[TenTec] Ig drift on amps

Gary Smith Gary at doctorgary.net
Wed Feb 11 16:05:51 EST 2009

> If the leads to the caps are black then that says "they are heating".  Loose 
> connections can cause this.  Make sure the mounting screws are tight and 
> that a proper internal tooth lock washer is installed between the wire 
> terminal and the capacitor terminal. Same for the bottom side with the lock 
> washer between the capacitor and chassis.  Due to circulating currents in 
> this circuit any and all contact resistance can spell problems.  Heating 
> causes resistance to change which causes loading to change which causes grid 
> current to change.
> 73
> Bob, K4TAX

Here's a photo of the blackened wires. If you look at the two small 
doorknobs below & under the toroidal transformer, you will see the 
two un-shielded wires going to the top of them which are black. the 
proximal part of the wire going to the cap which is poking out from 
below the transformer has no black close to the bandswitch wafer. 


the cap which is to the rear of the bandswitch and between the two 
coils (better seen in the link below) is C15. In this amp it is a 
15KV Series HEC HT57 doorknob and all the other doorknobs are 5KV 
828s doorknobs. Looking at the photo in the book shows it at a 
different location and that an offlist reply suggested bumping this 
value to 7.5KV makes me think this may have been an aftermarket 

Anyone know if this cap is stock? There are no KV values on the 

Looking at the top of that cap, you can see darkening around the 
inside lip from 9 to 1 o'clock and around the 2 clock position it's 
absent. I wonder if there's a significance in that? 

I ordered replacement padding caps for all but this one as it's the 
heftiest of the bunch but that darkening has me wondering.



I've ordered replacement padding caps caps 

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