Old oscilloscope help: ideas sought

I know, bad form to follow up to myself.... ...I turned out to be in luck. On closer examination, this 'scope has a bank of screw terminals which are labeled (in black-on-dark-brown, not obvious except on close inspection) as being suitable for jumpering in certain ways to get the X and Y deflection plates as coming direct from inputs or coming from the X and Y deflection amplifier circuitry. I removed the insulator panel on which these terminals are mounted, and it is clear that four of the terminals go directly to the deflection plates (two for each axis), with a resistor (4.7M) hardwired from there to the deflection-amplifier terminals. (The direct-input terminals are capacitor-coupled to the plates if the jumpers are in the direct-input positions; if the jumpers are in the amplifier-fed positions, they short out these resistors, with the direct-input terminals doing nothing at all.) So I removed the jumpers entirely and, using alligator clip leads, grounded both X deflector plates (to the chassis, that being where all other grounds go). Voila, I can find the trace! (Well, spot, under the circumstances.) Using a voltmeter on the amplifier-output terminals indicates that one is driving about +100V and the other about +400V (of course, these may be reading low because of meter impedance, but they clearly are nowhere near equal). Grounding the deflection plate corresponding to the +400V line and leaving the other alone gives me a spot near one edge of the display; the other way around and I get the symptom I wrote about. So now it's just a matter of tracing circuitry back until I find the problem. (Heh. "Just".) Sorry to bother everyone when the answer was right there waiting to be discovered all the time. /~\ The ASCII der Mouse \ / Ribbon Campaign X Against HTML mouse at rodents.montreal.qc.ca / \ Email! 7D C8 61 52 5D E7 2D 39 4E F1 31 3E E8 B3 27 4B