HQ 170 AM audio question

[WV9R]

I recently picked up a very clean HQ-170, now I've heard the AM audio isnt the best, but this one is terrible. If I try to listen with the selectivity set to 3kcs and both sidebands the audio is muddy and distorted, but if I narrow it down to the 2kcs setting it gets better, still a bit muddy but better. I've checked all of the tubes, made sure all of the pins are clean and making good connection, and looked at all of the obvious, to me anyways obvious things. But I am missing something, does anyone here have any ideas or have had this problem before, or for a last resort can anyone give me a name of a good repair facility for this vintage, I'd like to end up with a little hair left on my head, been pulling it out a bit. Like I said if i narrow it down to the 2kcs setting the audio is almost liveable, listened to a nice group on 1.885 the last couple of nights, if I tune a bit off the audio brightens up and is clearer, otherwise way too much bass and muddy sounding. any help will be appreciated.

[WQ9E]

The HQ-170 (and its 180 sister) aren't high fidelity on AM but working properly they sound fine and are excellent when you need to fight QRM and QRN; when I was using an HRO-50 with my Desk KW this is (my HQ-170A) one of the receivers I would patch in when I was net control for the MidWest Classic Radio Net.

If it isn't something simple (like the slot filter being engaged when you don't want it), then a previous owner may well have tried to align it without really understanding how to do it properly or having the necessary equipment.  The final 60 Kc IF is very critical in its adjustment and most RF signal generators don't go that low.  I use my HP "audio" oscillator which also goes up to 200 Khz. 

If the audio is otherwise OK on CW/SSB and the intelligibility is improved by "mistuning" on AM then improper alignment is most likely your issue.  It isn't difficult if you are careful and have access to a good signal source at 60 Khz. and a frequency counter to set it properly.

73, Rodger WQ9E

[w5rkl]

I had this same problem with two HQ-170's. I simply adjusted the 60Khz IF cans until the audio sounded better with the SIDE BAND switch in "BOTH" and the SELECT KCS switch in "3".

If you are not sure which cans are the 60Khz IF cans, look at the top of the chassis. Along the right side of the chassis starting from the rear, you will see two cans close together then a tube, then two cans close together, then a tube, and finally two cans close together. These are the six 60Khz IF cans. Adjust only these cans!! Do not adjust any other can.

Adjust the cans individually, a little at a time, until the audio improves.

73
Mike
W5RKL

[w5rkl]

My method of improving the audio in the 170 by mal adjusting the 60Khz IF cans may not be what others do but it is a method I found that worked for me without significantly reducing the 170's gain. Also this method has not significantly changed the "U" and "L" sideband settings. Whether you choose to adjust the 60Khz IF can or not is your decision. I will say, if you adjust the 60Khz IF cans and the gain is significantly reduced you will need a stable 60Khz signal generator to readjust them back to where they should be. I use a URM-25D which has a 60Khz output. Most inexpensive ham signal generators such as the Heathkit and Eico generators don't go below 100Khz. Although the URM-25D is a stable generator, I connected a frequency counter to the generator to ensure the signal remains within a Hz or two when aligning the 60Khz IF by following the instructions in the HQ-170 manual.

The manual for the 170 can be downloaded from the bama website and it contains the IF alignment instructions plus pictures of the various RF, IF, and oscillator can locations on the chassis.

73
Mike
W5RKL