[time-nuts] HP5065A

[Magnus Danielson]

Fellow time-nuts,

I now have three 5065A in my lab (not all mine) and I can now conclude 
that the A15 PSU board C8, C9 and C10 caps has gone bad on all three. 
The only difference on the first one is that the process has not gone as 
far as to blown the caps, but two of the leads has began the process and 
turned dark purple on the upper half. Also, one of the caps have been 
replaced by a 220 uF cap at some time.

I already have some fashinating photos of the two other boards lying 
around (on Facebook actually...).

I've already stocked up on replacement caps so replacing them all will 
be my first priority.

Another difference I've noted is that the last one in (Thursday to be 
exact, arrived with two cesiums from a fellow time-nut) proved much more 
modern. The A15 assembly does not even have the rectifier diodes on it, 
but it has been placed off-board. I think this is to provide better 
cooling and I seriously consider to modify the other two up to that 
standard. The rectifier diodes don't get sufficient cooling as it sits 
in its compartment, all sides but the top being closed and then only 
perforated holes for self-convection.

Mounting the rectifiers onto the large aluminium frame would better cool 
them over time.

Another surprice in the later 5065A is the 5061-106 retrofit, where the 
105 oscillator is being replaced with a 10811 oscillator. Will be fun to 
compare against the older variants.

Lack of time for lab duty and lack of space in lab is main obsticle 
right now, but it's fun with some progress at least.

Once I got these three rubidiums of the actual bench, there is a bunch 
of cesiums to investigate.

Need to come up with a suitable measurement rig for all this now. This 
morning I was considering the use of either one of my 5,000055 MHz OCXOs 
or the 5,000055 MHz out of the TS-105A rubidium (BNC on the back) to set 
up a DDMTD system with a bunch of channels. I start to need it for real 
now...

Cheers,
Magnus