lost an LM709N in my ST-6. anyone know if SN72709N is compatable with the LM709N? I have not been able to locate a spec sheet on the chips... I see a bunch of SN72709N's listed on ebay and if compatable, I will grab a few. If they are not compatable, anyone know where I can purchase the LM709N's? THANKS! Ken, W9AEK