I have an HP-5216A that I got at the local flea market. One tube is bad
and one driver.
I found the drivers (they're special HP chips), but now I see it has
about 10mA leakage current to ground. I've removed everything on the
primary side and it seems to be the transformer. There's a slight chance
I pinched a wire in the transformer cage but I haven't had the energy to
try once more taking the transformer out. Oh, and I had to fabricate my
own power connector as it's really old. (That's not the source of the
leak as the current stops when I remove the fuse.)
http://wa5znu.org/2009/08/hp5216a/
Leigh/WA5ZNU
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.
Cheers,
Magnus
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