Dave,
I've had a search through the CDPC (Common Design Parts Catalog) for the tunnel diodes (Tek PN 151-0386-00) in the 465. The service manual says that they are selected from 1N3718, but the Tek part number is not listed as a selected part (as with transistors, whose part number appears to change from 151- to 156- when selected by Tek internal processes, it looks like diodes change part number from 152- to 153- after selection, but I'm just inferring this from what's listed in the Matched or Selected diodes table on page 12-6 of the CDPC). The CDPC also indicates a different vendor part number, STD927 rather than 1N3718, so I don't know what's up with that.
The specs given for STD927 are a 10 mA part with 25 pF capacitance, which appear (based on the Russian Tunnel Diodes list on TekWiki, ) to be matches to 3I306M, 3I306N, 3I306S, 1I305A, 1I305B, 1I308V, 1I308G, 1I308J, 1I308K, 1I308I, 1I308E, or 1I308D (where the rated current meets or exceeds 10 mA and the capacitance is around or less than 25 pF). Most of those are available on eBay.
I also looked for the Tek PN on eBay and Amazon with no success.
-- Jeff Dutky
