[time-nuts] HP 8566B repair

Jeff Mock jeff at mock.com
Thu Dec 6 22:38:13 EST 2007

Does anyone have any suggestions or advice about 8566B repair?

I've had an 8566B for 7-8 years, it's been a faithful tool, never had a 
problem with it.  It's reasonably clean unit that's never seen a tough 
life.  It sits in the storeroom 90% of the time and is on my bench maybe 
10% of the time.

So, this week, after a 4 month hiatus, I've been using it on the bench 
and it starting producing a "YTO UNLOCK" message, the trace seems to 
basically work properly but is clearly unlocked and the trace will 
randomly slide to the left or right.  The Yttrium oscillator is clearly 
unlocked.  I'm hopeful that the problem is in one the control loops 
outside the oscillator module.

I read the repair guide that Agilent kindly keeps on their website, they 
have some good instructions and narrow the problem to 3-4 modules, but 
I've never opened up the instrument and am a little apprehensive about 
making things worse.  My hunch is that the problem is an electrolytic 
cap that has dried out over the years and has failed.

Any suggestions for either self repair or outside repair and 
re-calibration is appreciated...

In full disclosure, I also have a 70908A based spectrum analyser that 
that has much better specs, especially in microwave. It can completely 
replace the 8566B, but I'm quite fond of the 8566B, I can operate it 
blind folded, it's like an old friend and I would really like to fix it.


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