[Boatanchors] Collins Filter Adaptor

[Ulrich N Fierz]

Hi alllooking at the modified circuit I was reminded of the one risk that is inherent in these adaptors: should the tube V1 fail or another effect cause B+ to be loaded at the plate end excessively, the current will pass through the filter primary and likely cause sudden failure of the coil and thus the entire filter. 

To avoid this I inserted a plate choke and coupling capacitor to my Collins 51J-4 adaptor unit. The idea was based on comments a few years ago and it appears IMHO to make sense. I've also applied it to my Collins HF-8054 IF-cards where the transistor current originally passes through the filter. The coils were made using ferrite pot cores (with air gap).
Wish you good luck with your projects!73,Ulrich  hb9aik - vk6bqd Ulrich N Fierz
Telecommunication Engineering Services
Zurichbergstrasse 203
CH-8044 Zurich
Switzerland
<hb9aik at yahoo.com>