Making a Halli SX-62B from a SX-62A

[AB3FL]

I am trying to add the AFC circuit from the Halli SX-62B to my SX-62A.  The schematic shows a 1n3182 varicap/varactor diode doing the dirtry work.  The NTE replacement is NTE614 which I have.  I have wired everything up exactly as the SX-62B, but it seems to be working as an anti AFC.  It only works on Band 6(52-108MC).  It is fed from the Discriminator which would be at 0 DCV when everything is properly tuned.  When I turn on the AFC, it jumps up or down too far.  Example if I zero the discriminator it will jump to roughly -1.6VDC or +1.6VDC.  It will never lock at zero.  The diode is not backwards.  I have attached the SX-62B skizmatic

thx

Tom - AB3FL

[AB3FL]

I got it working.  Damn discriminator.  Hardest thing to align even with a Heath IG-57A sweep generator and a scope.

Tom - AB3FL

[Edward Cain]

Hi Tom,

   Can you tell us more about what the problem was. I may try this mod on my 62.

Thanks,
Ed

[AB3FL]

What is the nominal voltage swing on the outpooot of the discriminator?

Tom-AB3FL