[Test-Equipment] Tunnel Diodes

[Barry L. Ornitz]

Chris van Lint, <thai1@netvigator.com>, is looking for 
replacement tunnel diodes for his Tek 284 pulse generator.

Sadly, tunnel [Esaki] diodes are almost "unobtainium" these 
days.  Some of the microwave semiconductor manufacturers still 
make back diodes, which are tunnel diodes that have been 
optimized for reverse conduction, and used as sensitive 
detectors.  These have not ben optimized for negative 
resistance and will probably not work in this application.  
Alpha Semiconductor was one of these manufacturers.

At one time Custom Components of Linden, NJ, was the only 
manufacturer of replacement tunnel diodes in the USA.  They 
essentially duplicated the General Electric line of tunnel 
diodes such as the TD-2 and 1N3712.  I have heard recently 
that they no longer supply gallium arsenide diodes.  
Supposedly Metelics Corporation of Sunnyvale, CA, also 
manufactures tunnel diodes.

The company I have heard most about lately is American 
Microsemiconductor, Inc. who specialize in obsolete 
semiconductor devices.  About two and a half years ago, I 
received literature from them on a line of tunnel diodes they 
were planning to produce.  Price was through the roof!

Other possibilities for you to try are Deane Kidd in 
Beaverton, Oregon, a retired Tek employee who stocks many 
replacement parts, and Stan Griffiths, who specializes in 
older Tek oscilloscopes.  I do not have addresses handy for 
either of these gentlemen, but I am sure others here can 
provide these.  I know both of these fine individuals; they 
are really extremely valuable assets for restorers of older 
test equipment - and exceptionally helpful.

If the 21 mA Chris specified is the peak point current for the 
diode, my guess as to type would be 1N3720, 1N3721, TD-5, or 
TD-5A as these have peak point currenys of 22 mA.  Their case 
size is similar to what Chris describes too.

I note Chris' email address lists NETVIGATOR.COM.  This seems 
to be the only Internet provider in the Peoples Republic of 
China that I do not get tons of SPAM from!  If you need to 
email me directly, Chris, please include something in the 
subject line about tunnel diodes or my filtering software will 
reject the email as spam.

        Barry L. Ornitz, Ph.D.     WA4VZQ          ornitz@tricon.net