Dear Gerry,

Good to see you last week.  I think the autocorrect is putting an "m" in 
front of everything.  The maximum filament current should be 5A (amps) 
and the high voltage 3000 V (volts).



On 12/01/2016 10:33 AM, gerard olack wrote:
> HI Andy--
> 1.  The heating current is 5mA, the emission sits on top of that. It is
> current limited--so the bad batch of filaments that went out a while ago
> looked like they might have been too thick and carried too much
> current--so the over all current limit was hit before you got good
> emission. If the leads are (close to) touching in the source, then the
> current bleeds thru that way.  Probably not a problem for you  Also I
> remember hearing about a bad batch of source heaters--they would leave a
> deposit on the insulators--so a small leak to ground at voltage.
> 2.  Our set up has the HV showing in Volts--and it goes from 0 to 3000
> mV.  So it should go all the way to 0 mV.  You can even check for
> problem with voltages at say 1000 mV?  Everything should float on the
> hV, which, at least according to the readbacks, bounces around a
> little.  It may also float a little away from your ground--depending on
> what you're using for ground--but that shouldn't be much.
> good luck
> gerry
> On 1/12/2016 10:38 AM, Andrew Schauer wrote:
>> Greetings list,
>> Two questions:
>> 1) Does anyone know what the current range THROUGH the filament is
>> supposed to be? I am not referring to the emission (~ 1.0 mA). We are
>> having a complete loss of signal and right now it looks like the
>> current through the filament is not varying as a function of the
>> potentiometer (physical potentiometer on the face of the instrument).
>> When I vary the potentiometer I see no variation for most of the
>> travel and the a sudden drop to zero volts (across a resistor that
>> escapes me at this moment).
>> 2) For the Isodat software 2.x on windows xp, if I vary the HV
>> [steps], from 0 to 3000, what should I expect in terms of real high
>> voltage variation? For example, if I measure voltage between (yes
>> using appropriate high voltage probes and caution) ground and "col".
>> To call out two of you that may be listening (Peter and Christie), we
>> talked at the clumped conference about this loss of signal issue. The
>> source connections are all sound (I vented it and checked each
>> connection which were all very solid). I also measured no connection
>> between any feedthrough and another (apart from the 0.2 ohms for the
>> filament). I also observe expected magnet strength when I hold a metal
>> object near the magnet during hysteresis.
>> Thank you.
>> andy
>> --
>> Andrew Schauer
>> 206.543.6327
>> [log in to unmask] <mailto:[log in to unmask]>
>> _


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