[ARC5] 70+ year old errors found and corrected.

[Bill Cromwell]

On 06/10/2013 08:44 PM, Kenneth G. Gordon wrote:
> You know that 1.5 - 3.0 MHz coil box I was having troubles with? The one out of the receiver
> that had been hacked for crystal control back in the 1970s?
>
> Well, today, not having anything much else to do (yeah, right), I decided to take a closer look
> at it to see if I could figure out exactly what was wrong with it.
>
> First, since the HFO coil had been the one that had been messed with (I figured this out
> when I looked at the screws holding the coil in the box: there were 2 different kinds, and the
> paint had been "broken").
>
> Although I had restored the two resistors, R-3 and R-6 to their original values, the HFO still
> didn't work. I looked more closely at the connections to the coils and after taking my glasses
> off and looking VERY closely, I discovered that one lead of the plate coil was no longer
> soldered to its connection. What looked at first like solder was flux, and all 6 of the Litz wires
> were not soldered. When I had tested the coils for continuity, I had clip-leaded one lead of the
> ohm-meter to one end of the coil, and had used the probe on the other end. The clip-leaded
> end turned out to be the open one....of course.
>
> Have any of you 70+ year old folks ever attempted to 1) clean the enamel off of 6 pieces of
> #60 Litz wire, and then 2) solder them in place with shaky hands? Well, I managed...finally.
>
> Putting it all back together and installing in my working receiver, I found that the HFO was
> now working, but the signal through the mixer was way down. However, the RF amp did peak
> by the Align Input control, so that meant that the RF amp coil was OK.
>
> Back to the coil box. After swapping the good coils, one at a time from my working coil box
> into the non-working coil box, I zeroed in on the mixer coil as the culprit. Obviously, however,
> the coil had never been tampered with as the screws still had their red paint on them and
> they were very tight.
>
> Even so, I removed them with some effort, and removed the coil. Using my clip-lead and
> ohm-meter I again determined that both coils had continuity. Furthermore, there were drops
> of the original ruby-red enamel on all the connections.
>
> Then, remembering my experience with the HFO coil, I used both of the ohm-meter probes,
> without any clip-lead, to check continuity through the connections at the bottom of the coil
> from outside it.
>
> Sure enough: one coil no longer had continuity.
>
> Again removing my glasses, I looked VERY closely at the two connections of the now open
> coil, both of which looked "factory" and both of which had that ruby-red enamel on them.
>
> One of those connections had never been soldered: the Litz wire had been wrapped around
> the connection, never soldered, and then had been covered with ruby-red quality-control
> enamel.
>
> A 70+ year old construction error, followed by a quality-control error uncovered.
>
> A few seconds with the soldering iron and solder fixed the problem.
>
> Re-installing the now repaired coil box proved that the receiver was now working properly.
>
> Alignment followed, and I am now listening to it.
>
> Sheesh!
>
> Ken W7EKB
>

Hi,

The most glaring assembly failure I found was in a piece of gear that 
never failed. I had a large digital frequency counter, full of vacuum 
tubes and good to something slighly over 1 mc. I used it to set the 
adjustable frequency PL tone cards in commercial radios (until I 
replaced it with something easier/faster). Over several years I offered 
it to anybody interested in mil surplus including right here (grin). 
Several times. So no griping. I stripped out various parts that I 
thought I might use and scrapped the rest. While removing the parts I 
found a ground wire from a three tube module that had never been 
soldered. The wire was merely wrapped around the ground lug. In all the 
years and travels of that unit (at least while I had it) it *always* 
worked. Shrug.

73,

Bill  KU8H