[Amps] SB-220 cap arc and the local broadcast station

[Tom Rauch]

> I tried all the cleaning, de-burring type tricks before I
> bought the late version cap. In my opinion, lack of
> proper parasitic suppression and an otherwise eager
> capacitor caused the previous owner (two different
> brands of) tube failures.

You can not clean and polish a capacitor and restore voltage.

Although the article mostly was written for gamma matching, I give sme
details why in my gamma and omega matching page.

Capacitors are micropolished, the general procedure is plates are roughly
deburred and then tumbled in walnut shells.

> After the standard updates were in place (which
> include my own type of suppressors), full tilt key-
> down into the load didn't even touch weak signals
> into the adjacent FM receiver.  Sometimes the
> music stinks, but it's not the amplifiers problem...

Most FM receiver problems are through power line or direct radiation into
receiver IF systems. They are particularly sensitive to 7 and 14MHz signals,
since the IF's are at 10.7

Tighten a screw, move a cable, and the problem changes.

I have Motorola Micor 147 MHz repeater here, and when it was in my workshop
my 7 and 14MHz signals would totally wipe out the receiver, opening the
squelch when no 2m signals were present. My cure was to unplug the phone
line to the repeater, and reroute it slightly.

73 Tom