[ARC5] First Post and Questions

[Bobby Drummond]

Robert:

As a follow up, I took the BC-457 A further apart and you are indeed
right.  In the center of the tank circuit "tower" was the same type of
powdered iron "knob" attached to the end of the screw that goes down
through the center threaded hole. The powdered iron part was chipped
serrated where it would have been joined to the end of the screw and the
indentation of the screw end was at the center of the powdered iron (you
could tell that they were joined at one time.

Further proof was found when I took the cover off the oscillator coil
shield there was on just like the one in the center of the tank circuit
"tower".  It was intact and I could clearly see it was exactly as you
described.

Do you know where a good place to get a new one would be?  I have no
experience buying parts for these transmitters.  I have heard that Fair
Radio Sales in Ohio is a possible source.


73 de AK4JA

On Mon, Jul 3, 2017 at 6:53 PM, Bobby Drummond <alphak4ja at gmail.com> wrote:

>
> Thanks, Robert, for the information.
>
> Yes, in retrospect, getting a BC-458 would have been an easier go in some
> ways, assuming that it had not been altered, and of course had one been
> available, which was not the case where I looked.  At this point, I am not
> ready to start regretting my decision though. I think I can make do with
> what I have OK.
>
> The octal socket installation instead of the original connector is a
> negative I can live with.  I knew it was there when I looked at the rig on
> the table and knew someone had altered the transmitter to some degree. At
> the time, I just didn't know, for sure, how much someone had altered it I
> should, with a little patience and persistence, be able to determine the
> full extent of any alterations in the near future.
>
> Thanks for the insight on the "ferrite" material question.  So, it must
> have gotten broken off from a hard jar or fall maybe from the end of the
> adjusting screw in the top center of the "tower".   What's the worst that
> could happen if it is removed?  The final's output may not be full on when
> someone tunes down to the lowest available frequencies?  I could live with
> that if necessary since I will be using the upper end of the range of
> frequencies and don't plan to use the lower at all.  (My guess is that both
> upper and lower ends will be affect some by the removal of the
> "ferrite/powdered iron" piece, but the lower will be affected the most)
>
> While I would love to do a full-bore-back-to-factory restore on the unit,
> that can never be with the unit I have.  I'll just have to be happy with
> getting it working well enough to put it on the air on the band I would
> like to have it working on - 60 meters.
>
> At this point, I've got of learning to do about the old Western Electric
> made BC-457 A unit, that's for sure.  I'm looking forward to it.
>
>
> 73 de AK4JA
>
>
>
>
>
>
> On Mon, Jul 3, 2017 at 6:14 PM, <WA5CAB at cs.com> wrote:
>
>> Bobby,
>>
>> My first comment is that you should probably have bought a BC-458, which
>> already tunes 5.3 to 7.0 MC.
>>
>> In a message dated 07/03/2017 15:40:45 PM Central Daylight Time,
>> alphak4ja at gmail.com writes:
>>
>> Thanks, Dennis, for the welcome and the information.
>>
>>
>> The rig, as far as I can tell at this point, has had one modification:
>> the power input point at the back of the transmitter is an octal socket,
>> not the original type connector.  To me, that's not a big deal because, as
>> far as I know, I will not ever use a dynamotor power supply to operate the
>> transmitter. I would like for the transmitter to be pristine, but it wasn't
>> when I bought it in Dayton.
>>
>>
>>
>> Prying the original 7-contact connector out of the back of the
>> transmitter and replacing it with something else (most commonly an octal
>> tube socket) is perhaps the most common (and most unnecessary) modification
>> to a Command transmitter.  It generally precludes any restoration to
>> original condition.  And more often than not means that the internal wiring
>> is nowhere near original.
>>
>>
>>
>> There is one other thing that I have just noticed and have concerns about
>> right now.  There is something loose inside the ceramic "tower" that the
>> 1625s plates are connected to. This tower is part of the 1625's tank
>> circuit as best I can tell.   It appears that there is a ferrite material
>> that fits inside the coupling coil assembly.  This ferrite material is
>> loose and rattles around if you pick up the transmitter and shake it.  It
>> can drop completely out of the coupling assembly under the right conditions.
>>
>> This is just a guess, but I think the ferrite material belongs inside the
>> coupler (not something that accidentally fell into the "tower" and is used
>> to increase the inductance of the coupling coil.
>>
>>
>> Does anyone know if I am correct?   If so, what was and what is now
>> normally used to secure the ferrite material to the inside of the coupler?
>>
>>
>>
>> You are not correct.  Attached to the top of the PA tank coil form was
>> originally a 3-legged holder for an internally threaded tube.  In the tube
>> was a large slotted head screw.  Molded to the bottom end of the screw was
>> a probably powdered iron tuning slug which was at the factory used to track
>> the final to the tuning dial at or near the bottom of the tuning range.
>> The middle of the three tuning capacitors under the chassis was or is the
>> trimmer capacitor use to track the PA at the top end of the tuning range.
>> I have never investigated it but as far as I can tell from the parts lists
>> in the three different manual groups, the same tuning slug (E-59) is used
>> in all of the transmitters.  So finding a good replacement should be no
>> problem.
>>
>> The rotary coupling coil (AKA variometer) is air core.
>>
>>
>>
>> 73 de AK4JA
>>
>>
>>
>>
>>
>> Robert Downs - Houston
>> wa5cab dot com (Web Store)
>> MVPA 9480
>
>
>
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