[time-nuts] HP 5370A

[Didier Juges]

I got an HP 5370A from eBay which did not work at power up (display was 
messed up). After resetting all the ROMs and the CPU in their sockets, 
the instrument came to life and now powers up without error message. It 
has serial number 2128A01306.

However, it seems that the reference oscillator output is severely 
distorted (when I look at it with the scope), it looks more like 900mV 
p-p of 30 MHz than 10 MHz, even though the instrument does not complain. 
The output looks the same if I drive the external reference or use the 
internal reference. When I measure the reference output with the 5370 
itself, I can make it display 10 MHz, 20 MHz or 30 MHz just by adjusting 
the threshold pot.

I have posted a picture at http://www.ko4bb.com/Test_Equipment/HP 
5370A_ref_output.jpg

Also, I went through the instrument check out, and the first step, page 
3.4, shows how to read the period of the reference oscillator, and the 
instrument displays 0.00 instead of 100.00. It obviously does not like 
the reference output signal.

The time base is an 10811-60111, I believe this is the "standard" time 
base, as the manual lists the "high Stability" time base as a 
10544-60011. The 10811 is a pretty nice "standard" time base :-)

Otherwise, the time base seems very close, my reference oscillator (a 
3586 synchronized to WWV until my GPS clock is finished) displays 10.000 
000 100 on the 5370.

So it seems some of it is working, but the reference oscillator output 
bothers me, and so does the impossibility to run the check out..

Any help in figuring out if this is normal would be appreciated.


Thanks in advance.

Didier KO4BB