Re: 3T77 tunnel diodes (again)


 

After adventures in (mis)using my homemade extender cable (different thread), I FINALLY got back to working on the plug-in. D22 (unobtainable 1N3129 20 ma TD) just would not trigger no matter what, just sat there around .025 volts and wouldn't get much higher despite adjusting its bias (R21) all the way up. At one point the other TD (D25) fell out of its clip. The factory solder joints hadn't penetrated through the vias far enough and the clip had worked its way loose. Resoldered that. D25 then showed .057v and by tweaking its pot, could be seen to snap from low to high state... I swapped D22 for D42, the trigger regeneratorand it started merrily free-running, stops when I reduce the Trig Sens as intended, and triggers on my 114 pulse generator :)

So now I need to figure out a mod to use some other TD in place of D42. Seems easier than modifying the two-TD trigger circuit.

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