CT-96 Adjustable temp soldering iron, circuit help..

[tkid]

Hi, I have a CT-96 adjustable temp soldering iron which works great initially, but after around 12 mths of intermittent use, it stopped working.. What i found was that the MAC97A8 Triac had failed, along with the LM358 op-amp had also failed.
Replacing these fixed it, for at least another 12mths!
What I would like, is if anyone is familiar with the circuit for these things, to suggest what else I could do to improve the reliability of the circuit to prevent the eventual failure of the MAC97A8 and LM358? I have attached photo showing both component and copper track sides, and if there is enough interest, I would be happy to map out the circuit and post as well.. Thanks in advance..

 

[(*steve*)]

What was the failure mode of the triac?

It might be useful to get a higher voltage rated triac.

It also might be useful to place a large MOV across the power connections inside the soldering iron.

You'll know if this works in about 13 months...

 

[tkid]

Thanks for the quick reply.. the Triac failed with shorts between MT1 and MT2 to Gate, measured around 150Ω resistance between them. I will look into getting a suitable upgrade to the triac, and maybe add a snubber network across it as well?

 

[(*steve*)]

The load is probably dominantly resistive, so I don't think you'll need a snubber network, but it can't hurt.