DP501 digital prescaler

Dave Casey

Yes, the DP501 is designed to work with specific TM500 counters and uses a
backplane signal to tell the counter that the input has been divided. The
counter also can enable/disable the prescaler (even over GPIB in the case
of the DC5009). See the DC5009 manual for more info about the signals

Dave Casey

On Sun, Jul 14, 2019 at 5:45 PM walter shawlee <@walter2> wrote:

I have one of these (an din mind condition, probably because nobody ever
used it), and have not been able to find a manual anywhere, so it's hard to
answer this burning question:

why on EARTH does it divide by 16? how is this good for anybody in
practice? every other prescaler on earth (including the ones in other Tek
counters) provides effective divide by 10 results so the data is instantly
usable, but this item does not. Is there some mystical way it fixes that
by a rear panel connection I can't see (thanks to no manual)?

I have tested it, and YES, it does in fact divide by 16, and mine worked
up the 1.6Ghz with no trouble.
what I can't figure out is why it works this way with other Tek counters,
like my DC503, which has a GHz indicator, but makes no special use of the
DP501. I feel like there is an answer out there, I am just not sure where
it is hiding in all the Tek docs. Are there some magical backplane
connections that make this work correctly? I would really like to know.

any help appreciated,
walter (walter2 -at-
sphere research corp.


From my "library" of TM500/5000 information it looks like: the DP501 was available from 1984-1993. In 1984 the description mentions the DC5009 and DC5010. In the 1985 catalog pg372 it says: "The DP501 Digital Prescaler adds 1.3GHz frequency counting capability to the Tektronix DC503A, DC509, DC5009, DC510 and DC5010 Universal Counter Timers." I have a 125MHz DC503A counter and it does have a GHz indicator light. I could not find any mention of the DP501 in the manual. I checked the 070-2088-04 Rear interface data book and could not find the DP501 in it either. I found a ServiceTEKNote at that appears to cover setting up DC503A to DP501.