Working on a National 303, and I am having troubles. Foremost is B voltage (on two lines)that can drop, at some times 30 volts. Electrolytics are all fresh as are most capacitors. Can someone point me in the direction of checking for components that might be causing this drop? If it is a short, how can I check for it along the B line(s)?

Are there any resistors in series with the B+? Also check for cold solder joints.I usually use the tip of something non-metallic like a pencil barrel to poke around and look for mechanically induced changes.

Lou

:Working on a National 303, and I am having troubles. Foremost is B voltage (on two lines)that can drop, at some times 30 volts. Electrolytics are all fresh as are most capacitors. Can someone point me in the direction of checking for components that might be causing this drop? If it is a short, how can I check for it along the B line(s)?
:

Dirty pin sockets?

:Are there any resistors in series with the B+? Also check for cold solder joints.I usually use the tip of something non-metallic like a pencil barrel to poke around and look for mechanically induced changes.
:
:Lou
:
::Working on a National 303, and I am having troubles. Foremost is B voltage (on two lines)that can drop, at some times 30 volts. Electrolytics are all fresh as are most capacitors. Can someone point me in the direction of checking for components that might be causing this drop? If it is a short, how can I check for it along the B line(s)?
::
:
:

Poor ground points can also cause this. Check tube socket rings that are sometimes used as grounds. The rivets holding the socket may not make a good contact with chassis. Solder socket rings to chassis.