pathfinder blown power transistor

[woofhead]

Hi,

I'm replacing a blown power transistor on my vox pathfinder(It's a TDA2030-found the info with a search on this board-thanks!)I think I blew it out using the amp to drive another cabinet(12" speaker) and I'm wondering how to avoid this problem in the future.As far as I can remember the cab I was driving was the same ohmage but I think I was connecting them with a guitar cable-could this have been the problem?The amp started smoking and did not turn off so the fuse did not blow right away. Any insight would be appreciated as I'd love to learn more about why this happened.Thanks a lot,

Mike

[antilog]

You should use speaker cable, which uses speaker wire - 2 conductors (hot, ground) running alongside each other. Guitar cable uses shielded wire - hot conductor running inside of the ground conductor (shielding).

Shielded is for low power signals, unshielded for high power.

Shielded cable has more capacitance, which increases the impedance that the power section of your amp "sees".

I am not positive this caused your problem, but it may be a good idea to use speaker cable in the future regardless.

[Milkmansound]

transistors blow when they see too many square waves - aka, too loud.

However, it could have been something else like a dip in the power supply, or a spike, or just a faulty transistor, or something else taking it out.

Keep an eye on your impedance, and make sure its not distorting (when its not supposed to be)

[woofhead]

Hi agaian(from Canada),

Thanks for the tips so far-I really appreciate it! Great to learn something

Mike

[antilog]

there's some amazing people here to learn from, and if you do the work on your end to research things, most are glad to help you out...

lots to learn, this board has helped my engineering and my art.