[Milsurplus] RT-128/ARC-21 vs RT-311/ARC-38

[antqradio at sbcglobal.net]

As a guess, the problem was isolated to just that one IF deck that may have been assembled late on a Friday afternoon!
Modern pick, place and  IR soldered assemblies have a much better chance of having the error in every unit.  One of the duties at the  last job I worked before retirement was maintaining one of those large outdoor LED displays, something like 20 by 80 feet.  We had a heck of a job to replace modules due to LED failures, of all things.  Hate working up high on ladders.  Sign company sent techs out to replace all of the dead LEDs which was turning out to be mission impossible with more failing every week.  
I had no documentation on the modules but was able to research the LED driver IC using the part number and discovered that every module had the wrong value of resistor installed that set the maximum current through the green LEDs.  After pointing out the error, the manufacturer replaced the entire screen!Fun times,Jim

      From: grasshopper <grasshopper at epix.net>
 To: 'Jack Antonio' <scr287 at att.net>; milsurplus at mailman.qth.net 
 Sent: Monday, March 21, 2016 5:23 PM
 Subject: Re: [Milsurplus] RT-128/ARC-21 vs RT-311/ARC-38
   
Jack,
    Suspect it is fairly common and wonder how many radio's still
worked, or were working well enough to be put in service?  I found a wiring
error on a Motorola R390A IF deck that impact AGC functionality.  Was it one
IF deck, or a whole series, one wonders...

Steve
Kd3ht

-----Original Message-----
From: Milsurplus [mailto:milsurplus-bounces at mailman.qth.net] On Behalf Of
Jack Antonio
Sent: Monday, March 21, 2016 4:13 PM
To: milsurplus at mailman.qth.net
Subject: Re: [Milsurplus] RT-128/ARC-21 vs RT-311/ARC-38

On 3/21/2016 4:39 PM, antqradio at sbcglobal.net wrote:
> Ray
> I cannot find any published reliability data on the ARC-38, 618S or 
> 618T transceivers.  Everything out there seems to be opinion with no 
> actual data to backup the claim so I cannot comment about the better 
> reliability you mention.
>
While working on my RT-311, I wound up buying a naked chassis from Fair, 
to strip the connectors out of to make
extender cables.

While removing the connectors, I found a total of 3 unsoldered 
connections, hidden by the insulated sleeving.

After the extension cables were made, I discovered the cause of the 
intermittent in the SMO, which was a busted
wire in one of the blue Amphenol hex connectors. Looked like the wire 
was nicked when the insulation was stripped.

Just wonder how much of the reliability problems with this vintage of 
radio were due to assembly issues like this.

Jack Antonio WA7DIA/4
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