BT139F triac replacement

[babawushika]

Hi everyone,

I used to design PCBs, but it was 15 years ago. Now I am in IT. I had a deducted evaporative cooling system. It has a PCB controller. Starting this summer (in Australia), when the temperature is not too high, it works fine. When it is really hot, it shuts down and the water valve cannot be properly opened, instead its solenoid has a high-frequency clicking sound. I had a look at the PCB, there are only two components that needs heat sinks. I replaced one, no effect. The other is this BT139F. I can't buy it locally. I bought one on ebay from UK, it was said to be BT139F600, but the actual chip sent to me was BT139X. Instead of a metal base, it is plastic. When I solder it onto the PCB and turned on the system, it went into the faulty "over-drive" mode straight-away - now it is autumn and the temperature was much lower. So this BT139X plastic chip was worse than the one I removed!

What is the component that can be used to replace BT139F, that is commonly and easily available? Better to be something that is even slightly more powerful than BT139F, that sustains more work load?

To order the whole PCB from the supplier costs AU$280, which is US$290. As someone who makes such PCBs I am a bit reluctant to surrender this much money while the solution might be $3 away. Please help!

Thanks!

 

[itsmoked]

I suspect there was nothing wrong with the one you had. Can you put it back in? Put a little fan on it or heat sink it much better than the original.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[babawushika]

It has to be - it had worked fine in many previous years in much hotter days.

 

[VEBill]

Sometimes it's not the component itself that's failed, but the thermal stresses might have cracked the solder joints (depends how it's mounted). The cracks might not be visible, but often are under a magnifying glass.

Triacs are not overly critical components. You could almost scavenge one from a cheap light dimmer.

Also, while keeping in mind the dangers of line voltage and 'hot' device mounting tabs, you might be able to install the replacement triac in a different location (using jumper wires). If you don't know what you're doing, don't attempt this.

You could perhaps also use the sacrificial light dimmer to test your suspect triac.

I can't stress enough how careful you need to be. And the importance of some basic knowledge.

 

[babawushika]

Thanks-do you know a replacement for BT139F?

 

[babawushika]

Can I replace BT139F with BT137F?

 

[rtronics]

No.
Try BTA16-600BWRG, from Element14, item number 1175636.
Ray.