HQ-170 Audio Hum

[n1arr]

I have an HQ-170 that hums terribly, I have been told that it is at least 1 section of the 4 section can cap.  c82. Has anyone had a similar problem? Can a 4 sect.  be obtained or is it best to substitute 1 to 4  separate  capacitors?   n1arr

[KA1ZGC]

AFAIK, Mallory was the last manufacturer of multi-section electrolytics, and they probably stopped 20 years ago.

The only matching multi-section caps you're going to find that are the correct values will have been pulled from something of equal age, and will probably as bad or worse than what you've got now.

Replacing multi-section caps with individual caps isn't always easy if real estate is at a premium. Fortunately, there's plenty of room in the HQ-170 chassis.

While you're at it, get individual replacement caps for the other three sections, too. If one's gone, the others are going.

My US$0.02.

--Thom
Keep Away One Zorched Ganged Capacitor

[WQ9E]

Thom is correct, there is plenty of room in the HQ-170 to install discrete replacements and do replace all 4 sections.  I know that Tom N0JMY ("hayseed hamfest") has been selling new construction multi unit caps.  Google hayseed hamfest to see his site.  I bought some replacements from him for a couple of radios where there wasn't really room for individual units and his prices are fair and quality is great.

Another weak spot in the HQ-170 is the 6C4 HFO and it is good to have a couple to choose from to select the one that works best (oscillates throughout the range, no tendency to jump frequency).  

To align the HQ-170 properly you MUST use a generator that will go down to 60 Khz.  If your RF generator doesn't go that low your audio generator may go that high.  Before I got the converter for my HP-8640B I used an HP-200 audio oscillator to hit the low frequency Halli and Hammarlund final IF stages.

Although some don't like the audio, the HQ-170 is a very good all mode receiver and really comes into its own under tough conditions.

[w5kcm]

I have had the HQ-170 for several years. Mine also developed a hum a while back and it was one of the power supply electrolytics. I mounted a terminal strip at the base (below the chassis) of the multisection can capacitor and connected several electrolytics to replace the multisection capacitor. This has worked well for several years.

[KA1ZGC]

(Meant to post this yesterday, but work beckoned).

I know that Tom N0JMY ("hayseed hamfest") has been selling new construction multi unit caps.

Neat stuff. Thanks for passing that on!

BTW, it's http://www.hayseedhamfest.com/ for those who didn't bother googling. 

Although some don't like the audio, the HQ-170 is a very good all mode receiver and really comes into its own under tough conditions.

Hear, hear.

I find the HQ-170 is a great battle-mode receiver, far better than my HQ-129X. The filtering is certainly far superior to the 129, and the bandwidth is enough for most AM transmissions.

Granted, for hi-fi signals on a quiet band, it's not the ideal receiver; but when the going gets tough, the 170 pulls 'em out of the slop. I'd like to have one myself.

[W2PFY]

My HQ-170A has a somewhat loud hum. It does not have a grounded type AC plug. I found by reversing the plug in wall socket, the hum went down by 90 percent.

[ke7trp]

http://www.tubesandmore.com/

Has the multi section caps and mounting tabs if you want to keep the radio original or close to it. I am not sure of the volt and value you need. I have the catalog in front of me if you want to list it, I can come up with one that may or may not work. 

I normaly order single caps and mount them on a terminal strip under the radio.

C

[Ed/KB1HYS]

My HQ-170A has a somewhat loud hum. It does not have a grounded type AC plug. I found by reversing the plug in wall socket, the hum went down by 90 percent.

Does that mean that one side (neutral) of the line cord goes to the chassis at some point?

[N3DRB The Derb]

put that radio on a 3 wire grounded plug before you get the shock of your life.

[w4fms]

I second the use of Hayseed.  I needed some cans for a Globe King restoration and they made exactly what I needed..even the smaller size 1in which is hard to find anymore.  Frank

[KA1ZGC]

My HQ-170A has a somewhat loud hum. It does not have a grounded type AC plug. I found by reversing the plug in wall socket, the hum went down by 90 percent.

Does that mean that one side (neutral) of the line cord goes to the chassis at some point?

Reminds me of Old Buzzard George's rigs. He did everything that way, one side of the line cord tied to the chassis, and a two-prong, non-polarized plug on the end.

I think it was Jay who called them "nice knowin' ya" rigs.

Good ol' George. They just don't make 'em like that anymore.

--Thom
King Abraham One Zebraham George Charlie

[WQ9E]

Does that mean that one side (neutral) of the line cord goes to the chassis at some point?

This should not be the case with the HQ-170 but there may be a very leaky line bypass cap or someone has done some interesting clock wiring. 

In any case, the chassis should be connected for proper RF and AC ground.

[ke7trp]

This reminds of my a story about getting shocked.  I purchased a D104 at a hamfest. It came with the Two prong plug on it. I plugged it into my Transmitter.  Warmed it up and when I grapped the Mic to key it, I got the shock of my life.  It took me to my knees..

Some idiot had CUT the Shield off the inside and wired the PTT to Ground. So the entire body had full voltage on it.  We studied the thing and decided, That the guy did it on purpose hopping to shock someone. There would never be a reason to wire it this way. 

Always check things out!  I use the old repairman trick of holding the neg terminal of a meter in your hand and touching the Red to the case,  BEFORE I work on something.  If line voltage is on that case, You will see it on the meter and you wont get shocked.

C

[W2PFY]

Does that mean that one side (neutral) of the line cord goes to the chassis at some point?

No, one side does not go to ground. It's a trick I learned long ago that sometimes reversing the plug will cut down on hum. I will put a new three wire plug on it before operating season starts again for me. It's just a lazy way around it. There are probably caps to ground on both sides of the AC input that leak. With my receiver, you need to be careful when changing out a coax with the plug in the socket. It measures about 60 volts AC from the coax to ground. Attached is a picture of my good friend Dirk showing what can happen when you do not ground your HQ-170    

[n1arr]

Thanks to all for the help, advice and in some cases helpful humor. Also for taking the time to reply and include links.  n1arr