[Hammarlund] Possible mods - HQ-110

Kenneth G. Gordon kgordon2006 at frontier.com
Sat Jul 9 13:16:33 EDT 2011


After reviewing the circuit diagram of my HQ-110C, I have arrived at 
the following tentative mods.

1) Replace V6 6AZ8 2nd IF tube socket with 7 pin socket, or build 
9pin to 7pin adapter.

2) Rewire 2nd IF stage to straight 6BA6 IF stage as nearly identical 
with 1st IF stage as practicable. This eliminates that marginally 
working "power detector" (and BFO) for CW/SSB and provides the same 
level of IF selectivity for CW/SSB as for AM, yet retains the 
original "S" meter functionality, adding its usefullness for CW/SSB.

3) Eliminate 6BJ7 triple-diode, replacing with solid-state diodes, 
possibly hot-carrier diodes, mounted on terminal strips. This retains 
all original functions, including AM detection and both original AGC 
circuits, yet provides a "free" socket for the next mod.

4) Rewire 6BJ7 socket for a high-transconductance dual triode (6ES8?, 
12AT7?) for a) BFO, and b) triode product detector. One effect of 
doing this is that it separates the BFO from being in such close 
proximity to the 2nd IF (originally in the same tube and tube 
socket), and should reduce or eliminate the BFO signal from effecting 
the AGC circuit, which was the main reason one could not use AGC or 
the "S" meter when in CW/SSB mode.

5) Rewire mode switch to receive CW/SSB audio from PD (this is a very 
simple change, requiring the re-routing of one wire).

6) Adjust time constants of AGC circuitry for "fast" and "slow", 
possibly using the "MAN/AVC" switch. This prevents having to drill a 
new hole and mount a new switch.

These mods should provide no external changes, and require no new 
socket holes, but should make what I consider to be a fairly decent 
receiver into a better performer for CW/SSB.

Your thoughts?

Ken W7EKB


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