[ARC5] ARC5 Digest, Vol 228, Issue 37

Sun Jan 8 14:49:26 EST 2023

 I think Dell had a big problem with bad motherboard capacitors from China.
Jim 
    On Sunday, January 8, 2023, 02:17:07 PM EST, arc5-request at mailman.qth.net <arc5-request at mailman.qth.net> wrote:  

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Today's Topics:

  1. Re: How Edwin Armstrong invented the superhet (William Cromwell)
  2. Re: [Milsurplus] Duracell Coppertop batteries and other
      things (mstangelo at comcast.net)

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Message: 1
Date: Sun, 8 Jan 2023 13:37:51 -0500
From: William Cromwell <wrcromwell at gmail.com>
To: arc5 at mailman.qth.net
Subject: Re: [ARC5] How Edwin Armstrong invented the superhet
Message-ID: <e3266e4e-ca87-0f52-8902-988def43e56f at gmail.com>
Content-Type: text/plain; charset=UTF-8; format=flowed

Hi,

The Knight Star Roamer used the regenerative IF trick primarily to serve 
as the BFO. It was controlled from the front panel and it did affect the 
bandwidth and rf gain. It was not very satisfactory but was *cheap*. I 
used one for a couple of years.

73,

Bill KU8H

bark less - wag more

On 1/8/23 02:33, 1oldlens1 wrote:
> A comment. A regeneration has two advantages for CW: the first is that 
> as it approaches oscillation it becomes narrower in selectivity.? When 
> it begins to oscillate the oscillation acts as a BFO
> ? There is a critical adjustment just at the point of oscillation 
> where the bandwidth is minimum
> ? ?More feedback will begin to broaden it out more.? ?At minimum 
> feedback the gain is minimum and bandwidth maximum.? Note that the 
> change in gain and bandwidth is confined to the regenerative stage.? 
> Pre selector stages are nor affected.? I don't remember the theory but 
> the change in gain with feedback is probably not linear.? In any case 
> old RDF sets are likely TRF. I believe I have schematics for both 
> Kolster and Radiomarine RDF receivers in some very old books.? The 
> main thing is to be able to here the variation in signal strength as 
> the antenna is rotated. Precision measurement is not necessary, only 
> thr relative variation with direction.? Actually only the null is of 
> interest.
> ? ?There were schemes of adding regeneration to an IF stage to make it 
> narrower and to make it oscillate so as to act as a BFO .? The 
> relatively crude circuit used in the S-38B and later,and SW-54 are 
> examples.? This arrangement is strictly an economy.? The original S-38 
> has one more tube than the later versions.
>
>
>
> Sent from my Galaxy
>
>
>
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Message: 2
Date: Sun, 8 Jan 2023 14:16:45 -0500 (EST)
From: mstangelo at comcast.net
To: "Kenneth G. Gordon" <kgordon2006 at frontier.com>,
    arc5 at mailman.qth.net
Subject: Re: [ARC5] [Milsurplus] Duracell Coppertop batteries and
    other things
Message-ID: <1358984327.947976.1673205405477 at connect.xfinity.com>
Content-Type: text/plain; charset=UTF-8

I remember the era.

I bought some name brand electrolytics from Digi-Key. Years later I received a notice about a class action suit against the manufacturer with instructions on how to join the lawsuit. I didn't have any issues with the caps and just spent a couple of dollars so I didn't bother to replay.

I wondered what happened to that lawsuit? If I find the notice I may follow up.

Mike N2MS

> On 01/08/2023 1:15 PM Kenneth G. Gordon <kgordon2006 at frontier.com> wrote:
> 
>  

> > 
> > --Tom
> 
> I don't know if anyone or everyone here remembers the HUGE problems we had a number of 
> years ago with small electrolytic capacitors used in computers and peripherals, but it was 
> REALLY horrendous!
> 
> Some chinese fellow worked for awhile at a well-known Japanese manufacturer of 
> electrolytic capacitors, and stole their proprietory forumla for the electrolyte.....except that he 
> didn't get the entire formula.
> 
> Then he quit, went back to china, and somehow convinced chinese manufacturers to use his 
> stolen formula to make tens of millions of those small electrolytic caps used on computer 
> motherboards, peripherals, and power supplies, and since they were cheaper than the better 
> ones made in Japan, convinced even "high-end" makers of motherboards, like IBM (before 
> they sold their computer division to china) to install them in almost everything 
> computer-related made in the U.S.A.
> 
> VERY shortly after those things were built, the chinese capacitors failed, some 
> catastrophically, others a bit more slowly, and caused a HUGE problem with defective 
> motherboards, etc. 
> 
> We compiuter techs had considerable difficulty for some time keeping up with replacing 
> motherboards, and other crap.
> 
> Some few of us learned quite early on what to look for and how to replace the caps.
> 
> Although I was wary of chinese-made stuff before this, I have never trusted anything made in 
> china since then.
> 
> Ken W7EKB

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End of ARC5 Digest, Vol 228, Issue 37
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