It's the latch in the switch that isn't working. It has to do with the little sprung rod thing and its small sprung cover. Now I look at it the FET switch isn't latching either. Never used it. But I see no difference from the other two switches that do latch perfectly.
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The mechanism gets dirty.
The CRC 556 lubricates it and solves the problem.
It also cleans up the switch contacts and eliminates erratic switching.
I have repaired many 7CT1Ns and many 576s by this method. I have seven 576s that been made operational with this method.
A few drops of CRC 556 down the switch shaft while the front panel is facing up will allow the lube to enter the switch body.
Apply it and work the switch a dozen times.
RP
ROLYNN PRECHTL K7DFW