Hi all,
I'm now working on a different Philips scope which 'died' suddenly for no apparent reason. Here's a summary of the key points:
The smps section had power in, but nothing coming out. I checked the smps outputs for shorts/low-res. One output marked 45V was trying to feed a board with an input resistance of only 6 ohms. I located the board in question. There were several multi-pin connectors around the edge of it running off to other parts of the scope. Now it turns out the smps runs perfectly fine when *one* of these connectors is pulled from the board. With the suspect connector's plug disconnected, the aforementioned 6 ohms shoots up to about 15k and life is great.
*BUT* (and here's the thing) the resistance looking into the suspect plug (which has only two wires) is several megohms. And yet this very high resistance, when plugged into the board causes such a voltage drop that the smps shuts down! How is this even possible? I keep thinking there must be something simple I've overlooked, but can't think what it might be. If anyone has experienced something similar in the past and remembers what the underlying issue was, then that could be very helpful! Thanks.