Ed
Given that the divider load current, if one substitutes a 5V CMOS
flipflop for the 7474, only increases to about 5mA pp, using a 74HC74 is
probably prudent given the PCB layout used, in that it may avoid EMI
issues that may be a problem with faster logic. However it may then be
prudent to attenuate the output of the divide by 2 fliflop to avoid
overdriving the following emitter coupled pair.
Bruce
Ed Palmer wrote:
The schematic is available here:
http://www.murgatroid.com/t_and_m/hp-00105-6100-figs.pdf . It's also
available with circuit description & waveforms here:
http://www.kennethkuhn.com/hpmuseum/scans/hp5065a_part3.pdf on pages
93-101 (pdf pages - not document pages). However, this copy doesn't
show the schematic for the power supply board. I also see that
document page 8-54 is missing which might be the problem.
Ed
Bruce Griffiths wrote:
If you send me the schematic for the circuit in which its used I can
answer that question better.
Bruce
Ed Palmer wrote:
Perhaps, but given what it's replacing and what it's driving, is the
difference significant?
Ed
Bruce Griffiths wrote:
Ed Palmer wrote:
Yes, I have the same configuration. The part number for the
divider board is 05061-6165. The 10811 + daughter boards are used
in the 105B, 5061B Cesium, and the 5065A Rubidium. The circuit
loading problem is exactly the kind of issue I was expecting.
Thanks for the warning. I could probably resolve it by replacing
the existing 7474 with a 74HCT74, but I'd like to minimize the
amount of hacking I inflict upon the unit.
Ed
A 74AHCT74 would be a superior replacement.
Bruce
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