[ARC5] BC-946 capacitor plates shorting?

[Scott Robinson]

I'll  add that the resistors should be 10W rated.

/scott

On 11/9/21 5:53 PM, Scott Robinson wrote:
> If your short in the tuning cap is persistent, try this, which I have 
> used and it works:
> 
> 1) Disconnect anything in parallel with the tuning cap.
> 
> 2) Find an adjustable 300V power supply, doesn't have to be regulated.
> 
> 3) Connect a 10K resistor in series with the hot lead, and connect that 
> to the floating side of the cap. Connect the low side of the power 
> supply to the cap frame.
> 
> 4) Turn the voltage up until you see teeny sparks as you rotate the 
> tuning cap. run the cap back and forth until the sparks cease, and maybe 
> blow some compressed air through it, too. Raise the voltage some more 
> and repeat. If you get 100-200V or more with no sparks, you're done. You 
> can try a smaller resistor value ( maybe 3k) if you like.
> 
> This will fry any metal whiskers present.
> 
> FWIW,
> 
> Scott Robinson
> 
> 
> 
> On 11/9/21 4:59 PM, J Mcvey via ARC5 wrote:
>> Another possibility is that is has some debris or has grown metallic 
>> hairs ( yes this really happens!).
>> The quick approach would be to crank up a compressor, if you have one, 
>> and blow the debris out while the plates are unmeshed. This works 
>> about 75% of the time.
>>
>> BTW , you will have to remove the coil pack  if you want to do an ohm 
>> check, otherwise you will read the low resistance of the parallel coil.
>>
>>
>>
>> On Tuesday, November 9, 2021, 06:33:57 PM EST, Kenneth G. Gordon 
>> <kgordon2006 at frontier.com> wrote:
>>
>>
>> On 9 Nov 2021 at 14:17, Waldo Magnuson via ARC5 wrote:
>>
>>  >    Any fix suggestions would be appreciated.  Removing the gang 
>> capacitor looks messy.
>>
>> Actually, it isn't difficult at all, since it was designed to be 
>> easily removable.
>>
>> There are 4 larger screws in a box pattern on the front-panel which 
>> hold the cap to it.
>>
>> You will first have to remove the inner cover over the cap, then 
>> unsolder 3 wires, one of each
>> which goes to a section of the cap. They are easy to reach.
>>
>> Then unsolder the wire which goes to the antenna post.
>>
>> Remove the 4 screws, then simply lift out the cap.
>>
>> FYI, the tuning capacitors from the MF receivers, either the BC-453 or 
>> the R-23/ARC-5 are
>> identical to the BC band tuning cap.
>>
>> If your cap is damaged, one from either of the two receivers mentioned 
>> above can replace it.
>>
>> But, as others have mentioned, an ohm-meter will tell you if/where it 
>> is shorted. As also
>> mentioned, it may simply be that the cap is no longer grounded.
>>
>> Ken W7EKB
>>
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