[time-nuts] HP 1631D Oscilloscope

[Neville Michie]

Hello all,
I hope it is not too far off topic,
My HP 1631D logic analysing oscilloscope has just given a sad gasp.  
The display has a horizontal line of dots with some wandering  
vertical spikes.
The manual does not mention the display unit. The main board does not  
have any smoking craters on it. A test point for 5 or 6 power  
supplies measures OK for each supply. I am in Sydney, Australia, or I  
would just buy another unit on ebay and swap cards till it worked.  
Just to freight a unit here costs about $400.
Does anybody recognise the symptoms or have detailed circuit of  
display and mainframe?

I use the scope for examining the phase problems for the drive for a  
free pendulum. Being a digital CRO I can trigger before the event and  
watch a few microseconds before events at 1HZ.
It appears that one of the limits to accuracy of a free pendulum is  
the detection of the phase of the pendulum and the sensing of the  
exact amplitude of swing.  I use 1MHz inductive proximity detectors  
(home brew) to detect the pendulum movement.
I run a Phase locked loop from the pendulum at 1kHz which divides  
down to the one hertz drive. The pendulum drive is a square wave.
I compare the pendulum to a quartz crystal in an oven.
I wish to pursue the pendulum problem until I am limited by gravity  
tides or seismic noise, or find out the reason why.

It would be great if anyone could help me with the CRO problem,
Neville michie