Reconditon av Dynaco SCA-35Shape before changes. Note original dynaco tubes!
The EL84 was toast. The 7199 has broken down isolation filament<>catode and had to be replaced. This is done wuth GB-1252, a strengtend version of 6U8A and an adapter to change pinout. 6GH8 is an alterative tube with the same pinout as 6U8, ECF82 the european name.
Replacement tubes in place.
This instability occures both with the original 7199 and the replacement tubes. It's cured by grid and screen stoppers.
Same amp with stoppers installed.
EFB module installed
Finally the american style power cord replaced by an IEC power inlet.
Removal of the powercord gives place for dual mains fuses.
Feel trapped ?