Re: 2247A 2252 Timer Counter Reference

 

After several failed attempts to put the following reply in the thread "2247A 2252 Timer Counter Reference" I'm trying via the general "Conversations" page. Previous attempts landed in the "C: Lot of 5 Tek 453's" thread.

My apologies if this doesn't work either.

It's been a while and I didn't take notes but I remember that I could see that the phase info (U1902 PFC, pin 23) was dead (steady state). Of course, I first looked at TC1 (pin 1) and VCO (pin 26) and found both alive and well, so the X-tal oscillator and U1904D (level shifter) couldn't be the problem. Partly just for confirmation of my conclusion, I decided to just cut pin 23 (PFC) and put in one gate of a socketed 'LS86 between pins 1, 26 (inputs), and 23 (output). Works a treat! As said, a bit rough but accurate and stable. I think that i didn't even put in a pull-up resistor at pin 23, which strictly speaking shouldn't be necessary but may improve shape and level. Of course, a bit of HF jitter does no harm in this application and is actually inserted through pin 22 (Noise).

Raymond

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