OT: O'Scope

It's been a while since I've opened up a 475, but all the connections to the CRT are via the socket at the rear of the tube. You can access that without removing the mu metal shield around the tube. It isn't built like a TV picture tube, there are no voltages external to be envelope except at the socket.

If for some reason you do want to remove the tube, unplug the socket, remove the bezel and faceplace, loosen the clamp, and the tube comes out the front. Note, I don't believe that Tek offers spare CRTs for the 400 series scopes anymore, so don't break yours.

Usually when there's arcing in these scopes, it is in the HV power supply, not at the CRT.

Gary

There is an outfit up in Canada, I think it is Spheres ?? that has all kinds of tubes for Tek and HP scopes.

JohnL sends...

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All kinds of cool stuff. A few years ago I sold them some weird avionics I got in a Gaylord full of junk at a DRMO auction and listed on ebay.

Ned Simmons

Yeah, good outfit, but they don't have any 475 CRTs, and say they have only gotten one used tube in the past year, and that one's been sold.

Gary

I hate to say it, but the problem may be in the HV supply. This is usually in a small plastic box under a small aluminum plate. I know

453s and 454s, so 475 may be different. A common problem is the old HV transformers arcing internally when they get warm. If it's the transformer, you're dead. The saving grace is that you can replace the whole scope for $100. As I recall, a guy in OR named Dean Kidd was a good source of parts. You might find him with a Google search.

Of course a common TV repair trick is to pull the covers off and turn it on in the dark. You can usually see the arcing even if it's very faint. I've even been able to see it several windings down inside the HV transformer.

Thanks, I'll try turning it on in the dark.

Tim