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Author Topic: Hammarlund HQ-170A  (Read 528 times)

AE9DX

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Hammarlund HQ-170A
« on: November 26, 2021, 02:24:38 PM »

I have a Hammarlund HQ-170A that was working fine until one day it just wasn't. It just seems like it's lost it's receive ability. I've been through the tubes with my B&K 606 and even replaced the the HF oscillator, mixers, prod. detector tubes, etc. There's plenty of audio present, just no signal. Any advice will be appreciated. Is there a way to test the IF cans, without opening them up? I don't want to mess with the film caps unless there's no other option. Thanks, john, AE9DX
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N2LXM

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Re: Hammarlund HQ-170A
« Reply #1 on: November 26, 2021, 03:20:54 PM »

The first thing, get a schematic. Do a resistive and voltage checks, clean all controls and switches.  Then try injecting a signal starting with the first audio and then work back through the IF stages. A simple muliti-vibrator style injector will work. This will hopefully get you to the stage that's the problem. 
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W8RMV

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Re: Hammarlund HQ-170A
« Reply #2 on: November 26, 2021, 03:32:56 PM »

My 180 does that also.  It was the band switch for mine.  I have to clean it once & awhile.
The durapaper caps should be replaced ASAP.  I put films in.  Leaky caps can be hard on tubes.
Good luck - Bob
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K1VSK

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Re: Hammarlund HQ-170A
« Reply #3 on: November 26, 2021, 03:35:16 PM »

Another band switch vote. That happens to mind periodically and is a likely cause
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AE9DX

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Re: Hammarlund HQ-170A
« Reply #4 on: November 26, 2021, 04:33:19 PM »

Thanks to all who replied. I guess great minds do think alike! Hi!
The band switch will be my first place to go, then replacing caps and doing voltage checks again. Something I probably should have done earlier when I replaced the filter cap!
That radio and one of my Drakes are my "winter projects"
73!
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KM1H

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Re: Hammarlund HQ-170A
« Reply #5 on: November 28, 2021, 12:51:11 PM »

My 180 does that also.  It was the band switch for mine.  I have to clean it once & awhile.
The durapaper caps should be replaced ASAP.  I put films in.  Leaky caps can be hard on tubes.
Good luck - Bob

The 180A was produced during the years of disc ceramic, paper and Mylar (film) caps in .01 to .1
 and higher as technology was rapidly changing and I would suggest determining which ones before doing a wholesale swap.

Another source of no signal is a defective Centralab Couplate in the audio which was common to both versions.

These were also the years of Silver Mica Disease in IF cans that could also cause open coil windings.

Carl
National Radio 1963-69 and most all makes repairs up to present.
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