Finding the fault in this circuit (UV lamp controller)

[engnrshyckh]

TL;DR Summary

Guys this circuit and shematic is of UV lamp controller.. It burns sometime as shown in figure can someone tell the reason?

Guys this circuit and shematic is of UV lamp controller.. It burns sometime as shown in figure can someone tell the reason?

 

[jim mcnamara]

Is this a one time failure? From your description, 'sometimes it burns', does this mean it has happened with a replacement controller, too? Do you have UV lamp specifications you can let us see?

 

[Tom.G]

Summary:: Guys this circuit and shematic is of UV lamp controller.. It burns sometime as shown in figure can someone tell the reason?

It burns sometime as shown in figure can someone tell the reason?

Several possibilities:

• Load is too heavy (wrong lamps? high humidity?))
• Running without a load
• C6 bad
• Transformer has shorted turn(s)
• A resistor has changed value (looks like they have overheated, replace 'em)
• Supply voltage is (occassionally?) too high
• High ambient temperature
• Bad design (parts under-rated for the use)

The above is roughly in order of probability. (unless it is a third-world design with a very low price; then the bad design is most likely. )
Likely a few more "maybe's."

From the looks of them, those transistors have failed shorted. Which could be temperature related (overload, shorted transformer, shorted C6) or from voltage spikes (running no-load, or open C6). Could also be a bad resistor.

Cheers,
Tom

 

[berkeman]

@engnrshyckh -- The schematic looks a bit amateurish. Is this a home-brew circuit? Did you design it? If not, where did you get it and the schematic?