[Milsurplus] BC-221 with noisy tuning

[John Hutchins]

Ian -
On some models this was standard tweek adjustment.
Hutch
On 6/10/2013 1:41 PM, Ian Wilson wrote:
> Once I opened up the capacitor compartment the tuning mechanism
> looked rather dry. I blasted the capacitor plates (with the capacitor
> set to max C) with a can of no-residue switch cleaner, and applied
> a tiny quantity of XYL's sewing machine oil to the two bearings and
> the antibacklash gear. This cleared up the warble very nicely.
>
> I notice that this unit has a very nicely made modification: a separate
> ceramic trimmer has been added across the crystal frequency setting
> trimmer. The new trimmer has been mounted behind the nomenclature
> plate and a hole made in the box - but not the plate. The result is that
> you can trim the crystal reference frequency without removing the unit
> from the case, and the modification is invisible once you re-attach the
> nomenclature plate.
>
> 73, ian K3IMW
>
>
>
> On Mon, Jun 10, 2013 at 10:12 AM, J. Forster <jfor at quikus.com> wrote:
>
>> Put a receicer w/ a BFO nearby and listen. Then gently tap things,
>> possibly starting w/ the oscillator tube. When you finde thye thing that
>> warbles you're done.
>>
>> -John
>>
>> ==============
>>
>>
>>
>>
>>> I have a BC-221 with integral power supply. When I monitor the frequency
>>> on
>>> an external
>>> set, tuning slowly has a distinct 'warble' to it. This feels like some
>>> sort
>>> of mechanical problem
>>> (although I imagine it could also be due to something like metal whiskers
>>> on the tuning
>>> capacitor blades).
>>>
>>> Once I stop turning the tuning control the output frequency is rock
>> solid.
>>> I can move it up/down
>>> smoothly with the 'Corrector' control.
>>>
>>> The tuning control doesn't have any grittiness to it when turned, but of
>>> course there could be
>>> backlash in the drive mechanism.
>>>
>>> Suggestions welcomed.
>>>
>>> 73, ian K3IMW
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>>
>>
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