[...] It's an old trick, like using the working channel of a stereo audio amplifier as a comparision for the defective one. Or using one beam of a 'scope to find fualts in the circuits for the other beam (Tektronix suggest this...) But it's best not to swap parts between the 2 identical sections unless you know what you are doing. Particularly in power amplifiers where a fault in the driver stanges can damage the output devices. Swapping the driver boards over can make you end up with no good output transistors, and assorted other blown components.. An electromagentic CRT will have a deflection yoke -- coils -- fitted around the CRT neck. An electrostatic CRT won't, the deflection is achieved by internal deflection plates (electrodes), but you might find pins coming through the glass neck just behind the flare with wires connected to them (this is to get a short, low-inductance, conenction to the plates. An electrostatic CRT will normally have a smaller deflection angle (and thus a longer neck for a given screen size) than an electormagnetic CRT. In geenraly it's easier to get a good high frequency response from an electrostatic CRT. Which is why most (if not all) analouge 'scopes are of this type. Vector XY displays can be either -- for example the DEC ones tend to be electromagneitc, the HP ones electrostatic. 'Amplifier' sounds OK to me. It owuld be interesting to know at what point in the circuit the deflection controls operate. It may not be part of the output stage. In which case you know the stages after the deflection cotnrol are working fine. My first thought (although I can't really see why) is some kind of push-pull stange where only one device is working correctly. But as you know by know, withoug a scheamtic it's going to be hard to find... -tony