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    Building, troubleshooting and testing of these amplifiers should only be
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Sansui 1000A OPT's

jlsem

Member
2003-06-17 1:12 am
Dallas,TX
I have searched the Forum and Googled the web and cannot seem to find a definitive answer to what the primary impedence of these transformers is. 3.2K and 6.6K are the values I get; does anyone know for certain the actual figure?

Also, does anyone know the operating point, B+, and screen voltage used by Sansui?

The true figures will determine how I use these - if it's 3.2K I,ll run 7695's in an experimental transconductance amp, if 6.6k I'll just do it like Sansui but with 7868's.

Thanks,
John
 
That amp used a pair of 7591A valves on the OPT... Basically those are 6L6GC valves that came off the production line with extra testosterone then sorted.....
The Plate was at 470 V @idle... 450V full tilt...
The screen was at 420 V... 400V fulltilt...
The Bias was at - 19 V ....
I did the number crunching with the curve sheets..... 6.6K is correct plate-to-plate load....3.2K would not even come close to working properly.... The power output was about 50 Watts...
I checked data sheets...they also confirm 6.6K as a optimum load and ratted to get 45Watts...
You could always measure the OPT to be sure..... just apply 120V mains across the primary then measure the secondary voltage at say 8 ohm tap...
The voltage ratio squared times 8 will be the plate load....

Chris