82: Difference between revisions

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a low controlled impedance (93 ohms), as opposed to other 500-series scopes  
a low controlled impedance (93 ohms), as opposed to other 500-series scopes  
that present a high impedance to the plug-in.
that present a high impedance to the plug-in.
Stan Griffiths wrote:
<blockquote>
If you feed [a fast risetime] signal into an early type 82, you will
find that the top three least sensitive positions have really terrible frequency
response . . . so bad, in fact, that some customers thought they were broken.
When told this was normal, these customers wondered why Tek ever included them
on the plugin. The answer was that they were still useful for low frequency
signals . . . but Tek never really made it well known that these 82 attenuator
positions were lousey. I think this was fixed on the later 82's as Tek learned
how to make better attenuators. If you have an early 82 and need to look at
high frequency signals on the less sensitive ranges, the answer is to get X100
probes and use them on the more sensitive ranges where the frequency response is
better.
</blockquote>


* [http://w140.com/tek-82.pdf Tektronix Type 82 Manual (PDF)]
* [http://w140.com/tek-82.pdf Tektronix Type 82 Manual (PDF)]

Revision as of 20:30, 1 August 2012

The Tektronix Type 82 is a dual-trace plug-in for the 580-series scopes. The Type 82 combined with a 585 or 585A provides a 4 nanosecond risetime. The front end of the Type 82 is a 7586 nuvistor cathode-follower, followed by bipolar diff-amps and diode channel switching, followed by a distributed output amplifier made of three 6DJ8 tubes, with differential 93-ohm outputs. The use of a distributed amplifier in a plug-in is unusual. Note that the 58x series differs from 500-series scopes mainly in that the vertical signal interface between the plug-in and the mainframe is a low controlled impedance (93 ohms), as opposed to other 500-series scopes that present a high impedance to the plug-in.

Stan Griffiths wrote:

If you feed [a fast risetime] signal into an early type 82, you will find that the top three least sensitive positions have really terrible frequency response . . . so bad, in fact, that some customers thought they were broken. When told this was normal, these customers wondered why Tek ever included them on the plugin. The answer was that they were still useful for low frequency signals . . . but Tek never really made it well known that these 82 attenuator positions were lousey. I think this was fixed on the later 82's as Tek learned how to make better attenuators. If you have an early 82 and need to look at high frequency signals on the less sensitive ranges, the answer is to get X100 probes and use them on the more sensitive ranges where the frequency response is better.