Tektronix Oscilliscope 485 Trigger Tunnel Diodes

[Gbar]

Tunnel diode Tektronix part numbers : 152-0177-02 and 152-0177-00
Does anyone know where I can source the above TD's or know of equivalents I could use ?

[EggertEnjoyer123]

You can buy USSR tunnel diodes on fleabay. Look at the tek wiki for more information

[tggzzz]

First question: are you sure you need new TDs? There can be other faults in the trigger circuit!

Second question: where have you looked? The TekScopes group/forum has a lot of info and the denizens are very knowledgeable.

[Wallace Gasiewicz]

I did not look at his list but this guy has lots of HP and Teck parts:
https://www.eevblog.com/forum/buysellwanted/fs-new-test-equipment-repair-parts-hp-agilent-tektronix-fluke-etc/msg1238752/#msg1238752

[Gbar]

Hi, thanks for your reply.
The tunnel diode leads have corroded so much that the TD actually fell off the board. so before I can find faults elsewhere on the trigger board `I have to replace them.

I have searched the internet and the consensus seems to be that these 10MA 2uF ,4uF diodes are obsolete so I was wondering if anyone knows of equivalents.
Regards

[tggzzz]

Hi, thanks for your reply.
The tunnel diode leads have corroded so much that the TD actually fell off the board. so before I can find faults elsewhere on the trigger board `I have to replace them.

I have searched the internet and the consensus seems to be that these 10MA 2uF ,4uF diodes are obsolete so I was wondering if anyone knows of equivalents.
Regards

Ouch! I presume there's no way you could re-attach wires in place of the leads.

It would surprise me if the TDs were the only thing corroded. Does everything else work, e.g. can you display lissajous figures?

[Zenith]

I believe these were selected 10mA tunnel diodes type SMTD998. The usual source for parts like that is an unrepairable similar scope, or plugin, used for parts. In fact if you use a Tek 400 series scope regularly, they are now getting to be so old that it's worth having another as a parts mule.

As said earlier, one of the ebay Russian tunnel diodes might be a suitable substitute. Check with somewhere like https://groups.io/g/Tektronix. Maybe someone else has done this, which might save a lot of experimenting.

If you have a diode with leads so rusted as to fall apart, my guess would be that the scope has been kept somewhere very damp for a long time. There may be so much other damage, it's beyond practical repair.

[Wallace Gasiewicz]

Sphere in Canada is going out of business.  I was just looking thru their website.  They have some Tek Tunnel Diodes that are not a match for your Tek number   
Perhaps they might be usable? I do not know. Maybe someone more knowledgeable here would know. Maybe check it out, this link goes directly to the Tek Parts page with the diodes. 

https://www.sphere.bc.ca/oldsite/test/tek-parts/tekparts5.html

[David Hess]

There is a Russian equivalent, however when I checked several years ago, demand for that particular low capacitance (fast) diode had exhausted the supply.

[Gbar]

Thanks for all the feed back.
The scope basicaly works but fails to trigger.
I have tried resoldering the leads back on but not too successfully 

I will just have to use it as it is until I get a replacement.

Thanks again
Graham