OT: Semi-functional scope?

From: Allison J Parent <allisonp_at_world.std.com>
Date: Tue Sep 21 20:46:12 1999

<> prevents rapid deflection changes. However, electrostatic deflection is
<> more limited in the achievable deflection angle, so a longer tube is
<> required.
<Also, a narrow deflection angle will improve linearity, which is
<obviously very important in a measuring instrument...

Length of the tube was a function of deflection sensitivity, minimal effect
on linearity directly. The linearity improvemnt was the flatter crt face
as a result of the larger radius.

<For anything higher you need electrostatic deflection, though. High speed
<electromagnetic deflection would involve very high voltages in the
<deflection amplifier output stages to overcome the back EMF from the
<deflection coils.

No, the inductance. You need a certain amount of current to move the beam
and at higher frequencies the inductance of the yoke is the limiting factor
in attaining that current. Faster electromagnetic scopes used very high
amperes to turns ratios to keep the inductance to tolerable levels.

For electrostatic tubes the capacitance of the plates combined with the
leads (internal and external) were less limiting though above 20mhz or so
they become very significant.

However this helps lordtyran not one bit.

Likely the problem he has is twofold, lack of experice using O'scopes
and possibly a major balance problem due to internal misadjustment or
component failure. We also have no idea if this is a low end recurrent
sweep 5mhz cheapie or a triggered sweep cheapie. this would influence
what suggestions could be made.

Received on Tue Sep 21 1999 - 20:46:12 BST

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