[time-nuts] 3GHz prescaler for Pendulum counters

GandalfG8 at aol.com GandalfG8 at aol.com
Sun Nov 15 06:11:03 EST 2015

Hi Arthur
Thanks for the feedback, that's an interesting find and obviously  
something to keep in mind.
As you know Pawel originally designed the prescaler for the  CNT85/PM6685, 
although in earlier Ebay listings he did comment that it also  worked for 
the CNT80/PM6680, and taking a look at the schematics I can see  now that the 
detection circuit you refer to for the CNT81 is different  to that in the 
CNT80 and also to that in later models.
In the CNT80 the selection resistors were returned directly to  ground, 
that 100K common resistor was introduced with the  CNT81 but was promptly 
dropped again for the CNT85 onwards.
It would seem, in this respect anyway, that you drew the short  straw:-)
Interesting too to see your comments regarding orientation, although from  
the CNT85 onwards this again seems to have been something that was  
Glad to hear you got it sorted though, I'm still more than happy with mine  
and certainly agree that it's a really good deal.

 Just a note to say that I bought one of these
 prescaler boards for my CNT-81. One problem is
 the way the board mounts in the CNT-81 the "in"
 connector is toward the back instead of toward
 the front like some of the other counters and I
 had to make a longer input cable. Pawel does
 now know this and maybe a different cable can
 be included for these counters in case you can't
 make one. Be sure to check on this so there
 aren't any surprises.......


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