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Author Topic: HQ-160 suddenly quiet  (Read 8800 times)
AC5UP
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Posts: 3875




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« Reply #15 on: September 16, 2012, 12:19:54 PM »

...but they sure don't look too good.

I have a hunch that's a textbook example of silver migration as mentioned earlier. Silver oxide is conductive. But what I'm seeing doesn't exactly fit with the 'sudden death' scenario you described. More typical of an IF can going bad is a radio that plays for a while, goes deaf, might come back for a few moments, goes deaf again, or might develop random crackling for no obvious reason.

Regardless, I'd leave the mica sheets out and decide how best to replace them with a pair of modern silver mica condensers. Typical value for those would be 100 to 120 mikemike. You want a stable part with less emphasis on the tolerance as you'll align the can to whatever value the new condensers might be. Then hope they stay that way for a long time...
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K7WXK
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Posts: 68




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« Reply #16 on: September 16, 2012, 01:57:25 PM »

...but they sure don't look too good.

I have a hunch that's a textbook example of silver migration as mentioned earlier. Silver oxide is conductive. But what I'm seeing doesn't exactly fit with the 'sudden death' scenario you described. More typical of an IF can going bad is a radio that plays for a while, goes deaf, might come back for a few moments, goes deaf again, or might develop random crackling for no obvious reason.

Regardless, I'd leave the mica sheets out and decide how best to replace them with a pair of modern silver mica condensers. Typical value for those would be 100 to 120 mikemike. You want a stable part with less emphasis on the tolerance as you'll align the can to whatever value the new condensers might be. Then hope they stay that way for a long time...

I believe that may be what happened.  As I recall, the radio didn't work at first, but then mysteriously came to life and worked fine for several days.  Then it went quiet again and stayed that way to date.  Anyway, from what I can diagnose, this IF can needs attention.  I am cautiously optimistic.

The replacement values for the caps are 330uuf.  Should be no problem finding ones that will fit comfortably inside.


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W9GB
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Posts: 2623




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« Reply #17 on: September 16, 2012, 02:18:48 PM »

I am glad those Antique Radio forum photos helped (picture says a thousand words).

Good photo of a classic silver migration issue for your HQ-160 (see the dark, black areas).
Some have successfully used silver cleaners (then reinstall),
 while others just replace with standard 500 V silver mica capacitor in their place.

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K7WXK
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Posts: 68




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« Reply #18 on: September 18, 2012, 06:12:25 AM »

Well, inspite of all your suggestions and a very carefully repaired IF can, the problem still exists.  This one has me scratching my head.  I know it is something simple, for the radio worked and then suddenly it didn't.  I just need to take a breath and start over.  As one of you said, do the research.  I know that the signal still stops at the output side of T-3.  That will be the focus of my toubleshooting until I can eliminate that as a probable cause.

I'll let you know how it goes.

Marc
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K8AXW
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« Reply #19 on: September 18, 2012, 09:48:28 AM »

Two reasons why the signal stops at T3.  1-T3 is bad.  Since that has been "repaired" then. 2- Something on the output of T3 is pulling the signal (which will probably be weaker than the input signal level) down, like to ground.

Lift the output of T3 and see if the signal shows up on the scope.  If it does, then go into the next stage and look for something wrong.
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W9GB
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« Reply #20 on: September 19, 2012, 02:18:56 PM »

You are positive you did not have a broken wire on T3 ??
Did you perform standard DC continuity checks ?

Do you have access to a GDO ?
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K6CRC
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Posts: 47




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« Reply #21 on: September 19, 2012, 07:15:44 PM »

May have been mentioned. I notice the alignment caps sometimes are intermittent.  I did an alignment of an HQ-180, and had a similar 'where did the signal go?" moment. I shot the variable caps with DeOx, then *carefully* wiggled with a small screwdriver (don't turn or you will need to align). Put on power, and it worked.

The IF trannies are very sensitive, and extremely easy to break.

160 is my favorite boatanchor.   

Good luck.
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K7WXK
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Posts: 68




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« Reply #22 on: September 19, 2012, 08:31:59 PM »

GB,

I only have the vtvm for continuity checks and all was good.  I suppose I could have missed something.  The scope goes flat line at the output of T-3, so I'm going to focus on it again.  What else should I be looking for?

