[Hammarlund] HQ-160 Work

[Patrick]

Byron:

If you took good notes and photos and you are really happy with the 
result, you should consider writing this up for Electric Radio. I'd 
enjoy reading about it even though I might personally choose to leave my 
radio's near original.

Pat
wa4tuk



On 9/20/2011 11:44 PM, Byron Tatum wrote:
> Hello-
>      Just a report to fellow Hammarlund enthusiasts about some work I did to an
> HQ-160. I hope I do not offend any purists as holes were drilled and punched. I
> believe the receiver is quite a bit more usable, however.
>      1. I reworked the 6BE6 converter by removeing the little subchassis
> containing the 6BE6 and T-2. Took out a couple of capacitors and the 3490 KC
> crystal. Rewired it as a straight mixer, the same as the first mixer, with a
> sub-mini teflon coax bringing in LO signal. Replaced the module in receiver.
> Removed the coax cable that went from 6BE6 screens to bandswitch (this
> originally turned on / off the 3490 KC osc section of 6BE6).
>      2. Installed a 6BH6 3490 KC crystal osc over near canned electrolytic cap.
> Used a 150K screen dropping resistor. Turning the osc on/off by grounding the
> screen pin of 6BH6 using bandswitch contacts that were freed up previously. Put
> a 270 ohm resistor in series with this grounding lead. The 3490 osc
> is activatedon on the upper two bands. The performance on upper two bands in
> improved some by this conversion to a mixer, with separate osc.
>      3. Installed a 6BH6 tube toward very front of chassis, adjacent to BFO coil,
> inline with 6AQ5 and 12AX7. Placed a small, square tinplate box around tube
> socket on chassis underside, to shield the tube socket wiring from 12AX7 Q-Mult
> tube wiring. Used feedthru caps and submini teflon coax, wired this up as the
> new BFO osc. using original BFO tued circuit.
>      4. Stripped the parts from 6U8 "BFO / linear detector" tube socket. Re-wired
> this as a 12AU7A twin-triode product detector, very similiar to version in
> Collins 75A4 receiver. Fed IF signal to one triode grid, the BFO to the other
> triode grid.
>      5. I am in process of replacing the "AVC / MAN / CW" switch with one where I
> can operate AVC with the BFO on. I have already operated the receiver in this
> fashion by disconecting the two AVC lines that are grounded by switch when the
> BFO is turned on. The new product detector really sounds good with AVC. I
> experimented with some mylar caps increasing the release time on the IF AVC
> line. Also, I jumpered the S-Meter connections that are opened up when BFO is
> turned on allowing S-Meter action using product detector. I was very glad there
> is no detectable BFO leakage into the IF.
>      6. Removed the tube rectifier and socket, converted power supply to solid
> state and installed a nice hermetically sealed choke over tube socket hole,
> making supply choke input.
>      7. Replaced some of the "couplet" modules with discrete components.
>              OK, I guess enough description of my butchery here. But, I have
> heard people inquire about having AVC with product detector use, and with the
> original detector that would probably not worked well as both IF and BFO were
> fed to same grid on the pentode section of 6U8. Since I had broken up the 6BE6
> converter (second mixer) on a HQ-170 and HQ-180, and liked the results, I wanted
> to try it on this HQ-160.
>                                                                      Thanks,
> Byron WA5THJ
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