[ARC5] BC-946 capacitor plates shorting?

[JAMES FALLS]

Similar story here: I restored an old beat up Delco AA5 and everything in the lower 1/2 of the dial was gone because of several slightly bent plates in the rotor of the VC. I ended up sliding a single edged razor blade between the plates to even out the spacing. 

Jim Falls K6FWT 

> On Nov 9, 2021, at 19:20, Scott Robinson <spr at earthlink.net> 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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