UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - Marconi TF2431 Counter Service Manual / Schematic

brian_mk · 30th Jul 2020, 11:25 am

From my earlier investigation, I think the schmitt trigger is working as it should.
If I've understood things correctly, the hysteresis is set by the diode forward voltage drop and is about 0.7V.

I'm pretty sure the problem is the interfering signal that I can't get rid of.
The counter makes a pretty good wideband receiver.
If it was FM broadcast, I would have expected to see a whole bunch of frequencies and general noise rather than a fairly clean looking signal that the scope can sync to.

30th Jul 2020, 11:25 am	#14
brian_mk Tetrode Join Date: Mar 2015 Location: Milton Keynes, Buckinghamshire, UK. Posts: 91	Re: Marconi TF2431 Counter Service Manual / Schematic From my earlier investigation, I think the schmitt trigger is working as it should. If I've understood things correctly, the hysteresis is set by the diode forward voltage drop and is about 0.7V. I'm pretty sure the problem is the interfering signal that I can't get rid of. The counter makes a pretty good wideband receiver. If it was FM broadcast, I would have expected to see a whole bunch of frequencies and general noise rather than a fairly clean looking signal that the scope can sync to.