[Hammarlund] hq 145a tone chirp/blip when tapping on the table. normal?

[Fernan Bolando]

thanks again to all

i was planning to refresh my stock of parts for my other projects and was thinking
i should also buy a few spare parts for my hammarlund. i was thinking the following

1pc 6BE6
1pc 6C4
1pc 12AX7
1pc OB2

are there other parts i should also include?

regards
fernan ve4feb

> Sent: Friday, November 08, 2019 at 1:27 PM
> From: "Bill Cromwell" <wrcromwell at gmail.com>
> To: hammarlund at mailman.qth.net
> Subject: Re: [Hammarlund] hq 145a tone chirp/blip when tapping on the table. normal?
>
> Hi,
> 
> When my HQ145X was acting badly (when I acquired it) I checked all the 
> tubes. They all checked very good. But the rascal 6C4 was NOT so good 
> and all the "artifacts" including microphonics and gross drift problems 
> disappeared when I subbed another 6C4. Thereafter it was a really good 
> radio and I relied on it when my "pretty" radio went down for repairs.
> 
> On 11/8/19 1:23 PM, Richard Knoppow wrote:
> >     Probably microphonics. Can come from the oscillator tube or just 
> > physical vibration of the tuning condenser or anything else in the 
> > oscillator circuits. Most, if not all, receivers using conventional 
> > variable capacitors for varying the oscillator frequency suffer from 
> > some microphonics. The oscillator tubes can also cause it, particularly 
> > the popular 6C4. There is actually a special low microphonic version of 
> > this tube, can't remember the type number.
> >      You may be able to localize the source by tapping around with the 
> > eraser end of a pencil. Some receivers are much more microphonic than 
> > others, I don't know how the 145 is for this. My HQ-129-X is not too 
> > bad. My R-388 (51J-3) is pretty much free of microphonics but does not 
> > use a variable capacitor for tuning.
> > 
> > On 11/8/2019 9:23 AM, Fernan Bolando wrote:
> >> Hi all
> >>
> >> me again. ive noticed something new :)
> >>
> >> when i listen to a steady cw tone/signal and a relatively strong tap 
> >> on the table
> >> will cause the the tone to chirp or blip. it does not drift though, 
> >> just a
> >> sudden blip blip thing. i just wanted to know if its normally for the old
> >> tech.
> >>
> >> stability seem good after warm up. i can zero beat on a cw tone, just 
> >> fine.
> >>
> >> regards
> >> fernan ve4feb
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> 
> -- 
> bark less - wag more
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