[ARC5] SCR-274N Update - There be AM Here!

[Mark K3MSB]

Hi Guys

I was successful in getting my SCR-274N to squirt out some AM this week!
Here's the saga with a follow up question.

I managed to purchase a few NOS Raytheon handheld carbon mics recently.
Not "era" for the ARC5s, but they were NOS Carbon Mics still in the plastic
wrapping paper and I got them for about $3 each, so my wallet was out of my
pocket in a flash.   A transplant into my T-17 may be in the future….

They are 4 conductor mics (2 for switching, 2 for the mic element) and I
elected to just use the K-56 button on the BC-451A for initial testing.
Got the wires tacked onto the plug, tuned up on CW and set the IC-756 Pro
III for monitoring, went to AM and hit K-56 and spoke into the mic -  I
heard some nice AM before it went down into the mud.   To make a long story
short, pressing K-56 after going from CW to Voice on the BC-451 did not
cause the Dynamotor to stay on  Nuts.

After some investigation I found that one of the relay pairs on the BC-451A
were not closing in the VOICE position.  Some gentle bending with a pair of
needle nose pliers solved that. I tried it again and heard some nice AM on
the Icom!   Well mostly; the audio level dropped down all of a sudden and I
haven't checked into that yet, but there is still AM being heard!

Afterwards I reopened the BC-451 as I decided to clean the contacts on the
BC-451.  I buttoned everything up after cleaning and got the 451 installed
in my setup and went to CW.  The dynamotor spun up and when I hit
K-56…nothing.  Zippo.  I tried my straight key and the same thing.  No
power output.  Oh Crap, now what did I do?

Here's what I found.  There are "banana leaves" strips on all the jack pins
in the SCR-274N (as well as ARC-5 etc).  Those leaves had fallen off of the
Key line on BC-451 J-12!!  Oh Crap.  So, I sent Mike Hanz an "Oh Crap"
email and asked if I could remove those leaves from a junker  BC-451A that
I had. Mike said it might be possible, so armed with a bunch of fine dental
picks I went forth on a banana leaf removal mission and failed miserably.
They are very delicate and I don't think a transplant operation is feasible.

So, after sitting in my chair and having yet another "Oh Crap" moment, the
good Lord gave me a bit of wisdom and I realized I had a few unused pins on
my J-12.  I did a quick jumper inside the 451 and another fix on the plug
that mates with it (going to the BC-456) and to my delight both CW and
VOICE now work FB OM.  Well, the audio is a bit low but I'll worry about
that later.

So, here's my "follow up" question.  What does one do when the "banana
leaves" decide to come off one of those pins and you don't have any spare
pins?  It's not like Radio Shack has any of those jack lying around, so
what have you guys done for repair in this situation?

Still having a blast working on this stuff!

73 Mark K3MSB

Sent from my Android phone