[Milsurplus] Arc-38A as modified by RCA

[Jim Whartenby]

FrancescoNo issues here about disagreements.  I am here to learn and share what I have discovered.

For whatever reason, I did not make the connection that the suffix "S" stood for "Selected" or "Special"; my bad.  Your comments now make perfect sense.

Raytheon supplied the 5840S subminiature tubes so I doubt that I will find out what "S" actually stood for.   Perhaps it was nothing more then just a microscopic visual inspection?  I know that visual inspections were part of the early process in getting a handle on what was happening to cause the ARC-21 reliability issues.  Debris and broken welds on the inside of the tube envelope were mentioned in the early reliability reports.  So perhaps I will take another look at them to see if there is a mention about the self inspection of tubes at Raytheon.

I have several examples of the ARC-21 here.  None are from the first 1952 contract of 3900 units.  All are from the third contract and have serial numbers in the 4XXX range.  It appears that RCA did not start over at zero when supplying ARC-21's under new contracts.  So I would guess that all of the first contact ARC-21's became ARC-65's.  The ARC-21 to ARC-65 conversion article in the house pub "RCA Engineer" mentioned in passing that about 5000 ARC-21's were converted to ARC-65's in the late 1950's.  The last ARC-21 build was changed to ARC-65 sets.  I don't know if this was the the fifth contract or not.  

>From one of the congressional reports on the ARC-21:Firstproduction contract: AF33(038)-18325, Date: 1952, Quantity built:3900Secondproduction contract: AF33(600)-32331 Date: 1956, Quantity built: 121
Third production contract: AF33(600)-32926 Date: 1956, Quantity built: 380
Forthproduction contract: AF33(600)-33883, Date: 1956, Quantity built:551
Fifth production contract:AF33(600)-35867, Date: 1957. Quantity built: 442
Total built as of 20 April 1961: 5,394I have no idea of how many contracts were let for the ARC-65 or how many were built.


Francesco, when this Covid thing gets resolved, hopefully we will bump into each other again at a Texas Hamfest!

Regards,Jim

I wonder why people argue over the 10% of their differences and ignore the 90% they agree on?

-----Original Message-----
From: frledda at att.net
To: 'Jim Whartenby' <old_radio at aol.com>; Milsurplus at mailman.qth.net
Sent: Mon, Nov 2, 2020 2:27 pm
Subject: RE: [Milsurplus] Arc-38A as modified by RCA

<!--#yiv3171593848 _filtered {} _filtered {} _filtered {} _filtered {} _filtered {}#yiv3171593848 #yiv3171593848 p.yiv3171593848MsoNormal, #yiv3171593848 li.yiv3171593848MsoNormal, #yiv3171593848 div.yiv3171593848MsoNormal {margin:0in;font-size:11.0pt;font-family:"Calibri", sans-serif;}#yiv3171593848 a:link, #yiv3171593848 span.yiv3171593848MsoHyperlink {color:blue;text-decoration:underline;}#yiv3171593848 span.yiv3171593848EmailStyle29 {font-family:"Calibri", sans-serif;color:windowtext;}#yiv3171593848 .yiv3171593848MsoChpDefault {font-family:"Calibri", sans-serif;} _filtered {}#yiv3171593848 div.yiv3171593848WordSection1 {}-->Jim,  On this particular topic, we will agree to disagree.    There is a difference between reliability of a component and its spec variance.  I believe that the ARC-21/65 needed “some selected components” and the 5814S is the proof.  The ARC-38 did not suffer from this, as any garden variety component worked in it. When I worked at Collins, we tested new designs with components form different production batches and suppliers to make evaluate the design stability. Critical circuits were validated by exercising the possible variances of each components.  We temp tested and exceeded the temp/voltage ranges by 30%. If it did not work, we were going back to drawing board.  As a design manager and later design executive, my approach was to force my designers to use the standard supply chain components, and only in special cases, I allowed to use selected components.  A selected component costs multiple times as much as a standard production one, and creates supply chain issues (new PN, new procurement, more cost, more inventory, more taxes and unhappy customers).   Already in the 70s, designers at Collins (HP and others) designers were discouraged from designing products with tuning/adjustments like pots (etc.), as they required extra manufacturing time. This approach required better quality designs.  I think that my feelings about the ARC-21/65 are not very positive, as I think that this product was half-baked when it entered production.  Later efforts improved the product.  Again, I enjoyed this conversation, but forgive me for disagreeing with you 😊  Best, Francesco
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