[time-nuts] HP5328A repair experience

Magnus Danielson magnus at rubidium.dyndns.org
Mon Sep 7 21:00:56 UTC 2009

Fellow Time-nuts,

Some time back I was given a HP5328A that was working well, but started 
eating fuses. Fortunatly all manuals came with it.

It does eat fuses, but I failed to detect why at first. I went down some 
dead ends debug-wise, just to show that I am a bit rusty, but time to 
polish the rust of then...

In the end, the negative rail cap had shorted out. Nothing obviously 
wrong with that side. The way that the PCB trails work, there is a 
separate PCB trail to the negative side of that cap, and that had bruned 
straight off so the rest of the negative side was almost working.

Replacing both 4500 uF 35 VDC caps by RIFA 6800 uF 40 VDC PEH200 caps 
(works perfect as drop-in replacement as terminal screws and body size 
matches very well).

Power up and everything checks out fine. Just... works.

I have option 020 and 040 in mine, so it will do the funky jittered 
clock interpolation on averaging while achieving 10 ns singel-shot 
resolution from it's 100 MHz oscillator compared to 100 ns from the 
standard 10 MHz counting clock. I actually have a couple of 010 option 
boards with 10811 oscillators on them.

While it is not by any means my best counter, it's nice to see it 
running again.

So, hopefull someone apprechiate this little notice. Call it a distant 
echo from the past if you so wish.


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