[ARC5] [Milsurplus] BC-221AK Question

[Mark K3MSB]

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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