HQ-170A Problem--Need Help!

[WB3BIQ]

Hello all,

I could really use some help/advice on a recent receiver problem and would love to borrow on the members' expertise. Here it is:

I bought my HQ-170A on Ebay auction six months ago on Ebay auction and it has worked well (except for the notch/slot controls) on all bands until two days ago.

I operate mostly on 40 Meter CW and until two days ago I could receive fine. Suddenly, the signals all disappeared, but I still had volume.

Switching the bandswitch, I could hear signals well on 160 meters and 80 meters, but that's all! (I understand that these two bands are processed by the receiver's "dual conversion" system: the higher bands are processed by "triple conversion," so therein must lie my problem.

Using my reliable tube tester I tested ALL the tubes and they all checked out okay. Removing each tube to test, I also sprayed contact cleaner into the tube socket to eliminate that problem. Didn't help. Looking under the chassis, I could see no apparent component failure.

Do you have any suggestions on where I might next look to try to solve this problem?

Thanks in advance for any and all help you might be able to give.

73's, Rick, W B 3 B I Q

[N2DTS]

I only know what the receiver looks like, but it sounds like a band switch problem, or a dirty xtal socket if it uses them in one of the converters.

A careful inspection of all the band switch contacts dealing with 40 meters might show something.

I guess you can rule out the audio stages, the detector stuff, power supply stuff, and some of the IF stages, so you got mixer/converters, antenna tuning....

Brett

[Ed/KB1HYS]

I have a manual in PDF format, I emailed it.

The only stage that effects all the higher bands but not the two lower would be the third mixer. You'll have to poke around and make sure the mixer is getting the oscillator signal applied.

take it piece by piece and apply basic trouble shooting approach. trace the signal through the set. Take your time. Since two of the bands are working ok, (double conversion) it looks like its the third mixer stage having a problem since its the only stage that effects all the higher bands but not the two lower.  You'll have to poke around and make sure the mixer is getting the oscillator signal applied

A scope and a multimeter should get her done.

[WQ9E]

Rick,

It sounds like a problem with V-3 or perhaps the 2.58 Mhz. crystal.  If you have another 6BE6 try substituting (a tube checker is far from infallible) or otherwise try interchanging V-3 and V-5 (they are both 6BE6 tubes) to see what happens.  If you have a functional general coverage receiver, put an antenna lead from it near V-3 and tune it around 2.58 Mhz. to see whether the conversion oscillator is running when you have it on the higher bands.

V-3 operates as a 455 khz. IF amp for 160 and 80 and as a crystal excited mixer for the higher bands. 
A poor 6BE6 may work OK as an IF amplifier but not as an oscillator/mixer.

Rodger WQ9E

[The Slab Bacon]

I had the same problem with mine, and I have run into it as well with other "gray faced" Hammarlunds that I have repaired.

Swap out the 6C4 first conversion L.O. tube, It is probably not always oscilating.
Just because it tests good on a tube checker doesnt mean it will work in that circuit. I have had brand new ones that wouldnt oscilate   It seems to also only happen on certain bands. My 170 was dead on 160, go figger.

I have ever bothered to investigate further why this anomoly happens, but it's usually 1 or 2 bands that are affected, all the other ones work OK. You may have to "test / select" the tue that works best (new or used).

                                                   The Slab bacon