[Test-Equipment] Tunnel Diode

[Richard]

hello Jeff,

Almost any TD of the same or similar current-rating has a very good 
chance of working just fine.

A TD's speed is directly proportional to its current-rating.

In other words, if yours is a 4.7ma TD, then one of the standard JEDEC 
number TD's with a spec of 4.7ma will likely work just fine. (I think 
they're a 1N3716 series, or something like that....both GE and RCA made 
them; among others).

Somewhere in your Heath manual, it likely mentions the current spec; at 
least indirectly.....in the section on adjusting the TD bias.  (I don't 
know that instrument, but almost anything that uses a TD had a 
bias-setting).

If there's absolutely no mention of it; then you might get an idea by 
measuring the existing bias-current setting.  Measure the voltage-drop 
across a resistor that's in series with the TD.....there'll very likely 
be one of those.  If the TD is missing, then put a Ge or GaAs diode in 
that spot for the purpose of measuring the Vdrop across the R.  ....and 
hope that whoever had it before you didn't mess with the bias 
setting....lol...

Note that many older Tek and HP scopes used a TD or two in the trigger 
and sweep sections.....and virtually all "sampling sweep" plugins will 
contain half a dozen TD's.  The HP 1400 series units are available for 
next to nothing (except for the shipping.....hi) so you might research 
those (full manuals probably available right on HP's site) and then snag 
one cheap.

hope this helps a bit,

Richard, KC0FVV
http://www.oregonstone.com/forsale-te.html


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