[Heathkit] DX-100B Capacitor Question

[L L bahr]

Bruce,

One last thing.  Since Heath used a .001 silver mica at 2000 volts for their blocking cap, you could substitute two of Mouser's 2200 pf @1000 volt silver micas in series giving you a 2000 volt cap at the correct .001 nominal value.  The Mouser part number for the 2200 pf 1000 volt SM is:  598-CDV19FF222JO3F. (Buy two of them and put them in series).

Lee, w0vt



Bruce,

I had a conversation with Garey Barrell, K4OAH about this and he pointed out there is no 68 pf Silver Mica between the driver and the final tubes.  That coupling cap should be a .001 and not 68.  There is a 47pf cap between the 12BY7 and the 5763 tube.  So are you talking about something else, or do you have the wrong capacitor where there should be a .001 ???  (I'm talking about the blocking capacitors). After the .001 blocking cap you have a pi-network feeding the grids of the 6146 tubes.  There is a variable cap on the input side of the filter and a fixed 47pf cap hanging from the filter to ground on the output side of this pi filter feeding the 6146 grids.  There should be no 68 pf cap of any kind in the entire DX-100. 

Thanks, Garey.

Lee, w0vt



I am rebuilding a DX-100B and saw a posting that it would be a good idea to replace the 68 pF mica between the driver and final.

The existing capacitor is a molded mica Sangamo.  It has no color codes, but on one side is stamped "68 5%".  

On the other side, it is stamped "2000 VW" (not WV).  It is arranged like a 6 dot format, and when you hold it with the arrow pointing right, the digit "2" is molded into the upper middle dot.

Is this a 2000V part ?  A quick check of the Mouser site shows the typically available CDE micas (CDV19) are only rated up to 1000V.  Any suggestions for a replacement ?

Thanks,

Bruce
WB8VCM



 		 	   		  
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