What would cause the Choke on my amp to fry?

[leadfootdriver]

I was playing the 2:90 and the sound cut out for a split scond, and then it blew the main fuse and then I smelled it. :evil: It smelled like a plastic barbecue. It was the choke. It tested it for resistance, and there was none, so I guess the circuit inside fried open. Why did this happen?

 

[Blueracer]

Sorry to hear about your 2:90. The melted plastic smell, the fuse blowing and the choke being an open circuit all indicate excessive current. My guess would be an internal short to ground in the choke since you don't see any other damaged componets. Kind of hard to say what would cause this without doing a replacement and seeing if there are any other problems in the amp that would have stressed the choke.

 

[Martin]

The windings in the choke must have melted. It should have a very low resistance but not zero or open circuit.
Blueracer is correct, something is drawing too much current ?...are your speaker's ok, hopefully there was no DC at the output to damage them.

 

[leadfootdriver]

Thanks for the input guys! I talked to a tech, and he said he never heard of a choke checking out, but that high current was the issue. Also, he said power tubes blow in different ways, so even though my high tension fuses didn't blow, a bad power tube could still take out the main fuse.

I just ordered one from Mesa for $15+shipping, so hopefully this will fix it. I also ordered new JJ power tubes.

 

[AdmiralB]

The HT fuses in the 2:90 are on the power tube cathodes (a rather stupid design, IMO), so if the current passes elsewhere - in the preamp, for example - the HT fuses are useless.

 

[steeeeeeeeeevo]

My new 2;90 just had a plastic barbaque aswell but its under warrenty so I cant look inside. So what was the problem or what got repaired?

cheers