[time-nuts] HP5328A repair experience

Leigh L. Klotz, Jr WA5ZNU Leigh at WA5ZNU.org
Fri Sep 11 06:13:12 UTC 2009

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.)


> 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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