[ARC5] [Milsurplus] BC-221AK Question

Tue Sep 2 21:20:59 EDT 2025

I have a dozen or so of the 'bathtub" type capacitors that these units use
so if any one needs them, let me know.  Free for postage.
W44NPN

On Tue, Sep 2, 2025 at 9:11 PM Mark K3MSB <mark.k3msb at gmail.com> wrote:

> Installed the 250 H choke from a donor BC-221-M "Hanger Queen" with the
> correct 0.001 uF bypass cap....
>
> [image: image.png]
>
> The style and size of the 250 H choke from the -M is different than the
> 150H choke for the -AK, so I had to mount the choke on the chassis side.
>
> Powered it up.... and it works!   I was STUNNED that the settings for 3885
> Kc actually produced a signal at 3885.19 Kc !!!!!
>
> Need to play with it more tomorrow.....
>
> 73 Mark K3MSB
>
>
>
>
>
>
> On Tue, Sep 2, 2025 at 11:47 AM Mark K3MSB <mark.k3msb at gmail.com> wrote:
>
>> Over the weekend I rebuilt the power supply.   It's using the original
>> chassis and it's not going to win any prizes,  but it's providing 150V
>> regulated voltage and 6.3 VAC now.
>>
>> Added a new cord and fuse etc.   The internal wiring was horrid;  I'm
>> surprised it didn't short the B+ at some point....    fixed that stuff.
>>
>> A winter project is going to be doing a complete rebuild of the PS on a
>> new chassis.
>>
>> The audio choke in the picture I posted is obviously not 150H..... in
>> fact at 1 Kc it measures 1H.
>>
>> I have a hanger queen BC-221M and I extracted the choke from it.    Its
>> 250 H at 1 Kc and it will have to do,
>>
>> Of course, the form factor is different so I'm going to have to bolt it
>> on.
>>
>> [image: image.png]
>>
>> 73 Mark K3MSB
>>
>>
>>
>>
>>
>>
>>
>> On Wed, Aug 27, 2025 at 8:34 PM Mark K3MSB <mark.k3msb at gmail.com> wrote:
>>
>>> Hi Ken
>>>
>>> >> The cap is part 9-2, not 0-2 and it is supposed to be 0.001 uF.
>>>
>>> Yes, my typos.   Too lazy to roll over to the bench and get my
>>> glasses........     :-)
>>>
>>> [image: image.png]
>>>
>>> .... and thus the motivation for my question....
>>>
>>> [image: image.png]
>>>
>>> [image: image.png]
>>>
>>> The internal HB Power Supply was a "Widow-Maker" Special......with leaky
>>> caps!!!
>>>
>>> I will rebuild the PS tomorrow and power it up (after dressing the
>>> connections associated with the replacement components.....and using the
>>> correct parallel capacitor.
>>>
>>> 73 Mark K3MSB
>>>
>>>
>>>
>>>
>>> On Wed, Aug 27, 2025 at 7:46 PM Kenneth G. Gordon <
>>> kgordon2006 at frontier.com> wrote:
>>>
>>>> On 27 Aug 2025 at 18:56, Mark K3MSB wrote:
>>>>
>>>> > I have a BC-221 whose ID plate says  BC-221E.   It is not an E
>>>> > variant.
>>>> > From the tubes, front panel controls, and TM11-300,  I think it's the
>>>> > AK variant.
>>>>
>>>> I have two -AKs here: unfortunately. in storage, not in the shack. :-(
>>>>
>>>> > Looking at the front panel,  what is supposed to be behind the two
>>>> > antenna connectors?
>>>>
>>>> Well, only ONE is an antenna connector: the "other" one is a ground
>>>> connector...or should be.
>>>>
>>>> > I tried discerning it from TM11-300.   I think it's supposed to be a
>>>> > 150 H Choke (Part 24) in parallel
>>>> > with a 0.01 uF cap (Part 0-2).
>>>>
>>>> The cap is part 9-2, not 0-2 and it is supposed to be 0.001 uF.
>>>>
>>>> >    Can anyone confirm?
>>>>
>>>> Well, a 150 H choke would be physically fairly large for a "small"
>>>> choke. I would have to go to my storage building and open one of my -AKs up
>>>> to check, and cannot do that just now.
>>>>
>>>> I hope Wayne can help. If all else fails, I'll make a run to my storage
>>>> and take look as soon as I can.
>>>>
>>>> BTW, the -AK version is one of only two other versons which include AF
>>>> modulation capability. None of the others have that. This makes the -AK a
>>>> fully functioning signal generstor.
>>>>
>>>> Ken W7EKB
>>>>
>>> ______________________________________________________________
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-- 
Frank Barnes
www.W4NPN.org <http://www.W4NPN.net>
Chapel Hill, NC
Grid Square FM05
Cell 919.260.7955
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