[time-nuts] HP 5061A problem

wje wje at quackers.net
Mon Aug 18 13:42:53 EDT 2008


If you install the second unit, your 5061A still won't work. +20v at the 
sensor output will signal the ion current monitor to shut down the 
electron multiplier supply.

If you have some high-value resistors around, can you make up a test 
200M resistor string? If so, see what happens when that's connected 
across 4 & 5 of the first 3500 v supply.

However, even with the failure case you describe with the first unit, 
I'd expect your 5061A to still work at least for a short time. Do you 
have beam current? If not, you might have other problems as well. Check 
the voltage at A15 pin 4. You should have +18 v or so. If not, more 
troubleshooting is in order.

The danger running without a working ion pump, though, is that at 
eventually you'll damage the electron multiplier.

Bill Ezell
----------
They said 'Windows or better'
so I used Linux.



Morris Odell wrote:
> Hi all,
>
> My 5061A has failed and I've isolated the problem to a faulty A18, the +3500 
> volt ion pump power supply.
>
> The existing one has almost certainly has had the internal 200M resistor go 
> open as the output voltage is about 5 kV and it does not decay quickly when 
> the power is off.  The output voltage to the current sensing circuit is 0.
>
> I have a replacement which I suspect is faulty - when energised from a +18 
> volt source it only produces 2 kV which decays quickly and the sensor output 
> is +20 when the thing is unloaded. That 200M resistor may have gone low! Is 
> this one worth installing ie: will +2 kV pump enough ions?
>
> So I'm looking for a replacement or advice from anyone who may have 
> attempted to repair one.
>
> If anyone has a parts donor of course I'd be happy to pay appropriately 
> including shipping down here to Australia.
>
> Morris 
>
>
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