess, the device is being driven with very little current, not enough for a relay due to a resistor in series with the current path.

My current guess: "optoisolator" in quotes as a guess someone potted a LED and some optical sensors in that plastic.

But this is still just a guess. But if that device feels like it has metal in it then fine it can be a relay and will need to retrace the circuit more carefully. Really would like a picture with all the boards assembled together to make sure things are the way I thought they are connected.

[R_J]

Re: Fixing a laboratory waterbath

You need to post a clear (in focus) high res, picture of the trace side of the board the relay is mounted on.
Looking at the top suggests the small bridge rectifier and the 470µf capacitor are the supply for the relay, the to220 transistor controls the relay coil, The small glass diode next to the relay will be across the relay coil. I suspect the relay coil is either 12 or 24v based on the voltages marked on the transformer

[vrasp]

Re: Fixing a laboratory waterbath

Show a picture of the bottom of this device
I am not sure what this device is it could be several things

Why are you assuming it's a relay? What evidence do you have?

I'm beginning to think it's not even a relay ... and have no clue what it is...

I was told it s a relay. It has 4 pins on the bottom. I ll post a picture.

[vrasp]

Re: Fixing a laboratory waterbath

The trace that goes from the 120VAC to the capacitor and relay was shorted and blew up. I m not 100% sure it's the relay, but the short happened where the relay was. Maybe it s the red capacitor next to it, or both. Without being 100% sure I was going to replace both the capacitor and relay. I have the specs for the capacitor but not for the relay.

Also I dont know if this is normal but the relay has continuity on the common end (high current end). The circuit inside the relay, where the triac would be connected, is always closed even without current (it tested it off the PCB). I put it on a breadboard and connected 6v to the low current circuit to see if I can close or open the high current circuit at will but it doesnt change anything. I dont know if this is how a relay is tested.

[sam_sam_sam]

Re: Fixing a laboratory waterbath

Show a picture of the bottom of this device
I am not sure what this device is it could be several things

[eccerr0r]

Re: Fixing a laboratory waterbath

Why are you assuming it's a relay? What evidence do you have?

I'm beginning to think it's not even a relay ... and have no clue what it is...

[vrasp]

Re: Fixing a laboratory waterbath

Or if you cant figure out the specs from the info I provided. What tests can I run to get that information. Should I measure the incoming activating voltage? Or is it the current that matters in this case?

[vrasp]

Re: Fixing a laboratory waterbath

For the relay unless there is a part number on the relay it is going to very difficult to know what will fit on the board or use some type of relay that you can find the relay socket and wire them to the board

The relay is 24 x21 mm. I think as long as I know what specs I need then I ll try to find something that fits. The part I have trouble with is all the relay specs I dont understand. For example, it s getting 120VAC. Should the relay therefore be rated at 240v minimum? The 120VAC side is connected to the 800v 16A triac. Should the relay be rated at 16A or higher as well? I think both answers to these questions are yes, it should. However I know electronics can be more complicated than that. Same with the coil voltage and other specs. How do I know what to get?

Thank you!

[sam_sam_sam]

Re: Fixing a laboratory waterbath

For the relay unless there is a part number on the relay it is going to very difficult to know what will fit on the board or use some type of relay that you can find the relay socket and wire them to the board

[sam_sam_sam]

Re: Fixing a laboratory waterbath

Ok if the pads are ripping off the board then you are putting to much force on the connector wiring which should be avoided if possible even if this means you have to extend the wiring somewhat or solder the connectors when everything is mounted

Or you are not getting the wire connector hot enough like I said earlier heat the connector and touch the solder to the wire connector not on the iron tip or you need to use flux on the wire connector if the solder is not staying on the connector