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amdx[_3_]

On 3/6/2014 3:58 AM, wrote:
I can't believe this.

the terminals for the deflection plates are dual. The deflection plates run on voltage, not current.

The 165 ohm resistors are simply pulling the output up to the +53 volt supply.

We are now on the same page.

The fact that HP decided to

put the 165 ohm resistors on the other connections to the deflection plates is irrelevant as far as I can see,

the only reasons are quite esoteric and beyond the scope of this discussion obviously.

It is what it is.

If you are trying to claim that this CRT uses some form of electromagnetic deflection rather than electrostatic,

state your case.

I don't have a case, I'm just looking at the schematic. I don't think
it is electromagnetic, I don't think that would be fast enough. Hmm, can
you do an inductance test? A resistance test will be near zero ohms
whether it is a plate or a coil.
It is still all confusing because of the mod that we know, it uses
high current devices. But that seems wrong when you see the 165 ohms in
series with the deflection (plate).

I can't say it is not true for sure. I said I do not know why they used
the two connections per

deflection plate, because as a rule they do operate electrostatically. If this CRT works on a different principle, say so.

I'm as confused as you. The label says Plate, the drawing is a coil.
And, why is the voltage labeled +53.3VF?

I believe this arrangement with the plates its mainly to reduce and/or reject EMI. Either that or to eliminate or use

standing waves in the plates themselves, which I find unlikely because they are too small.

I could be wrong, but I understand how this **** works, until I don't. Claim it works other than electrostatically or don't.

If I am wrong, fine, but until then it is a voltage amplifier only. It only has to overcome the capacitance of the load,

which is the deflection plates. The low resistance 165 ohms is to provide a low output impedance to this effect.

If I am wrong, explain. tell me the difference between this and most other eletrostatically deflected CRTs.

I don't know.

A question for you, assume for a moment it is electrostatic, I would
think only one plate is energized at a time. There is no negative drive
for the other plate, to drive the beam the plates would need to have
opposite polarity OR only one plate is driven at a time. (I think only
one plate is driven at a time)
If it was electromagnetic, then the leads could reversed on one coil
to develop the opposite drive.
Do you have another dual trace scope to look at the drive to the
defective IC? Pin 7 and Pin 5. I don't know, you might need to open the
circuit to the defective IC. Also have you checked that R26 (31.6 ohm)
resistor? I see at least one person had that problem.
Mikek
PS. see if you can find waveforms on a schematic, might save you from
checking it with your scope.