Subsitute Q3 on Hammerhead

[Ray Huffman]

I was wondering if you can subsitute an NPN high voltage transistor used in a television for Q3, specs say 1500v c to e and 1 amp collector current. I had to subsitute a IRF540 from Radio Shack since they do not carry the IRF740 and its only good to 100v. I stuck a 2 ohm resistor in series with power to the coil to current limit it and reduce the flyback voltage just so I could have something to experiment and learn with. Also just breadboarded each section on seperate bds so I can swap out easily and changes with out redoing the whole thing.
Ray

[Carl-NC]

Re: Subsitute Q3 on Hammerhead

Should work fine, just watch the current, although a "1 amp" rating is usually for continuous current, so you can probably exceed that in a pulsed application.

- Carl

[Gary]

Re: Subsitute Q3 on Hammerhead

A transistor will work, but the "On" Resistance isn't nearly as good as the IRF740.
I can supply you with the IRF740 for $3.00, Including Postage cost, If your interested.

Merry Christmas.......Gary