>Checked out the SB-220 this morning for damage. The only component that blew
>was the 0.82 ohm resistor. I noticed that the resistor is of the metal film
>type with a 2W rating, manufactured by Phillips. Heath manual calls for a
>wirewound resistor rated at 2W. When the original big blow happened last
>year, I had replaced Harbach's .82 ohm 3W WW with the 2W metal film type. Is
>this significant?
Don't know why a 2W wirewound would have more dissipation capability than
a 2W metal film. I'd put in a bigger wattage value anyhow if that's what
keeps blowing.
>
>In all the years that I spent working on high power transmitters, I have
>never witnessed a failure caused by a parasitic when the transmitter was
>powered but unkeyed. That's why I'm having a hard time accepting that the
>fault was caused by a parasitic. But, of course, that's not to say that its
>not possible.
Agreed. Everything bad that happens in amplifiers is not due solely to
parasitics. I belive this is NOT your problem, but rather that it sounds
like you just might need a higher wattage resistor.
73,
Jon
KE9NA
--------------------------------------------------------------------------
Jon Ogden
jono@enteract.com
www.qsl.net/ke9na
"A life lived in fear is a life half lived."
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