[HBR] Help with old home-brew receiver

[hbr@mailman.qth.net]

Jim said:
> It IS possible to reverse-engineer a homebrew rx like this.

And very interesting to us homebrew receiver vultures!   Kevin, I hope 
you're not feeling you've gotten just a bit too enthusiastic a 'welcome' 
to the list!

Even if you just trace out the control grid and plate connections on 
each stage -- what other stages does each stage connect to -- you'll 
have the big picture.   And that's enough to get started making it 
work.   The use of those recycled command set caps is ... searching 
for suitably delicate word ... unfortunate.   You will very likely have to 
replace all of them, right at the start;  I'm not sure I've ever gotten a 
command set working without changing at least one and they get 
worse as the years go by.   If you want to keep it authentic, contact 
me off-list and I'll see about liberating some ARC type 12 caps;  
they're structurally identical but infinitely better quality.   Not quite 
identical, I guess -- the insulating top is plastic or ceramic, rather 
than mica -- but same 'tub' structure, mounting method, same type 
terminals.   

Don't just throw the juice to it, as a shorted cap will probably take out 
at least one other part.   Also, they do not all fail right away ... some 
will go from 'works but slightly leaky' to 'dead short' over a period 
ranging up to weeks of operation.   Been there, done that ...

The design is interesting.   Either the ?? tube is another mixer and 
it's a double conversion receiver without an RF stage, or it's an RF 
stage and it's single conversion.   Is there another IF transformer?  
How many coils per band?

I can't recall a published design going either way, but it could be a 
modification of one.   Okay, so I'm just a sucker for this stuff -- I'll 
take a look at my QST microfishes and see what I can find.

Welcome to the list!

Walt Hutchens
KJ4KV