When I played with a 251 years ago we had issues when the batteries used
to give a reference voltage died. If you find batteries on one of your
252 boards--swap them/it out (it could be a watch battery or a battery
pack--you could probably find replacements at DigiKey). The op-amps are
usually cheap enough to swap out too (number escapes me now).
On 12/8/2014 3:49 PM, Donald Chipley wrote:
> Hi Kendra,
> There are many high voltages here, as you likely know by now. Be careful!
> Check BEE in the back. There should be 5 green lights for the input voltages,+90, +15,-15, +5 and 0 to62. I don't think you can measure these directly. Also there is a transformer at the right side. Check input and output on it.
> When you checked potentials to the lenses did you check at the lens end of the wire or other. You can also check the lenses for leakage with an insulation tester or Megger. These charge the lenses to high voltage, don't go too high, and can show a current leak that won't show IP with a multimeter, I.e. good isolation at 9 v from multi meter, but not at 1000 V. The pots maxed out makes me think that a correct voltage isn't getting to the lenses or is leaking at the lenses.
> New Address: [log in to unmask]
> Don Chipley
> Queen's Facility for Isotope Research
> Dept. of Geol.
> Queen's University
> 36 Union Street
> Kingston, Ont. CANADA K7M 1G2
> PH 613-533-2016
> From: Stable Isotope Geochemistry [[log in to unmask]] on behalf of Kendra Chritz [[log in to unmask]]
> Sent: Monday, December 08, 2014 4:05 PM
> To: [log in to unmask]
> Subject: MAT 252 focusing struggles
> Hi everyone,
> We've had a long and exhausting struggle with our MAT 252. We've been trying to return to normal functionality after a power outage months ago. So far, we've cleaned the source and rebuilt it, replaced some old parts on boards in the source controller, replaced the magnet current controller, tested the D/A converter board (and also the amplifiers and the data logger boards). Everything appears to have normal functionality, but we cannot get a signal higher than 30mV of 44 on cup 2 (we should be getting about 1,500mV at the settings we have). No measured shorts in the source, no leakage current, brand new filament.
> We've made many passes at focusing the instrument, but we just can't get the signal up. We've even gone so far as to install a test cable for the high voltage boards and measure readouts directly from the potentiometers on BEF while adjusting them, and they all seem to give the appropriate voltage to the lenses. Voltage is good to box, trap and cathode.
> I should also add that many of the pots on BEF are maxed out, which seems strange to me. We can't get through a mass calibration because the voltage is too low.
> Ref gas on both conflo and dual inlet peripherals are giving the same results.
> Is there something I'm missing? Is there anything else I should check?
> Kendra Chritz
> Department of Biology
> University of Utah
> 257 South 1400 East, Rm 201
> Salt Lake City, UT 84112
> lab: 801.585.0415<tel:801.585.0415>
> cell: 206.719.3440<tel:206.719.3440>
> fax: 801.581.4668<tel:801.581.4668>