852D+ Hot Air Station - Temperature doesn’t increase

[ohmmy]

The dial lets me change the temperature setting but it always stays at 006. I’ve tried replacing the heater element (even though original tested fine) and no difference. Air flow still works fine. Any ideas?

[Wedgehog-uk]

Hi mate, the heating element will probably be driven by a Triac and I think the Triac's gate is controlled by that little white six pin opto triac U5 the triac will be the thing bolted to that black heat sink.
So check the power is getting to it ok first, there may be a fuse or low value resistor in line with it which mifgt be O/C if it is ok check the Power Triac, if that's ok look at the small white opto triac and the gate control circuitry, you should be able to find a circuit diagram online, any circuit for this range of models would be workable as they are all similar wheni it comes to the heater drive.

[ohmmy]

Hi mate, the heating element will probably be driven by a Triac and I think the Triac's gate is controlled by that little white six pin opto triac U5 the triac will be the thing bolted to that black heat sink.
So check the power is getting to it ok first, there may be a fuse or low value resistor in line with it which mifgt be O/C if it is ok check the Power Triac, if that's ok look at the small white opto triac and the gate control circuitry, you should be able to find a circuit diagram online, any circuit for this range of models would be workable as they are all similar wheni it comes to the heater drive.

Thanks. What voltage should I be looking for at the Triac gate?

[Wedgehog-uk]

Thanks. What voltage should I be looking for at the Triac gate?

Wouldn't worry too much about the gate yet as I think your fault will be before you get to that, but if you do it will be a much lower voltage, not sure exactly. concentrate on one side of the mains should be directly on one side of the heater element, the other is switched by the triac and controlled by the triac to give the set temp. the faults are always with the higher voltage and higher power stuff, the Triac on the heatsink may be open circuit, or no mains voltage on it due to a burnt out fuse or resistor.
Here is a circuit of a similar one, hopefully will give you an idea of what's going on, the heater element bit is probably pretty much the same.

[ohmmy]

Wouldn't worry too much about the gate yet as I think your fault will be before you get to that, but if you do it will be a much lower voltage, not sure exactly. concentrate on one side of the mains should be directly on one side of the heater element, the other is switched by the triac and controlled by the triac to give the set temp. the faults are always with the higher voltage and higher power stuff, the Triac on the heatsink may be open circuit, or no mains voltage on it due to a burnt out fuse or resistor.
Here is a circuit of a similar one, hopefully will give you an idea of what's going on, the heater element bit is probably pretty much the same.

Thanks I’ll check some stuff. Btw the soldering iron section still works. Not sure if they both work off same mains power or not but maybe it’s a clue?

[sam_sam_sam]

I would check both optic sensors and the triggering relay for the gun and make sure that it triggers the relay and you have output voltage on it

[Wedgehog-uk]

Thanks I’ll check some stuff. Btw the soldering iron section still works. Not sure if they both work off same mains power or not but maybe it’s a clue?

Hi, The Iron working is a good signe and says there is poweron the board, but as to whether it gets to theelement is another thing, you need to do some testing, we cannot diagnose it from here, only give you advise where to look, let me know how you get on and what you find and it should lead to an eventual diagnosis, also look at what Sam has said. Bob

[redwire]

In the pic, the one triac BT137-600E at the board bottom, the front is dark, it might have roasted and gone open-circuit. Tiny heatsink, they run quite hot and usually short circuit and burn the house down, start a fire. If replacing, buy a top quality part. If you can carefully bridge the MT1, MT2 pins and see if you get heat. Or use a multimeter on Continuity mode and beep out the connections from heater to the triac.

Small chance the microcontroller is refusing to turn on the heat because your temperature reading is wonky - "006" is not room temp and is kinda cold. That would be troubleshooting the thermocouple and op-amp.

[ohmmy]

So I haven’t hide time to really dig into this troubleshooting but I did just measure a few things visible without needing to remove the circuit board. I noticed D2 measures .139 both ways when testing in diode mode. Appears it or something connected to it may be shorted but it might be connected to the relay and wasn’t sure if that’s a normal reading if so? Before I dig any deeper the board seems like a pain to fully remove so wanted a little feedback. Thanks

[Wedgehog-uk]

So I haven't hide time to really dig into this troubleshooting but I did just measure a few things visible without needing to remove the circuit board. I noticed D2 measures .139 both ways when testing in diode mode. Appears it or something connected to it may be shorted but it might be connected to the relay and wasn't sure if that's a normal reading if so? Before I dig any deeper the board seems like a pain to fully remove so wanted a little feedback. Thanks

Hi mate, well it certainly doesn't look right, all I can say is you better investigate it, it's impossible to do from here :-) you are right though it could be the flyback protection diode across the relay coil, it's those Triacs you must check.

[redwire]

I would say that is a normal low (Vf) reading, the relay coil is in parallel to the diode. Not sure what the relay does, any idea?
Put a felt pen stripe mark or two or three, on the connectors so you don't mix them up or reverse them putting it back together. Take a few pics. Hardest part is the many connectors that look the same.

[ohmmy]

So I was checking continuity from all wires to the air nozzle to rule those out before digging the circuit board out and for fun I tried it again. It started to work! I then realized this power wire from the on/off switch going to wand looked very dull.

i unplugged it and turned it on, sure enough the original fault and 006 reading showed. So I got lucky with this one looks like just oxidation. I crimped the wire for better connection and reinserted.

It’s been working fine since. Hopefully that’s all it was for now. Thanks everyone appreciate the help!

[ohmmy]

Oh one other question, when I first replaced heating element this metal ring fell out while I was pulling element out. Not sure where it went or if it's needed? The heating element is wrapped with maybe myler paper or maybe something else? So it's shielded from the outside metal so not sure where this ring went or its purpose

[Wedgehog-uk]

So I was checking continuity from all wires to the air nozzle to rule those out before digging the circuit board out and for fun I tried it again. It started to work! I then realized this power wire from the on/off switch going to wand looked very dull.

i unplugged it and turned it on, sure enough the original fault and 006 reading showed. So I got lucky with this one looks like just oxidation. I crimped the wire for better connection and reinserted.

It’s been working fine since. Hopefully that’s all it was for now. Thanks everyone appreciate the help!

Hope so mate, sounds like you got lucky with that one, well done.

[ohmmy]

Oh one other question, when I first replaced heating element this metal ring fell out while I was pulling element out. Not sure where it went or if it's needed? The heating element is wrapped with maybe myler paper or maybe something else? So it's shielded from the outside metal so not sure where this ring went or its purpose

Anyone know what this is for?

[Wedgehog-uk]

Anyone know what this is for?

Sorry mate, I don't. I would imagine there are many kinds of elements and mine hasn't got a metal ring. God this image verification every time I write something is a pain, I have never seen such a thing on a forum in 30 years I've been using them!

[redwire]

It could be a crimp-ring for the air hose

[Wedgehog-uk]

It could be a crimp-ring for the air hose

Good thought mate