Re: 7A21N question

Miroslav Pokorni

No Craig,

That unattached board is to replace vertical amplifier in your scope and
it's output attaches directly to deflection plates. The 7A21N is just a
carrier for board, as well as for small ceramic based hybrid (located on
main board, towards front panel). That hybrid replaces CRT termination and
facilitates trace position. The connection for trace position goes through
that 4 pin connector on top rear of plug-in, almost never used by other
plugs. One of things in the baggy is a cable that goes from that 4 pin
connector to the hybrid. Note plastic clamp, screw and nut in the baggy, to
route the two wire cable.

As for single ended input, that is effected dynamically (in real time), by
inserting terminator to inverting input and using remaining one for input

So, do not rejoice at 1 GHz bandwidth, it takes a scope dedicated to that
purpose, unless you are going to play yo-yo with vertical amplifier and CRT.
It is an interesting gadget and before I knew much about it, I had to have
it. But now, I do not see mush use for it and it was never installed.


Miroslav Pokorni

----- Original Message -----
From: "Craig Sawyers" <>
To: "TekScopes" <>
Sent: Thursday, July 10, 2003 1:50 AM
Subject: [TekScopes] 7A21N question

Hi all

Just received a 7A21N direct access plugin. This has two GR connectors on
the front panel, and bypasses the input amplifiers, giving a stonking
bandwidth of 1GHz in a 79xx series scope, but with a fixed deflection
factor. Differential or single ended mode is selectable internally. And
here is the problem:

First, it is more complex internally than you (or I) might imagine. There
are delay lines, phase inverters, an rf bridge and a power divider in
plus other stuff. There is also a separate board with a number of
connections and components (but not connected to anything), clearly
to feature in the conversion between differential and single ended mode.
There was a baggie of accessories in there (yippee!) with a GR 50-ohm
two Tek-Tek coax cables, a couple of Tek-Tek coax adaptors, and a cable
use in the mainframe (unusually, this PI has two of the top rear
used to deliver power to the position control) with a harness clip and
mounting hardware.

Soooo - has anyone got one of these, and/or a manual?

Thanks in hope!


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