>
>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?
>
>In response to queries by members of the group, yes, I had already made Rich
>Measures 110V bias mod.
>
>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.
? To find out whether the 0.82 ohm grid-I meter shunt resistor was
damaged by an interelectrode gas flashover or damaged by a parasite, I
would high-pot. the tubes at 2x the rated anode potential. If a tube is
gassy, the leakage will be fairly obvious in a darkened room. .
Measuring the resistance of the supp. resistors might be interesting too.
>
>I must say that mods I have done have at least prevented widespread damage
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