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I think you might be able to get one of these 3-conductor BNC sockets from Qservice or Sphere. It is described in the Service Manual as "connector, Rcpt,: BNC, Male, 3-contact", the Tek p/n is 131-0679-02 and it was originally made by Specialty Connector Co., of Indianapolis. Good luck with replacing it, though, I wanted to replace one where the factor-switching connector had come adrift . I gave up eventually, as it seemed that you need to remove more stuff than seemed sane to just to get at it. I tried making a thin-wall socket to loosen the nut and that failed, too. I eventually drilled a small hole through the sensing-ring, poked a bit if tinned-copper wire insulated with sleeving and soldered it to the sensing-ring. It worked.
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I don't know where you got the information that the 43R resistor is described by Tek as carbon film - my 475A Service Manual describes it as "Res., Fxd, cmpsn: 43 Ohm, 5%, 0.25W" which I read as "carbon composition", as is its analogue in the other channel. Colin. -----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of Torch Sent: 31 January 2021 20:40 To: [email protected] Subject: Re: [TekScopes] Sloppy front panel BNC connector - 475 Thanks everyone who replied. The 475 connector body (ie: the part that incorporates the outer, probe sense, ring is secured firmly to the front panel with a nut. The nut is not loose and won't move under power of needle nose pliers (it would require some sort of really thin wall socket, I think). Between that outer ring and the next "ring" (ie: the BNC shield proper) is a layer of nylon(?) insulation. It is that layer that is loose, allowing the entire BNC portion of the connector to float within the body. I can look all the way around using a mirror, and don't see any sign of a set screw. Unless it is under the nut, I don't see where one could be. If anyone knows the part number or a source for the style 3-conductor BNC assembly used on the 475 front panel, I'd love to replace it. In the meantime, as a temporary fix, I stood the chassis gently on it's nose so the connector was vertical with access to the back, and drizzled in a few drops of thin cyanoacrylate. I wiggled and jiggled the connector to work the cyano in as deep as I could before letting it sit and set up. That firmed things up mechanically -- for now, anyway. That leaves the resistor. So much debate about a 10? part. Probably every single one of you knows more than I about the subject. I suspect a couple of you have forgotten more than I know about the subject. So when one of you says that a carbon composite is a better choice for this application, I think it's worth listening. That said, after careful consideration, I decided to stick with the original Tek-speced carbon film resistor. I don't use this for any high-energy measurements. I mostly use it for things like transistor curve tracing (my digital scope is great but sucks at XY display) combined with a personal bias towards restoring old equipment as opposed to modifying old equipment. But thankyou again for the input. |
