Exploded transistor

[stj]

Re: Exploded transistor

the resistor is usually inside thick tubing.
and i'v never seen a bad transistor, just bad caps and open heaters.

maybe the 110v lamps stress the transistors harder.

[jasonbay13]

Re: Exploded transistor

so status update. i replaced the blown transistor with a c1815, and the c5027 switching npn was infinite resistance through all combinations on my meter. replaced that with a 13007. plugged it in and it has voltage to the 5v. but it was making a clicking noise, kinda like the rad meter on fallout :P, whats it called a geiger counter? i unplugged it after that in fear of exposions. any reason its ticking?

[ben7]

Re: Exploded transistor

so status update. i replaced the blown transistor with a c1815, and the c5027 switching npn was infinite resistance through all combinations on my meter. replaced that with a 13007. plugged it in and it has voltage to the 5v. but it was making a clicking noise, kinda like the rad meter on fallout :P, whats it called a geiger counter? i unplugged it after that in fear of exposions. any reason its ticking?

It might be ticking because of a short circuit. Check to make sure none of the secondary side rectifiers have been damaged (shorted) from the catastrophic transistor failure.

[stj]

Re: Exploded transistor

check any ceramic caps for shorts too.

[jasonbay13]

Re: Exploded transistor

so anyway, i grounded ps_on and checked the 12v voltage, whilst it clicking away. measured 12.1vdc and 25vac. might this be a shorted rectifier as ben7 has suggested?

[ben7]

Re: Exploded transistor

so anyway, i grounded ps_on and checked the 12v voltage, whilst it clicking away. measured 12.1vdc and 25vac. might this be a shorted rectifier as ben7 has suggested?

What about the other voltages? It might be instability because of a low load on one of the voltage outputs. That leads to my question, do you have a load on the PSU now?

Edit: Well, not instability, but rather a very low duty cycle.

[jasonbay13]

Re: Exploded transistor

no, i had taken the fan off to keep it out of the way, and it didnt work anyway. the fan might have made it click a little slower, but it sounds like it is coming from possibly one of the 2 transistors i replaced. though my meter is not trms, so i dont know if that 25vac is actually accurate or not.

i could hook it up to my scope though.

[ben7]

Re: Exploded transistor

no, i had taken the fan off to keep it out of the way, and it didnt work anyway. the fan might have made it click a little slower, but it sounds like it is coming from possibly one of the 2 transistors i replaced. though my meter is not trms, so i dont know if that 25vac is actually accurate or not.

i could hook it up to my scope though.

The ticking might actually be coming from the transformer. That is typical when a switch mode power supply runs at a low duty cycle (because of a very light/non-existent load).

Try putting a load on it and see if the ticking goes away.
Otherwise, it's possible the ticking could be coming from a snubber capacitor that is breaking down.

[stj]

Re: Exploded transistor

why not just check the rectifiers, diodes and ceramic caps while it's off, instead of stressing the transistors in a way that may kill them!

[ben7]

Re: Exploded transistor

Well yes, there is that approach as well :P