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Ceramic strips: Difference between revisions
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[[File:Tek ceramic strips 6.jpg|thumb|350px|right|Tek ceramic strips]] | [[File:Tek ceramic strips 6.jpg|thumb|350px|right|Tek ceramic strips]] | ||
Some Tektronix instruments use '''ceramic strips with metallized grooves''' to hold components and wiring. | Some Tektronix instruments use '''ceramic strips with metallized grooves''' to hold components and wiring. | ||
This started with the [[315|Type 315]] in 1952 | This started with the [[315|Type 315]] in 1952 – Tektronix engineer [[Frank Hood]] recollects: | ||
<blockquote> | <blockquote> | ||
Another employee, [[Ted Goodfellow]], a musician with ceramics as a hobby, suggested making a ceramic strip with silvered notches to act as insulator and support for the components. | Another employee, [[Ted Goodfellow]], a musician with ceramics as a hobby, suggested making a ceramic strip with silvered notches to act as insulator and support for the components. | ||
</blockquote> | </blockquote> | ||
The use of ceramic strips continued into the early 7000-series instruments such as the [[7514]] mainframe and [[7A18]] vertical plug-in, | |||
both of which were [[introduced in 1971]]. A late example is the [[465B]] from 1980 that uses these | both of which were [[introduced in 1971]]. A late example is the [[465B]] from 1980 that uses these strips in the HV section. | ||
Two distinct types of ceramic strips have been used in Tektronix instruments. | Two distinct types of rectangular ceramic strips have been used in Tektronix instruments. | ||
The earlier wedge type used a nut and bolt to mount it to the chassis. | The earlier wedge type used a nut and bolt to mount it to the chassis (see illustrations in [[Patent US 2836807A|US Patent 2,836,807]] which also include the [[Media:Tek_524_round_terminal_strip.jpg|cylindrical variety]] used in the [[524]]). | ||
The later rectangular style uses [[Patent US 3022973A| | The later rectangular style uses plastic snap-in clips (see [[Patent US 3022973A|US Patent 3,022,973]]). | ||
The production method is discussed in [[Patent US 3121020A|US Patent #3,121,020]]. | The production method is discussed in [[Patent US 3121020A|US Patent #3,121,020]]. | ||
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The ceramic strips turned out to be quite reliable. | The ceramic strips turned out to be quite reliable. | ||
If they aren't abused, the only known failure mode is when they are used in HV supplies and are allowed to get very dirty. | If they aren't abused, the only known failure mode is when they are used in HV supplies and are allowed to get very dirty. | ||
The dirt can become conductive, resulting in unintended current flow over the surface of the ceramic strip, and/or arcing. | The dirt can become conductive, resulting in unintended current flow over the surface of the ceramic strip, silver migration, and/or arcing. | ||
Once arcing occurs, heat from the arc would fire the silver into the ceramic, causing a permanent short that cannot be reliably cleared – such a strip must be replaced. | |||
This can be avoided by keeping the HV circuit clean, particularly the nodes after the rectifier(s). | This can be avoided by keeping the HV circuit clean, particularly the nodes after the rectifier(s). | ||