CRC,

What caps are you referring to?  The only variables (trimmers) that I know of are on the RF coils and oscillator coils (other than the main tuning, BFO, and ant trim).  Since you are familiar with the HQ-160, any bits of knowledge would be greatly appreciated.  This thing has really got me.  But it sounds very similar to what you described on the HQ-180.  I began a routine alignment by starting with T-3 thru T-7 and was noting that adjusting the cans had no effect on the signal (which I was monitoring using the vtvm).  It was during the troubleshooting that I hooked up the O-scope and discovered no signal past T-3.  I haven't touched the RF or Osc tuning, yet.
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K7WXK
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Posts: 68




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« Reply #23 on: September 21, 2012, 07:05:27 AM »

Thanks to everyone who has contributed his/her thoughts and ideas.  I have also posted on Antique Radio.com to get max exposure.  As one might expect the recommendations are very similar to the ones here.  I keep arriving at the T-3 transformer.  So I will need some time to research and re-assemble.  I will post again when I have some substantive results.  In the mean time don't hesitate to post your thoughts regarding this problem.  It is by no means a done deal.

With great appreciation,
Marc
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K7WXK
Member

Posts: 68




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« Reply #24 on: September 21, 2012, 09:50:21 AM »

Somehow, during my troubleshooting I overlooked T-4.  I can't seem to get a signal accross it either.  Perhpas I have a two-fold problem.  I plan on removing both T-3 and T-4 and thoroughly investigating. 

In summary, signal good from audio output through 1st IF amp (6BA6).  This includes all circuits in between.  Also, from antenna through RF amp, mixer, converter to input of T-3.  Roadblock exists between output side of T-4 to input side of T-3.  The Q-mult has been totally isolated during these tests.  I think I am getting closer!

More later.

M
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KL7HNY
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Posts: 5




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« Reply #25 on: September 23, 2012, 03:45:17 AM »

What a great thread, and what great resources we've got in the members here!  I've been reading as much as I can before I start actually start to turn-and-burn inside the Hammarlund trio I recently acquired from eekBay: an HQ-100, -110, and -145.  The -100 worked right out of the box, having been a "daily use" rcvr in the shack of the ham who sold it.  I will put in a TenTec 455 kc BFO kit, because I don't have the patience to use the Q-mult for detecting SSB and CW reliably. 
The -110 has been recapped but needs troubleshooting, and the -145 needs tubes and a re-cap.  But the tips I'm picking up in this thread, along with the links, have already put me on a much better footing than I got way back in the Novice classes I took with my dad (wn4anv, SK) back when I was 9, and now I can re-live my misspent grown-up life in commercial two-way with all its silly solid state gear and wide band devices.
Hollow state rules!
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K7WXK
Member

Posts: 68




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« Reply #26 on: September 23, 2012, 07:20:25 AM »

HNY,

You may have to follow this thread for a while to get to the finish line.  I am awaiting parts for the IF cans that are suspect.  Of the radios you have acquired, I have owned both the 110 and the 145.  Got the 110 back in the 60's and for me was a quantum leap forward.  Little did I know that it was basically an entry level radio similar to the 100.  The 145 is a bit more sophisticated, and quite a nice rig, not too different from the 160.  I like Hammarlunds because they look cool, and, until I encountered the problem with the 160, are relatively easy to work on.

By the way, the contributors here are just a tremendous source of information and experience. 

Enjoy,
Marc
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K7WXK
Member

Posts: 68




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« Reply #27 on: October 07, 2012, 07:56:52 PM »

The receiver is FIXED!  It turned out to be T-2, even though signals were passing through it and very little was passing through T-3.  The silver mica disease is bad in all the IF's, so I will be changing the caps in all of them, but for now the reciever is working very well.

Thanks for all your help with this tough challenge.  If I knew a little more about the Oscilloscope I probably could have nailed it down a lot sooner, but I have learned a ton just on this radio alone.

Your tips, links, pics, etc. have proved invaluable.

Forever indebted,
Marc
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