[Heathkit] DX-40 Keying trouble

[Robert Nickels]

  On 8/30/2010 6:52 PM, Carl wrote:
>
> CDE admitted they tried a new process and I seriously doubt if any 
> silver was involved. 

I'm not a materials engineer, but the fellow who looked at one of the 
failed CDE disc ceramics from my 75-series HRO-500 was, and he 
recognized the problem immediately, as it's very common in thick-film 
circuits that use similar lead-attach metallurgy.  The tendency of 
silver to creep on ceramic surfaces or into grain boundaries in the 
presence of an electric field means that an alloy of silver-palladium or 
silver-palladium-gold is generally used.    Contact with moisture or 
molten solder accelerate the failure mechanism.

73, Bob W9RAN