Profile: RainaCardone

Your personal background.
2. To install an early 5 speed transmission into a 1981 (& later) bike means
a different input shaft on the transmission is needed; and, you will have to re-shim the transmission,
etc. It will then work OK. Without hesitation we have recommended
Avery Appliance Service to… Deal with a company that is well established and known for the work they have
completed in their industry - a commercial entity, for
instance - and who can produce proof that other clients
have positive feedback about their service and knowledge.
Not wanting to test this under vacuum (in part because my vacuum plumbing isn't ready
and to avoid possible damage to my limited collection of
ion gauge tubes), I decided that it would be nice to have
a means of simulating an ion gauge tube without an ion gauge
tube since there is no way to power one without
a vacuum below about 1x10-3 Torr. While designed specifically for the GP-270, this basic approach should work for other ion gauge controllers.


Attach the auto head light bulb to the filament pins of the ion gauge
tube connector. The circuit I'm going to build simulates
the behavior of the common Bayard-Alpert (hot
filament) ion gauge tube using light bulbs and photodiodes.

The MKS-909 operates exactly like other ion gauges based on the Bayard-Alpert except that everything is
miniaturized. While many common ion gauges consist of a (usually) fragile glass tube sensor and separate display/readout, the MKS-909 MIG (Miniature
Ion Gauge) Transducer puts all of that in a compact relatively robust unit with overall dimensions less the 3x4x5
inches and weighing in at about 1 pound - smaller and lighter than the typical
ion gauge tube in protective enclosure alone. This
provides both a load to test the filament power supply
as well as a warmup delay (due to its filament heating) to test the interlock circuits of the ion gauge controller.

The MKS-909 contains a stainless steel ion gauge "tube" (replaceable) and complete electronics to drive it
that runs on 24 VDC. A photodiode monitoring the output
of the light bulb drives a current source which simulates the emission current of the ion gauge tube.


The ion gauge tube filament is a single filament 12 V auto head light bulb.
Having done preliminary testing of my turbo pump (see the section: A
Small High Vacuum System), I acquired a Granville-Phillips model
270 ion gauge controller (GP-270). Where the unit also includes a
thermocouple vacuum gauge or gauges, these can be tested
separately either using a tester or under vacuum, and then with the ion gauge section. The simulated
emission current passes through the LED of an opto-coupler whose photodiode is used to
provide the simulated ion current from the ion gauge collector electrode to the high sensitivity
(electrometer) amplifier of the controller. Power down and
make sure the voltages on all the ion gauge tube pins have dropped to near
zero. Depending on the design of the controller, the
actual voltages may vary but their difference should be close to the spec for the ion gauge tube - typically about 150 VDC positive on the
grid. The operation manual can be downloaded via the MKS Instruments Web site but a Web search for "HPS Series 909 Miniature Ionization Gauge" should return a direct link.
The manual includes complete programming information.

But if you've forgotten how it works, there's even an instant theory section in the manual.
Even if they had totally separate terminals, there might be
some thermionic emission or discharge current flow between the two filaments of the light bulb (depending on whether it was
evacuated or gas-filled). Note that a dual beam head light bulb CANNOT be used
because the two filaments aren't isolated (for filament and grid).

Install the 100 ohm resistor or your second auto head light bulb between the two grid pins.
A second light bulb is used for the grid to test the "degas" function. Power up and test out the degas
function. Adjustments permit the "sensed" pressure to be varied to test the controller's
response on each range and its autoranging
circuits. Without feedback (filament current to emission current), it may not
be possible to keep it on but there may be a range
of positions of the external pot and/or emission pot where the
brightness of the filament can be varied. For example, exposure
to increased insecticide concentrations may lead to elevated
tissue concentrations, respiratory distress, and changes in development.
If you're having trouble with a machine but aren't sure if,
for example, you need to get a washing machine repair or if you should just
buy a new washer, appliance professionals will be able to asses the problem
and provide you with the information that you need to make a decision.

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