gyro_gearloose Posted January 7, 2016 Share Posted January 7, 2016 Hi we've got a Unique 2 hazer (not a 2.1, if that makes any difference) which I believe has a faulty temperature sensor. What happens is when it is powered up it will, after a few minutes, trigger the over temperature protection device. If you know anything about Unique hazers you'll know that this device does not self-reset, and it is a pain to reset manually as you have to open up the case every time it happens! When our hazer over heats there are no error messages on the display. This leads me to suspect the the temperature sensor soldered onto the copper tubing is at fault. The fan is not clogged, which is the usual cause of an overheating hazer, so the only other cause I can think of is the temperature sensor is faulty so the hazers CPU doesn't know when to cut the power to the heating element: hence it then over heats and triggers the awkwardly placed protection device. Does anyone know what sort of sensor it is, and can it be replaced by itself? I know I can buy a new heater block with everything attached, but this seems quite an expensive way of fixing my problem. Thanks Link to comment Share on other sites More sharing options...
alistermorton Posted January 7, 2016 Share Posted January 7, 2016 Don't know about the sensor, but could it also be that the control circuit has failed, so even though it has tried to cut power to the heater it is sill heating, hence it overheats? Isn't the heater controlled by a triac? Could that have failed short circuit? Link to comment Share on other sites More sharing options...
gyro_gearloose Posted January 7, 2016 Author Share Posted January 7, 2016 But wouldn't that still trigger an error message if the temperature sensor was fine? I'll check the triac though, just in case Link to comment Share on other sites More sharing options...
alistermorton Posted January 7, 2016 Share Posted January 7, 2016 You'd have thought so, yes, but it might be worth checking. Link to comment Share on other sites More sharing options...
DrV Posted January 7, 2016 Share Posted January 7, 2016 Has it been recently worked on? The temp sensor is a thermocouple so if it is connected the wrong way round the control circuit will think it is getting colder rather than hotter as the unit warms up. Link to comment Share on other sites More sharing options...
gyro_gearloose Posted January 7, 2016 Author Share Posted January 7, 2016 Those two tiny bits of wire are a thermocouple? That explains a lot. I always wondered why there were two pieces of wire soldered to the copper tube, but now I know its a thermocouple it all makes sense. Basically, for those who don't know, a thermocouple is two pieces of dissimilar wire joined together at one end (or soldered to a conductor in the case of our hazer). When that join is heated a DC voltage is created between the two pieces of wire which is proportional to the temperature of the join in the wire. Yes, I know its a bit more complex than that, but this is meant to be the simple explanation :) I haven't disconnected the thermocouple, but I did unbolt the heater block so that I could clean out some burnt-on residue from the end of the copper tubing. I may well have damaged the wiring to the thermocouple when moving the heater block about, so I'll check that when I'm back at work on Saturday. If it turns out to be damaged wiring, can I just solder any breaks in the cable withe normal lead solder or will I need a new thermocouple? Also, since the thermocouple works on temperature difference between both ends rather than just temperature of one end, should I tape the cable to the fan casing to keep it cool? Thanks for your help Link to comment Share on other sites More sharing options...
DrV Posted January 7, 2016 Share Posted January 7, 2016 You won't be able to solder it. Just twist the ends together very tightly. It doesn't matter how warm the rest of the wire is - it all cancels out in the end. Explaining cold junctions is too much when I'm using one finger on a mobile! If you want to check the continuity with a meter it should show a dead short Dave Link to comment Share on other sites More sharing options...
timsabre Posted January 8, 2016 Share Posted January 8, 2016 I would agree with the blown triac theory. I have fixed quite a few Jem machines with this symptom and it is always the triac. There isn't much to go wrong with a thermocouple unless as you say you've broken the wire, but I think the machine would detect that on power up and refuse to heat, the Jem ones certainly do. Link to comment Share on other sites More sharing options...
gyro_gearloose Posted January 8, 2016 Author Share Posted January 8, 2016 I had a quick look at the main PCB yesterday and couldn't see a Triac, unless its the thing that looks like a DC linear voltage regulator. If it is that then it complicates things a little as its soldered to the PCB and attached to a heatsink. Can I test it while its still soldered in place? Link to comment Share on other sites More sharing options...
timsabre Posted January 8, 2016 Share Posted January 8, 2016 Yes it looks like a voltage regulator (TO220) or maybe the surface mount equivalent. You can meter the two left hand pins (A1-A2) to check for a shorted triac. Alternatively meter between the neutral side of the heating element and the incoming neutral. http://circuits.datasheetdir.com/305/BTB04-600SL-pinout.jpg Link to comment Share on other sites More sharing options...
KevinE Posted January 9, 2016 Share Posted January 9, 2016 There's something 'unique' about these heater blocks (heat exchangers) if memory serves me right which means the heater has to be mounted on insulators. If these break down or get dirty and hence leaky, it can create an earth reference for the thermocouple (as its spot welded directly to the tube) which confuses the temperature circuitry. Might be worth checking those. If the t/c has failed open it will show an error, if it fails short (away from the hot junction) then you'll get the symptoms you describe. A short on a thermocouple will create a new junction that will give the pcb the temperature reading at the site of the short...which may never get hot so the machine keeps trying to heat. The le maitres use a similar system but if it fails to see a predicted rate of rise of temperature it fails with an error, not sure if the unique has such a thing. But as others have already said, the triac is your first port of call...and when the boards out, check for splashes of fluid; its very conductive. Link to comment Share on other sites More sharing options...
gyro_gearloose Posted February 10, 2016 Author Share Posted February 10, 2016 I've finally had a chance to look deeper into the Triac on our Unique. With the multi-meter set to its lowest resistance scale we get no continuity between A1 and A2, we get a reading of 53.1 Ohms between A1 and the gate, and a reading of 51.9 Ohms between A1 and A2 if we short the gate to A2. All of the readings stay the same regardless of whether I use the positive or negative multi-meter lead on A1. All of this would lead me to conclude that the Triac is fine. One thing I did notice was that the neutral side of the heater is connected to the incoming neutral. The Triac appears to be between the incoming live and the heater. Is this normal, or does it not matter? Up until the start of the current problem the hazer has always worked perfectly well, and since the Triac also appears to be fine I'm guessing that having the Triac on the live side is also fine? Link to comment Share on other sites More sharing options...
timsabre Posted February 10, 2016 Share Posted February 10, 2016 One thing I did notice was that the neutral side of the heater is connected to the incoming neutral. The Triac appears to be between the incoming live and the heater. Is this normal, or does it not matter? Up until the start of the current problem the hazer has always worked perfectly well, and since the Triac also appears to be fine I'm guessing that having the Triac on the live side is also fine? It's unusual to have the triac on the live side because it makes generating the gate voltage more complicated, but it is possible.Are you sure there has not been any mistaken wire swapping during disassembly? Link to comment Share on other sites More sharing options...
gyro_gearloose Posted February 10, 2016 Author Share Posted February 10, 2016 No, or if there was it was done before we got the machine. I know I can't have swapped any wires over as I have not removed any from the board. Looking at the connector block which runs down the right hand edge of the large PCB ours is wired like this from the top: Air pump neutral, air pump live, fluid pump live, fluid pump neutral, incoming live, incoming neutral, incoming earth, chassis earth, chassis earth, chassis earth, fan brown, fan black, fan blue, heater neutral, and finally heater live. Does anyone have a Unique 2 they can compare this with? Link to comment Share on other sites More sharing options...
graemeftv Posted February 23, 2016 Share Posted February 23, 2016 hi feel free to call me and I can provide you with the tech support you need. thanks graeme Link to comment Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.