[ColinTheAmpMan1]

Hi Richard,

Its great to hear good news. Did you order the grub-screws with with sharp conical points or the cup-point ones? The latter are the correct ones, I think. I ordered 40 of those today and they are due to arrive tomorrow! What service!

That was a pretty good picture of the attenuator that you took. If you have a dead attenuator module, I might have a replacement if you know what the attenuation factor is (I have a parts-donor 466). I thought that I remembered MrB saying that he had some spares, too, or did I misread that?

You might have a misconception of the meaning of "auto" on the time-base trig mode switches. All it means is that in the absence of a vertical signal to trigger on, the time-base will free-run showing a horizontal line. In "norm", the time-base does not free-run and a blank screen is seen. The trigger level and slope controls operate in both modes. I can't think of much of a reason for the two modes, apart from preventing the phosphor from getting burnt-out when a bright horizontal line is displayed for a too-long time. I always turn the brightness down low if I'm leaving a scope unattended for any length of time, anyway.

I hope you don't have any problems with the dual timebase cam-switches, they are a real pig to make sure that the A and B time-base knobs are properly aligned. Also the pull-shaft for the delayed time-base can break in the middle.

Something else that I should have mentioned is that I now believe that my original ideas on the sequence of the parts of the filter were wrong. After looking at a number of manuals, it looks as though the filter element should be the outermost one and thus easy to remove and replace. I was convinced that I was right as my original fiddly solution quietened the fan noise down so much. I have now sorted out the filter on the 475A with DM44 that I "inherited" from MrB with the filter in the right place. At first, the noise came back and I wondered what I had done wrong, but with a bit more effort, I was able to fiddle with the position of the impeller on the fan-motor shaft. It has to be far enough out to not bind on anything, but close enough in to avoid touching the filter-housing and making a noise doing so. All a bit touch-and-go, but I think I have got there now and have a quiet fan (I hope).

Cheers, Colin.