Re: 561 scope extender wiring?


I had an "interesting" afternoon. First I made the extender (including running coax for the other pins even though it looks like you're right and the 3S2 doesn't use them).
Then I slipped while measuring the voltages at the plug-in and took out the regulator in the 561A. Actually the +300 was wide-open, almost to the +420 unreg. That took a while to find - because the added diode (to prevent the grid on the 6AS7 from going positive) that shorted was 1) not in the manual OR the change info in my copy and 2) well-hidden under the resistors on the ceramic strips! Fixed that.
Moved the extender and another "zap". One tiny strand of braid had touched the 120 VAC next to it. Replaced the scope fuse and cleaned THAT up.
Plugged the extender cable back in - nothing working on the plug-in... then red glow and bubbling from the 561A!! Fried half of R667. Then I realized I'd plugged the cable into the wrong edge connector on the back of the 3T77A. Why did Tek make them identical.... sigh.
Time for a break.

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