The AM Forum

Hi all. I have a Hammarlund HQ-170. Receive on 160 & 80 is great.
40 thru 10 not so great. re-tubed and no help. Frequency alignment is
right on just low sensitivity. Any suggestions would be helpful.

I would start by checking and/or replacing V3 and the voltages on the pins of V3. Also, check the components associated with V3. Also check transformers T2 and T3.

Make sure the band switch is not intermittent. Long switches, as used in many Hammarlund high quality receivers, have a certain amount of "play" between the control shaft and individual wiper wipers. That's especially true at the rear of the Rx where the input RF circuits are loca6ed and switched. In addition to checking play in the switch, it won't hurt to use a good contact cleaner on the switch but do not flood the wafers when doing that. Try "teasing" the band switch while listening to a signal on a poorly-performing band to notice if level suddenly pops up or disappears.

Verify tube dc voltages at their sockets and visually check signal wiring by following buss wire leads from band switch to tube pins or associated components near tube sockets. If visibility is limited in following that wiring use an ohmmeter to check circuits from coils (on low gain bands) to tube sockets/nearby components.

Good luck and Happy Fourth!

Bob - NE
 

The only thing that changes when going from dual to triple conversion is that the front side of the SW-2F wafer shorts the upper 455KC winding of T1, and enables  the lower 3035KC winding, while the rear side of the wafer turns the 2580KC oscillator portion of the V3 circuitry on or off by shorting L8.  

Everything else is "in circuit" regardless of selected band.  If I were to hazard a guess, my first thought would be that the upper winding of T1 isn't being shorted when in triple conversion mode, or something in the 455kc coupling network is amiss, maybe the caps (mica?) in one of the cans.   I've heard these can sometimes be problematic.

Of course the oscillator components are suspect as well.

I'm no HQ expert by any means, I just happen to have finished refurbishing (http://s670.photobucket.com/user/mikeinkcmo/library/Radios/HQ-170?sort=9&page=1) my "new" 170 a couple days ago, so this stuff is fresh in my mind(?).

Great restoration job Mike!

Joe-W3GMS

THanks Joe, fun little project.

The IF cans on a 170 have SM caps if memory serves.  They can be a liability, as silver will actually diffuse into the mica over time.

I have never rebuilt a can.  Please know that K7PP has many Hammarlund videos on YouTube.  You might get some ideas from these videos.  You might also contact him directly.

Good luck!

Matt