[ARC5] BC-946 capacitor plates shorting?

[Tom Lee]

Nah. Low-power resistors protectively vaporize if overloaded. It's a 
feature. ;)

Tom

-- 
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070
http://www-smirc.stanford.edu

On 11/9/2021 19:20, Scott Robinson wrote:
> 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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