[time-nuts] HP-59309A Clock counts only seconds

David C. Partridge david.partridge at perdrix.co.uk
Mon Apr 3 21:33:45 EDT 2017

You can get a brand new CD4011BE from pretty much most suppliers at about 15 cents that won't exhibit the problems of the earlier ones.


-----Original Message-----
From: time-nuts [mailto:time-nuts-bounces at febo.com] On Behalf Of Jeremy Nichols
Sent: 04 April 2017 00:44
To: time-nuts at febo.com
Subject: [time-nuts] HP-59309A Clock counts only seconds

I have a new-to-me HP-59309A HP-IB Digital Clock. The clock works on both the internal crystal oscillator and on an external 10 MHz standard (GPSDO). However, it counts only to 60 seconds and then repeats without updating the minutes digit. The TIME SET (FAST and SLOW) push-buttons work but again, the count will not update minutes and hours, only seconds. The DAY SET procedure works correctly for days and months. All the other switches and buttons do what they are supposed to do. Using my 10526T logic pulser I can force the minutes and hours counters to work. 
The power supply is in good condition (after replacement of a few
components) and I see no other problems (yet).

Tracing the clock signal through the logic circuitry brought me to U3 on the A4 board. This (U3) is a 4011 quad 2-input NAND gate in a 14-pin DIP package. It "connects" the seconds counter to the minutes counter and appears to have failed. One of the people on the email list <hp_agilent_equipment at yahoogroups.com> commented that the 4000 series CMOS chips have a known limited lifetime. Since these parts are no longer in production, the writer expressed the concern that any parts I might find to buy may be DOA.

Before I go hunting for parts, I'd appreciate hearing from anyone in the group who has experience with the 59309A Clock and/or the 4000-series CMOS family. In particular, are there modern equivalents to my 4011 chip? If the 4000's really do have a limited lifetime I'd rather use a substitute.

Jeremy, N6WFO

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