A few newbie questions (Scott 299-d)

[erichayes]

Hi All,

Vintage Scott gear, particularly the gold face stuff like the 299, don't need to be brought up on a variac, as it is a virtual certainty that every one of the electrolytics is open. This includes the low voltage one used for the bias and preamp heater supply, and any bypass caps in the preamp. Fortunately, new axial lead caps are small enough to sneak under the shallow chassis, although you have to be a little creative on placement--you can't always get them close to the original can. Doing this allows the original skyline of the amp to remain unchanged.

Changing the coupling caps between the phase inverter and output stages is also a good idea regardless of type. Oil and paper caps go leaky, and ceramic caps sound like Hell. Other non-electrolytic caps generally don't fail in an epidemic fashion, but don't hesitate replacing any cap that shows any physical sign of leakage. New tubular caps are no longer "polarized" either, so you can ignore the black band or "outside foil" markings on the old ones when replacing.

Since carbon composition resistors are sensitive to heat--both internally and externally generated--any comp. power resistors should be checked and replaced as needed, as well as any ½ watters that are in or around the power supply and output sections.

Because Scott used aluminum chassis, and because they were so shallow, they tended to spread the heat throughout the amplifier more than conventional depth steel chassis do. This is one reason the electrolytic caps all failed, and why you have to search more thoroughly for thermally related problems.